Getting Start With FreeMarker

I want to make a video of an IT tutorial, can you arrange the text content of the video tutorial for me according to the content of the website. Let’s start with the freemarker tutorial, and you first give me an overview of the content to be explained.

Of course, according to your request, I have listed for you a video content outline of the FreeMarker tutorial. You can make corresponding video tutorials based on this outline.

1. Introduction to FreeMarker 1.1. What is FreeMarker? 1.2. Advantages and application scenarios of FreeMarker
2. FreeMarker installation and environment configuration 2.1. Install Java environment 2.2. Download and install FreeMarker 2.3. Configure FreeMarker development environment
3. Basic syntax of FreeMarker 3.1. Labels and instructions 3.2. Variables and expressions 3.3. Comments 3.4. String operations 3.5. Number operations 3.6. Date and time operations
4. Process control of FreeMarker 4.1. Condition judgment 4.2. Loop 4.3. List processing 4.4. Mapping processing
5. Macros and functions of FreeMarker 5.1. Define macros 5.2. Call macros 5.3. Built-in functions 5.4. Custom functions
6. FreeMarker’s data model 6.1. Introduction to data model 6.2. Data type 6.3. Data model instance
7. FreeMarker and Java integration 7.1. Java object access 7.2. Java method call 7.3. JavaBeans integration
8. FreeMarker actual combat case 8.1. Website template generation 8.2. Email template generation 8.3. PDF report generation
9. Advanced topics in FreeMarker9.1. Custom directives9.2. Configuration and tuning9.3. Internationalization support
10. FreeMarker Resources and Further Learning10.1. Official Documentation and Tutorials10.2. Community and Q&A10.3. Recommended Books and Courses

Please make corresponding video tutorials according to the above outline. If you have any questions or need further assistance, please feel free to contact me. Good luck with your video tutorial!

Please explain in detail what is FreeMarker?

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FreeMarker is a Java-based templating engine for dynamically generating text output. It is an open source software that follows the Apache license and is efficient, flexible, customizable, and easy to learn and use.

In web applications, FreeMarker is usually used as the View layer component in the MVC (Model-View-Controller) architecture, that is, the view template engine. Its main function is to receive the data model and render the data into the view template, and finally generate HTML, XML, JSON, CSV and other output.

FreeMarker’s templates are based on text files that contain text and placeholders that are replaced with dynamically generated data. Placeholders in templates can be in the form of variables, expressions, tags, etc., all of which are parsed and rendered by the FreeMarker engine.

The syntax of FreeMarker is similar to Java, but it is not a programming language, but a templating language. It provides a wealth of grammatical elements, including conditional judgment, loops, variable definitions, macro definitions, function calls, etc., which can easily process and display data.

In short, FreeMarker is a very useful template engine, which is widely used in dynamic generation scenarios such as web applications, emails, reports, documents, etc. Its high efficiency, flexibility and customizability enable developers to quickly and easily generate various kind of output.

Please explain in detail the advantages and application scenarios of FreeMarker

As a template engine, FreeMarker has many advantages and applicable scenarios. Let’s explain it in detail below:

1. Efficient: FreeMarker is written in Java language and uses highly optimized algorithms, which can quickly render large amounts of data.
2. Flexible: FreeMarker supports a variety of data formats, including JavaBean, Map, List, array, etc., and supports custom data types and methods.
3. Customizable: FreeMarker provides many custom instructions and functions, allowing developers to expand and customize the template engine according to their needs.
4. Easy to learn and use: FreeMarker syntax is similar to Java, easy to understand and learn, and also provides rich documentation and examples.
5. Cross-platform: FreeMarker can run on any platform that supports Java, such as Windows, Linux, macOS, etc.

Based on the above advantages, FreeMarker can exert its power in many scenarios. The following are some common application scenarios:

1. Web application: FreeMarker can be used as a View layer component in the MVC architecture to dynamically generate output such as HTML, XML, and JSON, and realize the rendering of Web pages.
2. Email template: FreeMarker can be used to generate email templates, separate email content and format from business logic, and meet the needs of fast batch sending of emails.
3. PDF report: FreeMarker can be used with third-party Java libraries, such as iText, Apache POI, etc., to generate reports in PDF format.
4. Document generation: FreeMarker can be used to generate various documents, such as Word, Excel, HTML, etc., to meet the needs of automatic document generation.

In short, FreeMarker is a powerful, flexible, and easy-to-use template engine, suitable for data rendering and dynamic generation in various scenarios.

Please explain in detail the installation and environment configuration of FreeMarker Install the Java environment

Installing and configuring the Java environment is the prerequisite for using FreeMarker. Below we will introduce how to install the Java environment and FreeMarker respectively.

1. Install the Java environment

Before installing FreeMarker, you need to install the Java environment first. Here are the steps to install the Java environment:

1.1. Download the Java installer

First, download the Java installer from the official website, and select the version that matches your operating system and hardware architecture. The installer is usually an .exe or .dmg file that you double-click to open to start the installation.

1.2. Install Java

After launching the installer, follow the prompts to install. Usually, you just need to select the default options. After the installation is complete, you need to set the Java environment variable so that the operating system can correctly identify the Java installation path.

1.3. Verify Java installation

Once the installation is complete, you can verify that Java was installed correctly by running the following command:

Copy codejava -version

If Java has been installed correctly, information such as the Java version number will be displayed. If the java command is not found or the version number is incorrect, it means that the Java installation failed. Please check whether the installation process is correct.

2. Install FreeMarker

After installing the Java environment, you can start installing FreeMarker. Here are the steps to install FreeMarker:

2.1. Download FreeMarker installation package

First, download the FreeMarker installation package from the official website and select the version that matches your operating system. The installation package is usually a .zip or .tar.gz file, which can be downloaded and decompressed to any directory.

2.2. Configure the FreeMarker environment

After decompression, enter the FreeMarker installation directory, find the lib folder, and add the freemarker.jar file to the classpath in your Java project. This step can be done in many ways, such as adding the -classpath parameter when compiling with javac on the command line, or using development tools such as Eclipse to configure.

2.3. Verifying the FreeMarker installation

After the installation is complete, you can write a simple FreeMarker template and execute the template with a Java program to verify whether FreeMarker has been installed correctly. For the specific implementation process, please refer to the official FreeMarker documentation and sample programs.

In short, installing and configuring the Java environment and FreeMarker are the prerequisites for using FreeMarker. Only when these two components are installed and configured correctly can FreeMarker be used for template rendering smoothly.

Please explain in detail the installation and environment configuration of FreeMarker Download and install FreeMarker

FreeMarker is an open source template engine. The process of installing and configuring FreeMarker is relatively simple. Below we will introduce the steps to download and install FreeMarker in detail:

1. Download FreeMarker

First, download the FreeMarker installation package from the official website http://freemarker.apache.org/, select the version that matches your operating system, and unzip it to any directory after downloading. The installation package is usually a .zip or .tar.gz file.

2. Import the FreeMarker library

To use FreeMarker in Java development, you need to add the freemarker.jar file to the classpath in your Java project. This step can be done in many ways, such as adding the -classpath parameter when compiling with javac on the command line, or using development tools such as Eclipse to configure.

3. Write template files

Create a template file with any name but usually with a .ftl extension. In the template file, you can use various syntax elements provided by FreeMarker, such as variables, expressions, tags, etc. to build templates.

4. render template

Write Java code to render the template through the API provided by FreeMarker. For the specific implementation process, please refer to the official FreeMarker documentation and sample programs. When rendering a template, you need to pass the path of the template file into the FreeMarker engine as a parameter, and pass parameters such as data model and output stream into the rendering method, and the FreeMarker engine will generate output according to the template and data model.

