java对象与json对象间的相互转换

1.简单的解析json字符串

首先将json字符串转换为json对象，然后再解析json对象，过程如下。

JSONObject jsonObject = JSONObject.fromObject(jsonStr);

 

  根据json中的键得到它的值

String name = jsonObject.getString("name");
int num = jsonObject.getInt("num");
String sex = jsonObject.getString("sex");
int age = jsonObject.getInt("age");

 

2.将json字符串转换为java对象

同样先将json字符串转换为json对象，再将json对象转换为java对象，如下所示。

JSONObject obj = new JSONObject().fromObject(jsonStr);//将json字符串转换为json对象

将json对象转换为java对象

Person jb = (Person)JSONObject.toBean(obj,Person.class);//将建json对象转换为Person对象

 

3.将java对象转换为json字符串

先将java对象转换为json对象，在将json对象转换为json字符串

JSONObject json = JSONObject.fromObject(obj);//将java对象转换为json对象

String str = json.toString();//将json对象转换为字符串

 

完整代码如下：

package baz.parse;

import java.util.ArrayList;
import java.util.List;

import net.sf.json.JSON;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import net.sf.json.JSONSerializer;
import baz.bean.Person;

public class ParseJson {

    private String jsonStr;

    public ParseJson() {

    }

    public ParseJson(String str){
        this.jsonStr = str;
    }
    /**
     * 解析json字符串
     */
    public void parse(){
        JSONObject jsonObject = JSONObject.fromObject(jsonStr);
        String name = jsonObject.getString("name");
        int num = jsonObject.getInt("num");
        String sex = jsonObject.getString("sex");
        int age = jsonObject.getInt("age");

        System.out.println(name + " " + num + " " + sex + " " + age);
    }
    //将json字符串转换为java对象
    public Person JSON2Object(){
        //接收{}对象，此处接收数组对象会有异常
        if(jsonStr.indexOf("[") != -1){
            jsonStr = jsonStr.replace("[", "");
        }
        if(jsonStr.indexOf("]") != -1){
            jsonStr = jsonStr.replace("]", "");
        }
        JSONObject obj = new JSONObject().fromObject(jsonStr);//将json字符串转换为json对象
        Person jb = (Person)JSONObject.toBean(obj,Person.class);//将建json对象转换为Person对象
        return jb;//返回一个Person对象
    }


}

package baz.bean;

public class Person {

    private String name;
    private int num;
    private String sex;
    private int age;

    public Person() {
        // TODO Auto-generated constructor stub
    }

    public Person(String name, int num, String sex, int age) {
        super();
        this.name = name;
        this.num = num;
        this.sex = sex;
        this.age = age;
    }



    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getNum() {
        return num;
    }

    public void setNum(int num) {
        this.num = num;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

}

 将java对象转换为json字符串

 

package baz.cons;


import net.sf.json.JSONObject;


/**
 * 将java对象转换为json字符串
 * @author Administrator
 *
 */
public class ConsJson {

    public ConsJson() {
        // TODO Auto-generated constructor stub
    }

    public String Object2Json(Object obj){
        JSONObject json = JSONObject.fromObject(obj);//将java对象转换为json对象
        String str = json.toString();//将json对象转换为字符串

        return str;
    }
}

测试类：

package baz.test;

import java.util.List;

import baz.bean.Person;
import baz.cons.ConsJson;
import baz.parse.ParseJson;


public class Test {
    public static void main(String[] args) {

        //将字符串转换为json对象，然后根据建得到相应的值
        ParseJson pj = new ParseJson("{\"name\":\"gu\",\"num\":123456,\"sex\":\"male\",\"age\":24}");
        pj.parse();

        //将一个json字符串转换为java对象
        Person p = pj.JSON2Object();
        System.out.println("Name:" + p.getName());
        System.out.println("Num:" + p.getNum());
        System.out.println("Sex:" + p.getSex());
        System.out.println("age:" + p.getAge());

        //将一个java对象转换为Json字符串
        Person p1 = new Person("gu1",123,"male",23);
        ConsJson cj = new ConsJson();
        String str1 = cj.Object2Json(p1);
        System.out.println(str1);

    }

}

测试输出如下：
gu 123456 male 24
Name:gu
Num:123456
Sex:male
age:24
{"age":23,"name":"gu1","num":123,"sex":"male"}