freemaker根据模板生成Java代码（代码生成器原理）

拼搏现实的明天。 2023-02-17 06:24 40阅读 0赞

freemaker这个jar包可以更加有提前编辑好的模板生成Java代码，做到“不写重复代码”。  
实现的步骤如下：  
第一步：springboot的pom.xml文件加入依赖包

<dependency>
                <groupId>org.freemarker</groupId>
                <artifactId>freemarker</artifactId>
                <version>2.3.23</version>
            </dependency>

第二步：编写模板

package ${ classPath};
    
    public class ${ className} { 
    
    private Integer ${ Id};
    private String ${ userName};
    private String ${ password};
    
    
    public Integer get${ Id}(){ 
    return ${ Id};
    }
    
    public void set${ Id}(Integer ${ Id}){ 
    
    this.${ Id}=${ Id};
    }
    
    public String get${ userName}(){ 
    return ${ userName};
    }
    
    public void set${ userName}(String ${ userName}){ 
    this.${ userName}=${ userName};
    
    }
    
    public String get${ password}(){ 
    return ${ password};
    }
    
    public void set${ password}(String ${ password}){ 
    this.${ password}=${ password};
    }
    
    }

第三步：编写生成代码的类

import java.io.BufferedWriter;
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.OutputStreamWriter;
    import java.io.Writer;
    import java.util.HashMap;
    import java.util.Map;
    
    import freemarker.template.Configuration;
    import freemarker.template.Template;
    
    
    public class FreemarkerDemo { 
    
        private static final String TEMPLATE_PATH = "src/main/java/com/chen/www/chendemo/CodeGenerator";
        private static final String CLASS_PATH = "src/main/java/com/chen/www/chendemo/CodeGenerator";
    
        public static void main(String[] args) { 
            // step1 创建freeMarker配置实例
            Configuration configuration = new Configuration();
            Writer out = null;
            try { 
                // step2 获取模版路径
                configuration.setDirectoryForTemplateLoading(new File(TEMPLATE_PATH));
                // step3 创建数据模型
                Map<String, Object> dataMap = new HashMap<String, Object>();
                dataMap.put("classPath", "com.chen.www.chendemo");
                dataMap.put("className", "User");
                dataMap.put("Id", "Id");
                dataMap.put("userName", "userName");
                dataMap.put("password","password");
                // step4 加载模版文件
                Template template = configuration.getTemplate("test.ftl");
                // step5 生成数据
                File docFile = new File(CLASS_PATH + "\\" + "User.java");
                out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(docFile)));
                // step6 输出文件
                template.process(dataMap, out);
                System.out.println("文件创建成功 !");
            } catch (Exception e) { 
                e.printStackTrace();
            } finally { 
                try { 
                    if (null != out) { 
                        out.flush();
                    }
                } catch (Exception e2) { 
                    e2.printStackTrace();
                }
            }
        }
    
    }

文件目录如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1bnl1aHVhX2tleWJvYXJk_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1bnl1aHVhX2tleWJvYXJk_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200613002246473.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1bnl1aHVhX2tleWJvYXJk,size_16,color_FFFFFF,t_70