5. verify installation

After the installation and configuration are complete, you can write a simple FreeMarker template and execute it with a Java program to verify that FreeMarker has been installed correctly. For the specific implementation process, please refer to the official FreeMarker documentation and sample programs.

In short, downloading and installing FreeMarker is very simple. You only need to download and unzip the installation package from the official website, add freemarker.jar to the Java project, and then you can use FreeMarker for template rendering. When writing and using templates, you need to pay attention to the correctness of the syntax and the rationality of the data model, all of which need to refer to the FreeMarker documentation and sample programs.

Please explain in detail the installation and environment configuration of FreeMarker to configure the FreeMarker development environment

Configuring the FreeMarker development environment is an important step in using FreeMarker. Below we will introduce in detail how to configure the FreeMarker development environment:

1. Import the FreeMarker library

To use FreeMarker in Java development, you need to add the freemarker.jar file to the classpath in your Java project. This step can be done in many ways, such as adding the -classpath parameter when compiling with javac on the command line, or using development tools such as Eclipse to configure.

If you use Maven to build your project, you can add the following dependencies in your pom.xml file:

xmlCopy code<dependency>
    <groupId>org.freemarker</groupId>
    <artifactId>freemarker</artifactId>
    <version>2.3.30</version>
</dependency>

This will automatically download and import the FreeMarker library.

2. Configure FreeMarker properties

When using FreeMarker in Java code, some configuration is required so that the FreeMarker engine can correctly parse and render templates. It can be configured with the following code:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_30);
cfg.setDirectoryForTemplateLoading(new File("templates"));
cfg.setDefaultEncoding("UTF-8");

Among them, the Configuration class is the core class of FreeMarker, which is used to configure various properties of the FreeMarker engine. In this example, the version number of FreeMarker, the directory path of the template file and the default encoding method are set.

3. Create a data model

When using FreeMarker for template rendering, data needs to be passed to the FreeMarker engine and encapsulated as a data model. A data model can be created with the following code:

javaCopy codeMap<String, Object> data = new HashMap<String, Object>();
data.put("name", "FreeMarker");
data.put("version", "2.3.30");

In this example, Java’s Map data structure is used to encapsulate the data model, and more key-value pairs can be added as needed.

4. render template

After you have the configuration and data model, you can use the FreeMarker engine to render the template. Template rendering can be done with the following code:

javaCopy codeTemplate template = cfg.getTemplate("hello.ftl");
Writer out = new OutputStreamWriter(System.out);
template.process(data, out);

In this example, use the Template class to load the template file and create an output stream to output the rendering result to the console.

5. Verify the development environment

After configuring the development environment, you can write a simple FreeMarker template and execute the template with a Java program to verify whether FreeMarker has been configured correctly. For the specific implementation process, please refer to the official FreeMarker documentation and sample programs.

In short, configuring the FreeMarker development environment requires steps such as setting FreeMarker properties, creating data models, and rendering templates. These steps need to be completed by referring to FreeMarker documentation and sample programs. Only when the development environment is configured correctly can FreeMarker be used for template rendering smoothly.

Please explain in detail the basic syntax tags and instructions of FreeMarker

The basic syntax tags and instructions of FreeMarker are an important part of using FreeMarker for template rendering. Below we will introduce the basic syntax tags and instructions of FreeMarker in detail:

1. variable

FreeMarker uses ${} tags to represent variables, which can be used in templates to output values ​​in the data model, for example:

bashCopy codeHello, ${user.name}!

In this example, the ${} tag is used to output the value of user.name in the data model.

2. expression

FreeMarker supports a variety of expressions, such as arithmetic expressions, logical expressions, comparison expressions, etc., which can be used to process and display data. Here are some common expressions:

2.1. Arithmetic expressions

lessCopy code${a + b}  // 加法
${a - b}  // 减法
${a * b}  // 乘法
${a / b}  // 除法
${a % b}  // 取模

2.2. Logical expressions

lessCopy code${a and b}  // 与
${a or b}  // 或
${not a}  // 非

2.3. Comparing expressions

lessCopy code${a == b}  // 相等
${a != b}  // 不等
${a < b}  // 小于
${a <= b}  // 小于等于
${a > b}  // 大于
${a >= b}  // 大于等于

3. instruction

FreeMarker also provides a variety of instructions that can be used to control the rendering and display of templates. Here are some common directives:

3.1. if instruction

arduinoCopy code<#if condition>
    // 如果条件成立，执行这里的代码
<#else>
    // 如果条件不成立，执行这里的代码
</#if>

3.2. list command

arduinoCopy code<#list items as item>
    // 遍历items列表，每次循环将当前元素赋值给item
</#list>

3.3. assign command

arduinoCopy code<#assign name = value>

3.4. include directive

arduinoCopy code<#include "filename.ftl">

3.5. function directive

arduinoCopy code<#function name (arg1, arg2, ...)>
    // 函数体
</#function>

When using instructions, you need to pay attention to the correctness of the grammar and the rationality of the way of use, all of which need to refer to the FreeMarker documentation and sample programs.

In short, the basic grammar tags and instructions of FreeMarker are an important part of using FreeMarker for template rendering. Only by mastering these basic grammars can better template rendering and data display be performed.

Please explain in detail the basic grammar variables and expressions of FreeMarker

The basic grammatical variables and expressions of FreeMarker are an important part of using FreeMarker for template rendering. Below we will introduce the basic grammatical variables and expressions of FreeMarker in detail:

1. variable

FreeMarker uses ${} tags to represent variables, which can be used in templates to output values ​​in the data model. The syntax format is as follows:

bashCopy code${variable}

Among them, variable is a variable name in the data model, which can be a simple variable name or a compound variable name. For example:

arduinoCopy code${name}  // 输出简单变量name的值
${user.name}  // 输出复合变量user.name的值

2. expression

FreeMarker supports a variety of expressions, which can be used to process and display data. Here are some common expressions:

2.1. Arithmetic expressions

FreeMarker supports common arithmetic operators such as addition, subtraction, multiplication, division, and modulus. The syntax format is as follows:

lessCopy code${a + b}  // 加法
${a - b}  // 减法
${a * b}  // 乘法
${a / b}  // 除法
${a % b}  // 取模

Among them, a and b are variable names, which can be simple variable names or compound variable names.

2.2. Logical expressions

FreeMarker supports logical operators such as AND, OR, and NOT. The syntax format is as follows:

lessCopy code${a and b}  // 与
${a or b}  // 或
${not a}  // 非

Among them, a and b are variable names, which can be simple variable names or compound variable names.

2.3. Comparing expressions

FreeMarker supports comparison operators such as equal, not equal, less than, less than or equal to, greater than and greater than or equal to, etc. The syntax format is as follows:

lessCopy code${a == b}  // 相等
${a != b}  // 不等
${a < b}  // 小于
${a <= b}  // 小于等于
${a > b}  // 大于
${a >= b}  // 大于等于

Among them, a and b are variable names, which can be simple variable names or compound variable names.

In short, the basic grammar variables and expressions of FreeMarker are an important part of template rendering with FreeMarker. Only by mastering these basic grammars can template rendering and data display be better performed. When using variables and expressions, you need to pay attention to the correctness of variable names and the rationality of expressions, all of which need to refer to FreeMarker’s documentation and sample programs.

Please explain the basic syntax annotations of FreeMarker in detail

FreeMarker’s basic syntax comments are an important part of template development using FreeMarker. They can be used to comment template code and improve code readability. Below we will introduce FreeMarker’s basic syntax comments in detail:

1. line comment

FreeMarker supports line comments, starting with a # sign and ending at the end of the line. Line comments are often used to add comments and debugging information in templates. For example:

bashCopy code<#-- 这是一个行注释 -->

2. block comment

FreeMarker also supports block comments, surrounded by <#– and –>, block comments can span lines, and can be nested. Block comments are typically used to comment larger blocks of code, for example:

luaCopy code<#--
这是一个
多行注释
-->

When using annotations, you need to pay attention to the following points:

• Comments are only used in template files and will not affect rendering results.
• Comments can be used in labels, expressions, and directives to increase code readability and ease of maintenance.
• Annotations should not affect the performance of templates, and you should avoid using too many annotations when rendering large amounts of data.

