1.需求場景

資料報表大量實體類生成，模板化，降低維護難度。

2.專案環境

普通java專案 freemark

3.實現步驟

(1)匯入freemark jar包(使用版本FreeMarker_2.3.23)

(2)構建模板檔案，比如 entity層

entity.ftl

package ${entity.javaPackage};
 
/**
 * 
 * TODO ${entity.javaDoc}
 * @author admin
 *
 */
public class ${entity.className}
{
    /********** 屬性 ***********/
<#list entity.properties as property>
    private ${property.javaType} ${property.propertyName};//${property.propertyComment}
</#list>
    /********** get/set ***********/
<#list entity.properties as property>
    public ${property.javaType} get${property.propertyName?cap_first}() {
        return ${property.propertyName};
    }
 
    public void set${property.propertyName?cap_first}(${property.javaType} ${property.propertyName}) {
        this.${property.propertyName} = ${property.propertyName};
    }
</#list>
}
 

(3)生成java檔案幫助類

public class AutoUtil {
/***
 * 
* @Title: createEntity 
* @Description: TODO 建立實體類
* @param propertyList 欄位集合
* @param packageName 包全路徑名稱
* @param className 類名
* @param javaDoc 類註釋
* @param path  檔案生成路徑
 */
public static void createEntity(Configuration cfg, List<Property> propertyList,String packageName,
                                   String className,String javaDoc,String path){
	 Map<String, Object> root = new HashMap<String, Object>();
	 try{ 
	 Template template = cfg.getTemplate("entity.ftl");
     Entity user = new Entity();
     user.setJavaPackage(packageName); // 建立包名
     user.setClassName(className);  // 建立類名
     user.setJavaDoc(javaDoc);  // 類註釋
     // 將屬性集合新增到實體物件中
     user.setProperties(propertyList);
     // 建立.java類檔案
     File outDirFile = new File(path);
     if(!outDirFile.exists()){
         outDirFile.mkdir();
     }
     File javaFile = toJavaFilename(outDirFile, user.getJavaPackage(), user.getClassName());
     //資料
     root.put("entity", user);
     //寫檔案
     write2File(javaFile, template, root);
	}catch(Exception e){
		e.printStackTrace();
	}
}

/***
 * 
* @Title: write2File 
* @Description: TODO  將資料寫入檔案
* @param javaFile 檔案物件
* @param template  模板物件
* @param root 資料
 */
public static void write2File(File javaFile, Template template,Map<String,Object> root){
	try{
	Writer javaWriter = new FileWriter(javaFile);
    template.process(root, javaWriter);
    javaWriter.flush();
    System.out.println("檔案生成路徑：" + javaFile.getCanonicalPath());
    javaWriter.close();
    
    
    // 輸出到Console控制檯
    //Writer out = new OutputStreamWriter(System.out);
   // template.process(root, out);
   // out.flush();
   // out.close();
	}catch(Exception e){
		e.printStackTrace();
	}
}

/**
 * 建立.java檔案所在路徑 和 返回.java檔案File物件
 * @param outDirFile 生成檔案路徑
 * @param javaPackage java包名
 * @param javaClassName java類名
 * @return
 */
public static File toJavaFilename(File outDirFile, String javaPackage, String javaClassName) {
    String packageSubPath = javaPackage.replace('.', '/');
    File packagePath = new File(outDirFile, packageSubPath);
    File file = new File(packagePath, javaClassName + ".java");
    if(!packagePath.exists()){
        packagePath.mkdirs();
    }
    return file;
}

/**
 * 
* @Title: getTableProperty2Bean 
* @Description: TODO  生成 Bean
* @param field 欄位
* @param column 列名
* @return
 */
public static List<Property> getTableProperty2Bean(List<String> field,List<String> column){
	List<Property> propertyList = new ArrayList<Property>();
	for (int i = 0; i < field.size(); i++) {
		Property  p = new Property("String",field.get(i),column.get(i));
		propertyList.add(p);
	}
	return  propertyList;
}



/**
 * 
* @Title: array2List 
* @Description: TODO 陣列轉list
* @param array
 */
public static List<String> array2List(String array[]){
	List<String> list = new ArrayList<String>();
	for (int i = 0; i < array.length; i++) {
		list.add(array[i]);
	}
	return list;
}

}
 

(4)測試類

package com.dx.main;
public class Test {
	public static void main(String[] args) {
		Configuration cfg = new Configuration();
		try {
			// 載入模板路徑
			cfg.setDirectoryForTemplateLoading(new File("./template"));
			cfg.setObjectWrapper(new DefaultObjectWrapper());
			String path="專案絕對路徑";
		        
			String col ="日期，列名1，列名2";
			String fd="time,col1,col2";
			String field[]=fd.split(",");
			String column[] = col.split(",");
			List<String> fieldarr =AutoUtil.array2List(field); 
			List<String> columnarr =AutoUtil.array2List(column);
			//引數資訊
			String packageSuffix=".最後一級包名";
			String beanName="TestBean";
			String comment="註釋";
			String beanPackage="com.dx.bean"+packageSuffix;
			//生成java bean
			List<Property> propertyList = AutoUtil.getTableProperty2Bean(fieldarr, columnarr);
			//生成檔案
			AutoUtil.createEntity(cfg, propertyList,beanPackage, beanName, comment,path);
			 
		} catch (IOException e) {
			e.printStackTrace();
		}

	}
	
	
	
	 
}