Java模板引擎生成代码的几种常见方式及其使用方法

<dependency>
    <groupId>org.freemarker</groupId>
    <artifactId>freemarker</artifactId>
    <version>2.3.32</version>
</dependency>

import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;

import java.io.*;
import java.util.HashMap;
import java.util.Map;

public class FreeMarkerCodeGenerator {
    public static void main(String[] args) throws IOException, TemplateException {
        // 创建配置实例
        Configuration cfg = new Configuration(Configuration.VERSION_2_3_32);
        
        // 设置模板文件目录
        cfg.setDirectoryForTemplateLoading(new File("src/main/resources/templates"));
        
        // 设置默认编码
        cfg.setDefaultEncoding("UTF-8");
        
        // 获取模板
        Template template = cfg.getTemplate("code-template.ftl");
        
        // 准备数据模型
        Map<String, Object> dataModel = new HashMap<>();
        dataModel.put("className", "User");
        dataModel.put("packageName", "com.example.model");
        dataModel.put("fields", new String[]{"id", "name", "email"});
        
        // 输出文件
        Writer fileWriter = new FileWriter(new File("User.java"));
        template.process(dataModel, fileWriter);
        fileWriter.close();
        
        System.out.println("代码生成完成！");
    }
}

package ${packageName};

public class ${className} {
<#list fields as field>
    private String ${field};
</#list>

<#list fields as field>
    public String get${field?cap_first}() {
        return ${field};
    }

    public void set${field?cap_first}(String ${field}) {
        this.${field} = ${field};
    }
</#list>
}

<dependency>
    <groupId>org.apache.velocity</groupId>
    <artifactId>velocity-engine-core</artifactId>
    <version>2.3</version>
</dependency>

import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.runtime.RuntimeServices;
import org.apache.velocity.runtime.RuntimeSingleton;
import org.apache.velocity.runtime.parser.ParseException;
import org.apache.velocity.runtime.parser.node.SimpleNode;

import java.io.*;
import java.util.Properties;

public class VelocityCodeGenerator {
    public static void main(String[] args) throws IOException, ParseException {
        // 初始化Velocity引擎
        Properties props = new Properties();
        props.setProperty("resource.loader", "file");
        props.setProperty("file.resource.loader.class", 
            "org.apache.velocity.runtime.resource.loader.FileResourceLoader");
        props.setProperty("file.resource.loader.path", "src/main/resources/templates");
        
        VelocityEngine ve = new VelocityEngine(props);
        ve.init();
        
        // 获取模板
        Template template = ve.getTemplate("velocity-template.vm");
        
        // 创建上下文并添加数据
        VelocityContext context = new VelocityContext();
        context.put("className", "Product");
        context.put("packageName", "com.example.model");
        String[] fields = {"id", "name", "price"};
        context.put("fields", fields);
        
        // 输出生成的代码
        Writer writer = new FileWriter("Product.java");
        template.merge(context, writer);
        writer.close();
        
        System.out.println("Velocity代码生成完成！");
    }
}

package $packageName;

public class $className {
#foreach($field in $fields)
    private String $field;
#end

#foreach($field in $fields)
    public String get${field.substring(0,1).toUpperCase()}${field.substring(1)}() {
        return $field;
    }

    public void set${field.substring(0,1).toUpperCase()}${field.substring(1)}(String $field) {
        this.$field = $field;
    }
#end
}

<dependency>
    <groupId>org.thymeleaf</groupId>
    <artifactId>thymeleaf</artifactId>
    <version>3.1.2.RELEASE</version>
</dependency>

import org.thymeleaf.TemplateEngine;
import org.thymeleaf.context.Context;
import org.thymeleaf.templateresolver.FileTemplateResolver;

import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class ThymeleafCodeGenerator {
    public static void main(String[] args) throws IOException {
        // 配置模板引擎
        TemplateEngine templateEngine = new TemplateEngine();
        FileTemplateResolver templateResolver = new FileTemplateResolver();
        templateResolver.setPrefix("src/main/resources/templates/");
        templateResolver.setSuffix(".html");
        templateResolver.setTemplateMode("TEXT");
        templateResolver.setCharacterEncoding("UTF-8");
        templateEngine.setTemplateResolver(templateResolver);
        
        // 创建上下文
        Context context = new Context();
        context.setVariable("className", "Order");
        context.setVariable("packageName", "com.example.model");
        context.setVariable("fields", Arrays.asList("id", "customerName", "totalAmount"));
        
        // 处理模板
        String result = templateEngine.process("thymeleaf-template", context);
        
        // 写入文件
        Writer writer = new FileWriter("Order.java");
        writer.write(result);
        writer.close();
        
        System.out.println("Thymeleaf代码生成完成！");
    }
}

package [( ${packageName} )];

public class [( ${className} )] {
[# th:each="field : ${fields}"]
    private String [( ${field} )];[/]

[# th:each="field : ${fields}"]
    public String get[( ${#strings.capitalize(field)} )]() {
        return [( ${field} )];
    }

    public void set[( ${#strings.capitalize(field)} )](String [( ${field} )]) {
        this.[( ${field} )] = [( ${field} )];
    }
[/]
}