In short, FreeMarker’s basic syntax comments are an important part of template development using FreeMarker, which can be used to comment template code and improve code readability. When using annotations, you need to pay attention to the grammatical format and usage scenarios of annotations to increase the maintainability and performance of the code.

Please explain in detail the basic syntax string manipulation of FreeMarker

The basic syntax string operation of FreeMarker is an important part of template rendering using FreeMarker, which can be used to process and display strings. Below we will introduce the basic syntax string operations of FreeMarker in detail:

1. string concatenation

FreeMarker uses the + sign to indicate string concatenation, and multiple strings can be spliced ​​together, for example:

rubyCopy code${"Hello," + " " + "world!"}

2. string length

FreeMarker uses ?size to represent the length of the string, and can calculate the number of characters in the string, for example:

rubyCopy code${"hello world"?size}

In this example, the length of the “hello world” string is calculated and the result is 11.

3. String interception

FreeMarker uses ?substring to represent string interception, which can intercept substrings within a specified range. The syntax format is as follows:

scssCopy code${string?substring(beginIndex, endIndex)}

Among them, string is the string to be intercepted, beginIndex is the starting position of the interception, and endIndex is the end position of the interception (the character at this position is not included). For example:

rubyCopy code${"hello world"?substring(0, 5)}  // 输出"hello"

4. string replacement

FreeMarker uses ?replace to represent string replacement, which can replace a substring in a string with another substring. The syntax format is as follows:

scssCopy code${string?replace(substring, replacement)}

Among them, string is the character string to be replaced, substring is the substring to be replaced, and replacement is the substring after replacement. For example:

rubyCopy code${"hello world"?replace("world", "FreeMarker")}  // 输出"hello FreeMarker"

5. string case conversion

FreeMarker uses ?lower_case and ?upper_case to represent the case conversion of strings, which can convert strings to lowercase or uppercase. For example:

shellCopy code${"Hello, World!"?lower_case}  // 输出"hello, world!"
${"Hello, World!"?upper_case}  // 输出"HELLO, WORLD!"

When using string operations, you need to pay attention to the following points:

• String operations are only available for variables of type string.
• String operations are often used to display and manipulate data, such as manipulating text when rendering HTML pages, or formatting data when exporting data.
• String operations can be nested for more complex string manipulation.

In short, the basic grammar string operation of FreeMarker is an important part of using FreeMarker for template rendering. Only by mastering these basic grammars can template rendering and data display be better performed. When using string operations, you need to pay attention to the correctness of the syntax and the rationality of the way of use, all of which need to refer to the FreeMarker documentation and sample programs.

Please explain in detail the basic grammatical number operations of FreeMarker

FreeMarker’s basic grammatical digital operations are an important part of template rendering using FreeMarker, which can be used to process and display numbers. Below we will introduce FreeMarker’s basic grammatical digital operations in detail:

1. number formatting

FreeMarker uses ?string to represent number formatting, which can convert numbers to strings in the specified format. The syntax format is as follows:

luaCopy code${number?string(format)}

Among them, number is the number to be formatted, format is the format string, and some placeholders can be used to represent different parts of the number. For example:

cCopy code${1234567.89?string("#,##0.00")}  // 输出"1,234,567.89"

In this example, the format string “#,##0.00” is used to convert the number to the form of a thousand separator and retain 2 decimal places.

2. Numbers are rounded

FreeMarker uses ?round to indicate the rounding of numbers, which can round numbers according to the specified number of digits, for example:

scssCopy code${1234567.8956?round(2)}  // 输出1234567.90

In this example, the number is kept to 2 decimal places and rounded according to the rounding rules.

3. digital comparison

FreeMarker uses comparison operators to represent the comparison of numbers, such as equal, not equal, less than, less than or equal to, greater than and greater than or equal to, etc. The syntax format is similar to string operations, for example:

lessCopy code${a < b}  // 小于
${a == b}  // 相等
${a > b}  // 大于

Among them, a and b are variables of numeric type.

When using digital operations, you need to pay attention to the following points:

• Numeric operations are only available for variables of numeric type.
• Numeric operations are often used to represent and manipulate data, such as formatting data when rendering a chart, or rounding data when calculating.
• Numeric operations can be nested for more complex numerical manipulation.

In short, the basic syntax and digital operation of FreeMarker are an important part of using FreeMarker for template rendering. Only by mastering these basic syntax can template rendering and data display be performed better. When using digital operations, you need to pay attention to the correctness of the syntax and the rationality of the way of use, all of which need to refer to the FreeMarker documentation and sample programs.

Please explain in detail the basic syntax of FreeMarker date and time operations

FreeMarker’s basic grammatical date and time operations are an important part of using FreeMarker for template rendering, which can be used to process and display dates and times. Below we will introduce FreeMarker’s basic grammatical date and time operations in detail:

1. date formatting

FreeMarker uses ?string to represent date formatting, which can convert the date to a string in the specified format. The syntax format is as follows:

luaCopy code${date?string(format)}

Among them, date is the date to be formatted, format is a format string, and some placeholders can be used to represent different parts of the date. For example:

luaCopy code${date?string("yyyy-MM-dd HH:mm:ss")}  // 输出"2023-04-27 14:30:00"

In this example, use the “yyyy-MM-dd HH:mm:ss” format string to convert the date to a string in the specified format.

2. date calculation

FreeMarker uses ?time_delta and ?date_delta to represent date calculations, and can add and subtract dates, for example:

luaCopy code${date?time_delta(1, "days")?string("yyyy-MM-dd")}  // 输出"2023-04-28"
${date?date_delta(1, "years")?string("yyyy-MM-dd")}  // 输出"2024-04-27"

In this example, the ?time_delta and ?date_delta functions are used to add and subtract dates, and the ?string function is used to convert the date to a string in the specified format.

3. get date and time

FreeMarker uses ?date and ?time to represent date and time, and the current date and time can be obtained. For example:

luaCopy code${.now?date?string("yyyy-MM-dd")}
${.now?time?string("HH:mm:ss")}

In this example, the ?date and ?time functions are used to obtain the current date and time, and the ?string function is used to convert the date and time into a string in the specified format.

When using date and time operations, you need to pay attention to the following points:

• Date and time operations are only available for date type variables.
• Date and time operations are typically used to display and manipulate date and time data, such as formatting dates when rendering a calendar, or performing addition and subtraction operations when calculating dates and times.
• Date and time operations can be nested for more complex date and time manipulation.

In short, FreeMarker’s basic grammar date and time operations are an important part of using FreeMarker for template rendering. Only by mastering these basic grammars can better template rendering and data display be performed. When using date and time operations, you need to pay attention to the correctness of the syntax and the rationality of the way of use, all of which need to refer to the FreeMarker documentation and sample programs.

Please explain in detail FreeMarker’s process control condition judgment

FreeMarker’s process control condition judgment is an important part of template rendering using FreeMarker. Different code blocks can be executed according to different conditions. Below we will introduce FreeMarker’s process control condition judgment in detail:

1. if statement

The if statement can be used to execute different code blocks according to different conditions. The syntax format is as follows:

lessCopy code<#if condition>
    code block1
<#elseif condition2>
    code block2
<#else>
    code block3
</#if>

Among them, condition is the conditional expression to be judged, which can be any expression. If condition is true, execute code block1; if condition is false, judge condition2, if true, execute code block2; otherwise execute code block3.

