把list对象转换成json字符串

在javaweb中，有时候需要返回json数据到前端页面，这里列举一个把list数据格式转换成json数据格式的util类，可以把此类放在项目的util工具包下使用。

package com.pifeng.util;

import java.lang.reflect.Field;

import java.util.List;

/**

* @author pifeng 把list转换成json格式

* @param <T>

* @Date 2015-4-10

*/

public class ListToJson<T> {

public String listToJson(List<T> list) {

// 变量

StringBuffer jsonStr = new StringBuffer();

// 前提条件

if (null == list || 0 == list.size()) {

return null;

}

// class对象

Class<?> classType = list.get(0).getClass();

// 得到javabean的名字

String javaBeanClassName = classType.getSimpleName();

jsonStr.append("{\"").append(javaBeanClassName.toLowerCase()).append("s").append("\":[");

// 此JavaBean中所声明的所有字段

Field[] fields = classType.getDeclaredFields();

for (int i = 0; i < list.size(); i++) {

jsonStr.append("{");

for (Field field : fields) {

// 得到字段名

String fieldName = field.getName();

field.setAccessible(true);

// 得到指定对象上此 Field 表示的字段的值

Object fieldValue;

try {

fieldValue = field.get(list.get(i));

jsonStr.append("\"").append(fieldName.toLowerCase()).append("\":").append("\"").append(fieldValue).append("\"").append(",");

} catch (IllegalArgumentException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}

}

jsonStr.deleteCharAt(jsonStr.length() - 1);

jsonStr.append("},");

}

jsonStr.deleteCharAt(jsonStr.length() - 1);

jsonStr.append("]}");

return jsonStr.toString();

}

}

测试类：

package test;

import java.util.*;

import com.pifeng.entity.Student;

import com.pifeng.util.ListToJson;

public class TestListToJson {

/**

* @param args

*/

public static void main(String[] args) {

// 创建一个list 测试学生

List<Student> list = new ArrayList<Student>();

list.add(new Student(1, "张三", 20, true, new Date()));

list.add(new Student(2, "李四", 20, true, new Date()));

list.add(new Student(3, "王五", 20, false, new Date()));

list.add(new Student(4, "赵六", 20, true, new Date()));

list.add(new Student(5, null, 20, true, new Date()));

String json = new ListToJson<Student>().listToJson(list);

System.out.println(json);

}

}

测试结果：{"students":[{"age":"20","birthday":"Mon Dec 28 22:23:50 CST 2015","id":"1","name":"张三","sex":"true"},{"age":"20","birthday":"Mon Dec 28 22:23:50 CST 2015","id":"2","name":"李四","sex":"true"},{"age":"20","birthday":"Mon Dec 28 22:23:50 CST 2015","id":"3","name":"王五","sex":"false"},{"age":"20","birthday":"Mon
Dec 28 22:23:50 CST 2015","id":"4","name":"赵六","sex":"true"},{"age":"20","birthday":"Mon Dec 28 22:23:50 CST 2015","id":"5","name":"null","sex":"true"}]}