For example:

lessCopy code<#if score >= 90>
    <p>优秀</p>
<#elseif score >= 80>
    <p>良好</p>
<#elseif score >= 70>
    <p>一般</p>
<#else>
    <p>不及格</p>
</#if>

In this example, different code blocks are executed according to different fractional segments.

2. switch statement

The switch statement can be used to execute different code blocks according to different values. The syntax format is as follows:

lessCopy code<#switch value>
    <#case condition1>
        code block1
    <#case condition2>
        code block2
    <#default>
        code block3
</#switch>

Among them, value is the value to be judged, which can be any value. If value is equal to condition1, execute code block1; if value is equal to condition2, execute code block2; otherwise execute code block3.

For example:

javascriptCopy code<#switch dayOfWeek>
    <#case 1>
        <p>星期一</p>
    <#case 2>
        <p>星期二</p>
    <#case 3>
        <p>星期三</p>
    <#case 4>
        <p>星期四</p>
    <#case 5>
        <p>星期五</p>
    <#default>
        <p>周末</p>
</#switch>

In this example, different code blocks are executed according to different days of the week.

When using conditional judgment statements, you need to pay attention to the following points:

• Conditional judgment statements can be nested to implement more complex logic.
• Conditional judgment statements can be used with variables, strings, numbers and expressions to achieve more application scenarios.
• Conditional judgment statements can be used together with other flow control statements (such as loop statements) to achieve more complex logic and functions.

In short, FreeMarker’s process control condition judgment is an important part of template rendering using FreeMarker. Only by mastering these basic grammars can template rendering and data display be better performed. in terms of use

please continue

When judging a statement, you need to pay attention to the correctness of the grammar and the rationality of the usage, all of which need to refer to the FreeMarker documentation and sample programs. In practical applications, it is necessary to select appropriate conditional judgment statements according to specific scenarios to achieve expected functions and effects.

Please explain FreeMarker’s flow control list processing in detail

FreeMarker’s process control list processing is an important part of using FreeMarker for template rendering, which can be used to process and display the list. Below we will introduce FreeMarker’s process control list processing in detail:

1. foreach loop

The foreach loop can be used to traverse each element in the list, the syntax format is as follows:

lessCopy code<#list list as item>
    code block
</#list>

Among them, list is the list to traverse, and item is the name of each element, which can be any name. In the loop, use ${item} to represent the value of the current element.

For example:

bashCopy code<#list scores as score>
    ${score}<br>
</#list>

In this example, iterate over the score list and output each score.

2. index and item variables

In the foreach loop, you can use the index and item variables to represent the index and value of the current element. For example:

bashCopy code<#list scores as score>
    ${index + 1}. ${score}<br>
</#list>

In this example, output the index and value of each element in the scores list.

3. if statement and break instruction

In the foreach loop, you can use the if statement and the break instruction to perform conditional judgment and jump out of the loop. For example:

bashCopy code<#list scores as score>
    <#if score < 60>
        <p>不及格</p>
        <#break>
    </#if>
    ${score}<br>
</#list>

In this example, if the score is less than 60, output “Fail” and break out of the loop.

There are a few things to keep in mind when working with lists:

• List processing is usually used to display and process list data, such as traversing and processing lists when rendering tables.
• List processing can be nested to achieve more complex list processing and display.
• List processing can be used with other flow control statements (such as conditional judgment statements) to achieve more complex logic and functions.

In short, FreeMarker’s process control list processing is an important part of using FreeMarker for template rendering. Only by mastering these basic grammars can better template rendering and data display be performed. When using list processing, you need to pay attention to the correctness of the syntax and the rationality of the way of use, all of which need to refer to the FreeMarker documentation and sample programs.

Please explain FreeMarker’s flow control mapping processing in detail

FreeMarker’s process control mapping processing is an important part of using FreeMarker for template rendering, which can be used to process and display the mapping. Below we will introduce FreeMarker’s process control mapping processing in detail:

1. foreach loop

The foreach loop can be used to traverse each key-value pair in the map. The syntax is as follows:

bashCopy code<#list map?keys as key>
    ${key}: ${map[key]}<br>
</#list>

where map is the map to traverse and key is the name of each key, which can be any name. In the loop, use ${key} to represent the name of the current key and ${map[key]} to represent the value of the current key.

For example:

bashCopy code<#list user as key>
    ${key}: ${user[key]}<br>
</#list>

In this example, the user information map is traversed, and the name and value of each key-value pair are output.

2. if statement and else instruction

In mapping processing, you can use if statement and else instruction to perform conditional judgment and output default value. For example:

lessCopy code<#if user["age"]??>
    ${user["age"]}
<#else>
    未填写
</#if>

In this example, if the “age” key exists in the user information map, output the value of the key, otherwise output “not filled”.

When using mapping processing, you need to pay attention to the following points:

• Map processing is usually used to display and process map data, such as traversing and processing maps when rendering user information.
• Mapping processing can be nested to achieve more complex mapping processing and display.
• Mapping processing can be used together with other flow control statements (such as conditional judgment statements) to achieve more complex logic and functions.

In short, FreeMarker’s process control mapping processing is an important part of using FreeMarker for template rendering. Only by mastering these basic grammars can better template rendering and data display be performed. When using mapping processing, you need to pay attention to the correctness of the grammar and the rationality of the way of use, all of which need to refer to the documentation and sample programs of FreeMarker.

Please explain FreeMarker’s macros and function definition macros in detail

FreeMarker’s macros and function definition macros are an important part of using FreeMarker for template rendering. They can be used to define your own functions and code blocks. Below we will introduce FreeMarker’s macros and function definition macros in detail:

1. macro definition

Macro definitions can be used to define their own code blocks, which can be called multiple times in templates. The syntax format is as follows:

lessCopy code<#macro name [parameters]>
    code block
</#macro>

Among them, name is the name of the macro, and parameters is the parameter list of the macro, which can be any parameters. In a macro, you can use ${parameters} to represent the parameter value of the macro.

For example:

bashCopy code<#macro hello name>
    Hello, ${name}!
</#macro>

In this example, a macro named hello is defined, which accepts a name parameter and outputs “Hello, ${name}!”.

When calling a macro in a template, use the following syntax:

cssCopy code<@name parameter1=xxx parameter2=xxx ... />

Among them, name is the name of the macro, parameter1, parameter2, etc. are the parameter names of the macro, and xxx is the parameter value.

For example:

cssCopy code<@hello name="John" />

In this example, the macro called hello is called, passing in a name parameter, and outputs “Hello, John!”.

2. function definition macro

Function definition macros can be used to define their own functions, which can be called multiple times in the template. The syntax format is as follows:

lessCopy code<#function name [parameters]>
    code block
</#function>

Among them, name is the name of the function, and parameters is the parameter list of the function, which can be any parameter. In a function, use the return statement to return the value of the function.

For example:

sqlCopy code<#function add x y>
    <#return x + y>
</#function>

In this example, a function called add is defined that accepts two parameters x and y and returns the value of x+y.

When calling a function in a template, use the following syntax:

scssCopy code${name(parameter1, parameter2, ...)}

Among them, name is the name of the function, parameter1, parameter2, etc. are the parameter names of the function, which can be any expression.

For example:

scssCopy code${add(1, 2)}

In this example, the function named add is called with two parameters 1 and 2, and 3 is returned.

When using macros and functions to define macros, you need to pay attention to the following points:

• Macros and function definitions Macros are usually used to define your own functions and code blocks to achieve template reuse and modular development.
• Macros and function definitions Macros can be nested to implement more complex functions and code blocks.
• Macros and function definitions Macros can be used together with other flow control statements (such as conditional judgment statements) to implement more complex logic and functions.

In short, FreeMarker’s macros and function definition macros are an important part of using FreeMarker for template rendering. Only by mastering these basic grammars can better template rendering and data display be performed. When using macros and functions to define macros

Please explain FreeMarker’s macros and function call macros in detail

FreeMarker’s macros and function call macros are an important part of using FreeMarker for template rendering, and can be used to call custom functions and code blocks. Below we will introduce FreeMarker’s macros and function call macros in detail:

1. macro call

When calling a macro in a template, use the following syntax:

cssCopy code<@name parameter1=xxx parameter2=xxx ... />

Among them, name is the name of the macro, parameter1, parameter2, etc. are the parameter names of the macro, and xxx is the parameter value.

For example:

bashCopy code<#macro hello name>
    Hello, ${name}!
</#macro>

<@hello name="John" />

In this example, the macro called hello is called, passing in a name parameter, and outputs “Hello, John!”.

When calling a macro, flow control statements such as if statement and foreach loop can be used to realize more complex logic and functions.

2. function call

When calling a function in a template, use the following syntax:

scssCopy code${name(parameter1, parameter2, ...)}

Among them, name is the name of the function, parameter1, parameter2, etc. are the parameter names of the function, which can be any expression.

For example:

sqlCopy code<#function add x y>
    <#return x + y>
</#function>

${add(1, 2)}

In this example, the function named add is called with two parameters 1 and 2, and 3 is returned.

When calling a function, flow control statements such as if statement and foreach loop can be used to realize more complex logic and functions.

When using macros and function call macros, you need to pay attention to the following points:

• Macros and function calls Macros are usually used to call custom functions and code blocks to achieve template reuse and modular development.
• Macros and function calls Macros can be nested for more complex function and code block calls.
• Macros and function calls Macros can be used together with other flow control statements (such as conditional judgment statements) to implement more complex logic and functions.

In short, FreeMarker’s macros and function call macros are an important part of using FreeMarker for template rendering. Only by mastering these basic grammars can better template rendering and data display be performed. When using macros and function call macros, you need to pay attention to the correctness of the syntax and the rationality of the way of use, all of which need to refer to the FreeMarker documentation and sample programs.

Please explain FreeMarker’s macros and function builtins in detail

FreeMarker provides many built-in functions that can be used in macros and functions to achieve richer data manipulation and processing. Below we will introduce FreeMarker’s macro and function built-in functions in detail:

1. String manipulation functions

FreeMarker provides many string manipulation functions that can be used to process and manipulate strings, for example:

• length: Returns the length of the string.
• trim: Remove spaces from both ends of the string.
• substring: intercept part of the string.
• replace: Replace substrings in strings.
• split: Split the string into a list.

For example:

arduinoCopy code<#macro hello name>
    Hello, ${name?cap_first}!
</#macro>

${"hello world"?replace("world", "FreeMarker")}

In this example, use the replace function to replace “world” in “hello world” with “FreeMarker”.

2. numeric manipulation functions

FreeMarker provides many numerical manipulation functions that can be used to process and manipulate numerical values, for example:

• abs: Returns the absolute value of a number.
• round: rounds the value.
• floor: The value is rounded down.
• ceiling: Round up the value.

For example:

bashCopy code<#function tax price>
    <#return price * 0.08>
</#function>

${tax(1000)?round}

In this example, the round function is used to calculate the tax and round up the commodity price of 1000 yuan.

3. Date and time manipulation functions

FreeMarker provides many date and time manipulation functions that can be used to process and manipulate dates and times, for example:

• date: Formats a date and time as a string.
• time: Get the current time.
• number_to_date: Converts a number to a date.

For example:

luaCopy code<#assign date = "2023-04-27"?date("yyyy-MM-dd")>

${date?date("MMM d, yyyy")}

In this example, the string “2023-04-27” is converted to a date, and then the date function is used to format the date into a string in the format of “MMM d, yyyy”.

When using built-in functions, you need to pay attention to the following points:

• Built-in functions can be used to process and manipulate data, which can greatly simplify code writing and maintenance.
• The syntax and parameter lists of built-in functions can be found and studied in FreeMarker’s documentation.
• Built-in functions can also be used in the implementation of custom functions and macros to enhance their functionality and efficiency.

In short, FreeMarker’s macro and function built-in functions are an important part of using FreeMarker for template rendering. Only by mastering these built-in functions can better template rendering and data display be performed. When using built-in functions, you need to pay attention to the correctness of the grammar and the rationality of the way of use, all of which need to refer to the documentation and sample programs of FreeMarker.

Please explain FreeMarker’s macro and function custom function in detail

FreeMarker’s macro and function custom functions are an important part of using FreeMarker for template rendering, and can be used to define your own functions. Below we will introduce FreeMarker’s macro and function custom functions in detail:

1. function definition

In FreeMarker, you can use the <#function> tag to define a function. The syntax of the function definition is as follows:

javascriptCopy code<#function function_name(param1, param2, ...)>
    Function body
</#function>

Among them, function_name is the name of the custom function, and param1, param2, etc. are the parameter names of the function.

For example, define a function add that accepts two parameters a and b to realize the function of a+b:

lessCopy code<#function add(a, b)>
    <#return a + b>
</#function>

2. function call

In FreeMarker, you can use the ${} tag to call the function. The syntax of the function call is as follows:

scssCopy code${function_name(param1, param2, ...)}

Among them, function_name is the name of the custom function, and param1, param2, etc. are the parameter names of the function.

For example, calling the add function:

scssCopy code${add(1, 2)}

3. function return value

In FreeMarker, you can use the <#return> tag to specify the return value of the function. The syntax of the <#return> tag is as follows:

kotlinCopy code<#return expression>

where expression is the value to return.

For example, the return value of the function add is a+b, which can be specified using the <#return> tag:

lessCopy code<#function add(a, b)>
    <#return a + b>
</#function>

When using custom functions, you need to pay attention to the following points:

• Custom functions are usually used to process and manipulate data to achieve richer functions and logic.
• Custom functions can accept parameters of any type, including strings, numbers, dates, and more.
• Custom functions can be processed and operated using FreeMarker’s built-in functions to simplify code writing and maintenance.
• The use of custom functions requires attention to the type and quantity of parameters, as well as the type and format of return values.

In short, FreeMarker’s macro and function custom functions are an important part of using FreeMarker for template rendering. Only by mastering these basic syntaxes can better template rendering and data display be performed. When using custom functions, you need to pay attention to the correctness of the grammar and the rationality of the way of use, all of which need to refer to the documentation and sample programs of FreeMarker.

Please explain in detail FreeMarker’s data model Introduction to data model

FreeMarker’s data model refers to the data structure that the template depends on, including variables, collections, hash tables, objects, etc. These data can be passed in from the program or defined in the template. Below we will introduce the data model of FreeMarker in detail:

1. variable

Variables in FreeMarker can be basic data types such as numbers, strings, and Boolean values, or composite data types, such as collections, hash tables, objects, etc. When using variables in templates, you need to use ${} tags or #{} tags to reference, for example:

bashCopy code${name}

In this example, a variable named name is referenced.

2. gather

Collections in FreeMarker can be data structures such as arrays, lists, sets, etc., used to store a set of data of the same type, for example:

lessCopy code<#assign list = ["apple", "banana", "orange"]>

<#list list as item>
    ${item}
</#list>

In this example, define a list list containing three elements, use the <#list> tag to traverse the list, and output the value of each element.

3. hash table

Hash tables in FreeMarker can be used to store key-value pair data, for example:

arduinoCopy code<#assign map = {"name": "John", "age": 30}>

${map.name}

In this example, define a hash table map containing two key-value pairs, and use map.name to access the value corresponding to the name key.

4. object

Objects in FreeMarker can be JavaBean objects or custom Java objects for storing complex data structures, such as:

javaCopy code<#assign user = new com.example.User("John", 30)>

${user.name}

In this example, define a JavaBean object user that contains name and age attributes, and use user.name to access the value corresponding to the name attribute.

When using FreeMarker’s data model, you need to pay attention to the following points:

• The data model is the basis of template rendering, and it is necessary to ensure the correctness and integrity of the data.
• The data types and data structures of the data model need to match the needs of the template in order to render the template correctly.
• The data model can be dynamically generated in the program, or directly defined in the template, and the appropriate method can be selected according to the specific situation.

In short, the data model of FreeMarker is an important part of template rendering using FreeMarker. Only by mastering these basic grammars can template rendering and data display be performed better. When using the data model, you need to pay attention to the type, structure and integrity of the data, all of which need to refer to the FreeMarker documentation and sample programs.

Please explain the data model data type of FreeMarker in detail

FreeMarker’s data model contains a variety of data types, including basic data types, collection types, hash table types, and custom types. Below we will introduce the data types of FreeMarker in detail:

1. basic data type

FreeMarker supports common basic data types, including numbers, strings, Boolean values, dates and times, etc., for example:

• Number type: Can be integer, floating point, etc.
• String type: it can be general string, HTML string, XML string, etc.
• Boolean type: only two values, true and false.
• Date and time type: used to represent date and time, and can be formatted and calculated.

2. collection type

FreeMarker supports collection types, including lists, arrays, collections, etc., for storing a set of data of the same type, for example:

• List type: used to store a set of data, which can be traversed and processed using the <#list> tag.
• Array type: Similar to the list type, but it is a Java array type.
• Set type: used to store a set of unique data, which can perform operations such as intersection, union, and difference.

3. hash table type

FreeMarker supports the hash table type for storing key-value pair data, for example:

• Hash table type: used to store a set of key-value pair data, which can be traversed and processed using the <#list> tag.

4. custom type

FreeMarker supports custom types, including JavaBean objects, JavaMap objects, custom Java objects, etc., for example:

• JavaBean object: used to store a set of attributes, you can use the dot notation to access the attribute value.
• JavaMap object: used to store a set of key-value pair data, which can be traversed and processed using the <#list> tag.
• Custom Java objects: Custom Java objects can contain various properties and methods and can be used to store complex data structures.

When using FreeMarker data types, you need to pay attention to the following points:

• The choice of data type needs to be considered according to the characteristics and usage of the data in order to render the template correctly.
• Different data types can be operated and processed differently, and need to be selected and used according to needs.
• When using custom types, you need to ensure that the type and structure of the Java object matches the template’s requirements in order to render the template correctly.

In short, the data type of FreeMarker is an important part of template rendering using FreeMarker. Only by mastering these basic grammars can template rendering and data display be performed better. When using data types, you need to pay attention to the type, structure and integrity of the data, all of which need to refer to FreeMarker’s documentation and sample programs.

Please explain the data model example of FreeMarker in detail

Let’s give a specific example to illustrate how the FreeMarker data model is used.

Suppose we have a JavaBean object User, which contains three properties of name, age and address, we need to use the properties of this object in the template for rendering.

First, create a User object in the Java program and put it in the data model:

javaCopy codeUser user = new User("John", 30, "New York");
Map<String, Object> dataModel = new HashMap<>();
dataModel.put("user", user);

In the template, we can use the ${} tag to refer to the properties of the JavaBean object, for example:

cssCopy codeName: ${user.name}
Age: ${user.age}
Address: ${user.address}

In this way, when we pass the template and data model into the FreeMarker engine for rendering, the user’s information can be rendered correctly.

In addition to JavaBean objects, we can also use other types of data for rendering, such as:

javaCopy codeList<String> fruits = new ArrayList<>();
fruits.add("apple");
fruits.add("banana");
fruits.add("orange");

Map<String, Object> dataModel = new HashMap<>();
dataModel.put("fruits", fruits);

In the template, we can use the <#list> tag to traverse the data of the collection type, for example:

bashCopy code<#list fruits as fruit>
    ${fruit}
</#list>

In this way, when we pass the template and data model into the FreeMarker engine for rendering, the fruit list can be rendered correctly.

In actual use, we can choose the appropriate data type and data model for template rendering according to specific needs and data structures. It should be noted that the data type and data structure of the data model need to match the requirements of the template in order to render the template correctly.

Please explain FreeMarker and Java integration Java object access in detail

FreeMarker is a Java-based template engine, so it is very tightly integrated with Java, allowing easy access to Java objects and data. Below we will introduce the method of FreeMarker and Java integration in detail.

1. Configure the FreeMarker engine

First, you need to configure the FreeMarker engine in the Java program, including setting the path of the template folder, setting the encoding method of the template file, etc., for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

2. pass data into the template

In the Java program, we need to pass data into the FreeMarker engine for template rendering, for example:

javaCopy codeMap<String, Object> data = new HashMap<>();
data.put("name", "John");
data.put("age", 30);

Template temp = cfg.getTemplate("example.ftl");
Writer out = new OutputStreamWriter(System.out);
temp.process(data, out);

In this example, the data is stored in a Map object, which is passed to the FreeMarker engine for template rendering, and output to the standard output stream.

3. Access Java objects

In the template, we can use the ${} tag to access the properties and methods of the Java object, for example:

bashCopy codeName: ${user.name}
Age: ${user.getAge()}

In this example, access the name property and getAge() method of the JavaBean object user.

When accessing Java objects, you need to pay attention to the following points:

• Java objects must be accessible, that is, their properties and methods need to be public or protected access level.
• When accessing a Java object in a template, you need to use dot notation to access its properties and methods.
• FreeMarker supports access to various types of Java objects such as JavaBean objects, JavaMap objects, and custom Java objects.

In short, the integration of FreeMarker and Java is very tight, and Java objects and data can be accessed conveniently. It should be noted that when accessing a Java object, you need to ensure that its properties and methods are accessible, otherwise there will be access rights issues.

Please explain FreeMarker and Java integration Java method call in detail

After FreeMarker is integrated with Java, you can not only access the properties of Java objects, but also call the methods of Java objects to facilitate more complex operations. Below we will introduce the method of FreeMarker and Java integration in detail.

1. Configure the FreeMarker engine

First, you need to configure the FreeMarker engine in the Java program, including setting the path of the template folder, setting the encoding method of the template file, etc., for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

2. Pass the Java method into the template

In the Java program, we need to pass the Java method into the FreeMarker engine so that it can be called in the template, for example:

javaCopy codeclass MathUtil {
    public static int add(int a, int b) {
        return a + b;
    }
}

Map<String, Object> data = new HashMap<>();
data.put("math", new MathUtil());

Template temp = cfg.getTemplate("example.ftl");
Writer out = new OutputStreamWriter(System.out);
temp.process(data, out);

In this example, define a static method add() and put it in the data model so that it can be called in the template.

3. Call the Java method in the template

In the template, we can use the ${} tag to call the Java method, for example:

bashCopy codeResult: ${math.add(2, 3)}

In this example, the static method add() of the MathUtil class is called, and two parameters 2 and 3 are passed in, and the result 5 is output.

When calling Java methods, you need to pay attention to the following points:

• A Java method must be accessible, that is, its access level must be public or protected.
• FreeMarker supports calling static methods and instance methods of Java classes, which need to be selected according to specific situations.
• When calling a Java method in a template, you need to use dots and brackets to specify the name and parameters of the method, for example: object.methodName(arg1, arg2).

In short, the integration of FreeMarker and Java is very tight, and Java methods can be easily called for more complex operations. It should be noted that when calling a Java method, you need to ensure that the method is accessible, otherwise there will be access rights issues.

Please explain FreeMarker and Java integration JavaBeans integration in detail

After FreeMarker and Java are integrated, you can easily access and manipulate JavaBean objects for more complex operations. Below we will introduce in detail how FreeMarker and Java integrate JavaBeans.

1. Configure the FreeMarker engine

First, you need to configure the FreeMarker engine in the Java program, including setting the path of the template folder, setting the encoding method of the template file, etc., for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

2. Pass the JavaBean object into the template

In the Java program, we need to pass the JavaBean object into the FreeMarker engine so that it can be accessed in the template, for example:

javaCopy codeUser user = new User("John", 30);
Map<String, Object> data = new HashMap<>();
data.put("user", user);

Template temp = cfg.getTemplate("example.ftl");
Writer out = new OutputStreamWriter(System.out);
temp.process(data, out);

In this example, put the JavaBean object user into the data model for access in the template.

3. Access JavaBean objects in templates

In the template, we can use the ${} tag to access the properties of the JavaBean object, for example:

bashCopy codeName: ${user.name}
Age: ${user.age}

In this example, access the name attribute and age attribute of the JavaBean object user.

When accessing JavaBean objects, you need to pay attention to the following points:

• The JavaBean object must be accessible, that is, its properties need to have get methods and set methods.
• When accessing a JavaBean object in a template, you need to use a dot notation to access its properties, for example: object.propertyName.
• FreeMarker supports accessing properties and methods of JavaBean objects, and accessing nested properties and methods of JavaBean objects.

In short, the integration of FreeMarker and Java is very tight, and JavaBean objects can be easily accessed and manipulated for more complex operations. It should be noted that when accessing a JavaBean object, it is necessary to ensure that its properties and methods are accessible, otherwise there will be access rights issues.

Please explain in detail FreeMarker practical case website template generation

FreeMarker is a powerful template engine that can easily generate various types of templates. Let’s introduce a practical case, using FreeMarker to generate a website template.

1. Configure the FreeMarker engine

First, we need to configure the FreeMarker engine in the Java program, including setting the path of the template folder, setting the encoding method of the template file, etc., for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

2. Prepare the data model

Before generating the website template, we need to prepare the data model, including the website title, navigation bar, news list, etc. Store data in a Map object, for example:

javaCopy codeMap<String, Object> data = new HashMap<>();
data.put("title", "My Website");
data.put("nav", new String[] {"Home", "About", "News", "Contact"});
data.put("news", newsList);

In this example, put the website title, navigation bar, and news list into the data model.

3. Write template files

Next, we need to write template files for generating website templates. For example, you can write an index.ftl file with the following content:

htmlCopy code<!DOCTYPE html>
<html>
<head>
    <title>${title}</title>
</head>
<body>
    <nav>
        <ul>
            <#list nav as item>
                <li>${item}</li>
            </#list>
        </ul>
    </nav>

    <div id="news">
        <#list news as item>
            <div class="item">
                <h2>${item.title}</h2>
                <p>${item.content}</p>
            </div>
        </#list>
    </div>
</body>
</html>

In this example, the ${} tag is used to refer to the data in the data model to generate the navigation bar and news list of the website.

4. Generate site templates

Finally, pass the data model and template files into the FreeMarker engine to generate website templates, for example:

javaCopy codeTemplate temp = cfg.getTemplate("index.ftl");
Writer out = new FileWriter(new File("/path/to/output.html"));
temp.process(data, out);

In this example, the data model and template files are passed to the FreeMarker engine to generate a website template and output to the output.html file.

Through the above steps, we can use FreeMarker to generate website templates, including website title, navigation bar and news list, etc. In actual use, we can write appropriate template files and data models according to specific needs and data structures to generate different types of templates.

Please explain in detail the generation of FreeMarker practical case email templates

FreeMarker can easily generate various types of templates, including email templates. Let’s introduce a practical case, using FreeMarker to generate email templates.

1. Configure the FreeMarker engine

First, we need to configure the FreeMarker engine in the Java program, including setting the path of the template folder, setting the encoding method of the template file, etc., for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

2. Prepare the data model

Before generating the email template, we need to prepare the data model, including email subject, sender, recipient, email content, etc. Store data in a Map object, for example:

javaCopy codeMap<String, Object> data = new HashMap<>();
data.put("subject", "Welcome to My Website");
data.put("from", "sender@example.com");
data.put("to", "receiver@example.com");
data.put("content", "Dear ${name}, welcome to my website.");

In this example, put the email subject, sender, recipient, and email content into the data model.

3. Write template files

Next, we need to write template files for generating email templates. For example, you can write an email.ftl file with the following content:

htmlCopy code<html>
<head>
    <title>${subject}</title>
</head>
<body>
    <p>From: ${from}</p>
    <p>To: ${to}</p>
    <p>${content}</p>
</body>
</html>

In this example, the ${} tag is used to refer to the data in the data model to generate the sender, recipient and content of the email.

4. Generate email templates

Finally, pass the data model and template files into the FreeMarker engine to generate email templates, for example:

javaCopy codeTemplate temp = cfg.getTemplate("email.ftl");
Writer out = new StringWriter();
temp.process(data, out);

String emailContent = out.toString();

In this example, the data model and template files are passed to the FreeMarker engine to generate an email template and output it into a string.

Through the above steps, we can use FreeMarker to generate email templates, including email subject, sender, recipient and content. In actual use, we can write appropriate template files and data models according to specific needs and data structures to generate different types of templates. Finally, email templates can be used in application scenarios such as email sending.

Please explain in detail the PDF report generation of FreeMarker practical cases

FreeMarker can easily generate various types of templates, including PDF reports. Let’s introduce a practical case below, using FreeMarker to generate PDF reports.

1. Configure the FreeMarker engine

First, we need to configure the FreeMarker engine in the Java program, including setting the path of the template folder, setting the encoding method of the template file, etc., for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

2. Prepare the data model

Before generating PDF reports, we need to prepare the data model, including table headers, table data, etc. Store data in a Map object, for example:

javaCopy codeMap<String, Object> data = new HashMap<>();
data.put("title", "Sales Report");
data.put("header", new String[] {"Product Name", "Quantity", "Price", "Total Price"});
data.put("data", dataList);

In this example, the report title, table header, and table data are placed in the data model.

3. Write template files

Next, we need to write template files for generating PDF reports. You can use FreeMarker’s built-in PDF generation tools, for example:

htmlCopy code<html>
<head>
    <title>${title}</title>
</head>
<body>
    <table>
        <thead>
            <tr>
                <#list header as col>
                    <th>${col}</th>
                </#list>
            </tr>
        </thead>
        <tbody>
            <#list data as row>
                <tr>
                    <td>${row.name}</td>
                    <td>${row.quantity}</td>
                    <td>${row.price}</td>
                    <td>${row.total}</td>
                </tr>
            </#list>
        </tbody>
    </table>
</body>
</html>

In this example, the ${} tag is used to refer to the data in the data model to generate the header and table data of the PDF report.

4. Generate PDF report

Finally, pass the data model and template files into the FreeMarker engine, and use FreeMarker’s built-in PDF generation tools to generate PDF reports, for example:

javaCopy codeTemplate temp = cfg.getTemplate("report.ftl");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
Writer out = new OutputStreamWriter(baos);
temp.process(data, out);

PdfWriter writer = new PdfWriter(new FileOutputStream("output.pdf"));
PdfDocument pdf = new PdfDocument(writer);
ConverterProperties converterProperties = new ConverterProperties();
HtmlConverter.convertToPdf(new ByteArrayInputStream(baos.toByteArray()), pdf, converterProperties);

In this example, the data model and template files are passed into the FreeMarker engine and output into a byte array, and then the byte array is converted into a PDF file using FreeMarker’s built-in PDF generation tool class.

Through the above steps, we can use FreeMarker to generate PDF reports, including table headers and table data. In actual use, we can write appropriate template files and data models according to specific needs and data structures to generate different types of reports. Finally, reports can be used in application scenarios such as data statistics and analysis.

Please explain FreeMarker’s advanced topic custom commands in detail

FreeMarker provides many built-in instructions, such as if, list, etc., which can meet most template requirements. However, in some special cases, custom directives may be required to meet specific needs. Let’s introduce how to customize instructions in FreeMarker.

1. Implement the TemplateDirectiveModel interface

First, we need to implement the TemplateDirectiveModel interface, which contains the methods that custom directives need to implement, for example:

javaCopy codepublic class MyDirective implements TemplateDirectiveModel {

    @Override
    public void execute(Environment env, Map params, TemplateModel[] loopVars, TemplateDirectiveBody body) throws TemplateException, IOException {
        // TODO: 自定义指令的执行逻辑
    }
}

In this example, we implemented the TemplateDirectiveModel interface and customized a directive named MyDirective.

2. Register a custom directive

Next, we need to register the custom directive into the FreeMarker engine for use in the template. For example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

Map<String, TemplateDirectiveModel> directives = new HashMap<>();
directives.put("myDirective", new MyDirective());
cfg.setSharedVariable("directives", directives);

In this example, the custom instruction MyDirective is registered in the FreeMarker engine with the name myDirective.

3. Using custom directives in templates

Finally, use custom directives in your templates, for example:

htmlCopy code<@myDirective arg1="value1" arg2="value2">
    <!-- 自定义指令的内容 -->
</@myDirective>

In this example, the myDirective command is used and two parameters arg1 and arg2 are passed in. The specific content of the custom command can be written in the command body.

Through the above steps, we can customize instructions in FreeMarker to meet specific needs. Custom instructions can extend the functions of FreeMarker to provide more flexible and powerful template processing capabilities.

Please explain in detail the advanced topic configuration and tuning of FreeMarker

FreeMarker is a high-performance template engine, but in actual use, you may encounter some performance problems, which need to be configured and tuned. Let’s introduce the configuration and tuning of FreeMarker.

1. cache

FreeMarker provides a template cache function, which can cache the compiled template to avoid compiling every time it is used. You can set the template update interval through the setTemplateUpdateDelay method of the Configuration object, and set the cache policy through the setCacheStorage method, for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

cfg.setTemplateUpdateDelayMilliseconds(1000);
cfg.setCacheStorage(new SoftCacheStorage());

In this example, the template update interval is set to 1 second, and the cache policy is soft reference cache.

2. Enable JIT compilation

FreeMarker provides JIT (Just-In-Time) compilation function, which can compile templates into Java bytecodes to improve template execution speed. JIT compilation can be enabled through the setJitCompiler method of the Configuration object, for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

cfg.setJitCompiler(true);

In this example, JIT compilation is enabled.

3. custom class loader

FreeMarker needs to dynamically generate Java classes when compiling templates, and the default class loader may have some problems, such as inability to load classes, class duplication, etc. These problems can be solved by customizing the class loader, for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

ClassLoader cl = new CustomClassLoader();
cfg.setClassLoader(cl);

In this example, a class loader CustomClassLoader is customized and set as the class loader of the FreeMarker engine.

Through the above configuration and tuning, you can improve the performance and stability of FreeMarker, optimize the template processing efficiency, and improve the overall performance of the application. In actual use, reasonable configuration and tuning can be performed according to specific situations and needs.

Please explain FreeMarker’s advanced topic internationalization support in detail

FreeMarker provides internationalization (i18n) support, which can localize the text information in the template for use in different language environments. Let’s introduce FreeMarker’s internationalization support.

1. Prepare resource files

First of all, we need to prepare resource files, which contain text information in various language environments. Typically, resource files can be stored in the classpath, for example:

Copy codemessages.properties
messages_en.properties
messages_zh_CN.properties

In this example, the text information in the default language, English and Simplified Chinese are included.

2. Configure the FreeMarker engine

Next, we need to configure the FreeMarker engine in the Java program, including setting the path of the template folder, setting the encoding method of the template file, etc., for example:

javaCopy codeConfiguration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setDirectoryForTemplateLoading(new File("/path/to/templates"));
cfg.setDefaultEncoding("UTF-8");

cfg.setLocale(Locale.US);
cfg.setNumberFormat("0.##");

In this example, the default language is set to American English, and the number format is two decimal places.

3. Use internationalized text in templates

Finally, use internationalized text in your templates, for example:

htmlCopy code<h1>${msg("welcome")}</h1>
<p>${msg("hello", "John")}</p>

In this example, internationalized text is referenced using the msg function. In the default locale, the msg function will read the text information in messages.properties. If other locales are set, it will read the corresponding resource file.

4. Configuration resource file

If you need to add text information in other locales, you can add text information in the corresponding resource file, for example:

Copy codemessages_es.properties

In this example, the text information for the Spanish environment is added.

Through the above steps, we can implement internationalization support in FreeMarker and localize the text information in the template for use in different language environments. In actual use, you can add corresponding resource files and text information according to specific needs and language environments.

Please explain in detail FreeMarker resources and further study official documentation and tutorials

FreeMarker is a powerful and easy-to-use template engine that provides rich syntax and API to meet various template processing needs. If you want to learn FreeMarker in depth, you can refer to the following resources and further learning materials:

1. FreeMarker official documentation: FreeMarker provides complete official documentation, including basic syntax, advanced features, API, etc. The latest documentation can be downloaded from the official website ( https://freemarker.apache.org/) or browsed online.
2. FreeMarker sample code: FreeMarker provides some sample codes to help developers quickly get started and understand the usage and application scenarios of FreeMarker. The sample code can be downloaded from the official website ( https://freemarker.apache.org/examples.html).
3. FreeMarker online tools: FreeMarker provides online tools to edit and preview FreeMarker templates in the browser, which is convenient for developers to experiment and debug. You can visit the official website ( https://try.freemarker.apache.org/) to use the online tool.
4. FreeMarker Community: FreeMarker has an active community where developers can seek help, share experiences and exchange technologies. You can visit the official website ( https://freemarker.apache.org/community.html) for more community information.
5. FreeMarker tutorials and books: FreeMarker has many excellent tutorials and books, which can help developers learn and master the usage methods and skills of FreeMarker. For example, the book “FreeMarker Template Engine: Practical and Advanced” is a book that comprehensively introduces FreeMarker.

Through the above resources and learning materials, developers can learn FreeMarker in depth, master its usage methods and skills, and improve template processing efficiency and overall performance of applications.

Please explain in detail FreeMarker resources and further study Official Documentation and Tutorials Community and Q&A

FreeMarker has an active community and Q&A platform to help developers solve various problems and communicate technology. Let’s introduce FreeMarker’s community and Q&A platform.

1. FreeMarker Official Mailing List: The FreeMarker official mailing list is an open discussion group where developers can ask questions, answer questions, exchange experiences and share techniques. More information can be found on the official website ( https://freemarker.apache.org/mailing-lists.html).
2. Stack Overflow: Stack Overflow is a well-known question-and-answer platform, and there are also many questions and answers about FreeMarker. You can search for related questions on Stack Overflow ( https://stackoverflow.com/questions/tagged/freemarker).
3. Github Issues: The source code of FreeMarker is hosted on Github, and there are also related Issues discussion boards. Issues can be found and submitted in Github Issues ( https://github.com/apache/freemarker/issues).
4. FreeMarker Community: The FreeMarker Community is an active social network where developers can exchange technologies, share experiences and solve problems. More information can be found in the FreeMarker community ( https://gitter.im/freemarker/freemarker).

Through the above communities and question-and-answer platforms, developers can obtain rich technical resources and help, solve various problems and exchange technologies. In actual use, you can choose an appropriate platform and method to communicate and exchange according to the specific situation and needs.