JSONObject和JSONArray解析和构造json字符串

Posted 2020-09-25 兰公子

JSON-lib包（最关键的两个类分别是JSONObject和JSONArray）完成对json的构造和一些基本方法的使用。

二者区别：

        ①JSONObject构造的字符串是键值对形式（key:value），多个键值对间以英文逗号连接；

        ②JSONArray构造的字符串是数组形式（[array1,array2,...]）。

需要使用的包下载链接：http://pan.baidu.com/s/1o7MZ8X8 

一、JSONObject的使用。

（1）JSON字符串的两种构造方法：

①使用Java对象；②使用Map集合。

步骤一：首先新建Java工程，导入依赖包；

步骤二：建立两个测试类：

Teacher.java

package com.snnu.json;

import java.util.List;

public class Teacher {
    private String name;
    private String sex;
    private int age;

    private List<Transport> myTool;
    
    
    public Teacher(){
        
    }
    
    public Teacher(String name,String sex,int age,List<Transport> myTool){
        this.name = name;
        this.sex = sex;
        this.age = age;
        this.myTool = myTool;
    }

    public String getName() {
        return name;
    }

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

    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;
    }

    public List<Transport> getMyTool() {
        return myTool;
    }

    public void setMyTool(List<Transport> myTool) {
        this.myTool = myTool;
    }

}

Transport.java

package com.snnu.json;

public class Transport {
    
    private String name;
    private float price;
    
    public Transport(){
        
    }
    
    public Transport(String name,float price){
        this.name = name;
        this.price = price;
    }
    
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public float getPrice() {
        return price;
    }
    public void setPrice(float price) {
        this.price = price;
    }
    
    
    
    
}

步骤三：写main方法

       方式一：

package com.snnu.json;

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

import net.sf.json.JSONObject;

public class Demo_creajsonFromObject {

    // 利用java对象生成json字符串
    public JSONObject createJsonFromObject(Object object) {
        return JSONObject.fromObject(object);
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Demo_creajsonFromObject demo = new Demo_creajsonFromObject();

        Teacher t = new Teacher();
        t.setName("张三");
        t.setSex("男");
        t.setAge(21);

        Transport bike = new Transport("自行车", 267);
        Transport motorcycle = new Transport("摩托车", 3267);
        Transport car = new Transport("小汽车", 100000);
        List<Transport> tools = new ArrayList<Transport>();
        tools.add(bike);
        tools.add(motorcycle);
        tools.add(car);

        t.setMyTool(tools);

        JSONObject ob = demo.createJsonFromObject(t);

        System.out.println(ob);

    }

}

       生成的json字符串为：

{
    "age": 21,
    "myTool": [
        {
            "name": "自行车",
            "price": 267
        },
        {
            "name": "摩托车",
            "price": 3267
        },
        {
            "name": "小汽车",
            "price": 100000
        }
    ],
    "name": "张三",
    "sex": "男"
}

   

 

 方式二：

package com.snnu.json;

import java.util.HashMap;
import java.util.Map;

import net.sf.json.JSONObject;

public class Demo_creajsonFromMap {

    //使用map集合生成json字符串
    public JSONObject createJsonFromMap(Map<String,String> map){
        JSONObject jsob=new JSONObject();
        jsob.putAll(map);
        return jsob;
    }
    
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Demo_creajsonFromMap demo=new Demo_creajsonFromMap();
        
        Map<String,String> mmap=new HashMap<String,String>();
        mmap.put("name", "张三");
        mmap.put("sex", "男");
        mmap.put("age", "21");
        
        JSONObject ob=demo.createJsonFromMap(mmap);
        System.out.println(ob);
        
    }

}

生成的json字符串为：

{
    "sex": "男",
    "name": "张三",
    "age": "21"
}

（2）JSONObject的三个常用方法举例。

package com.snnu.json;

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

import net.sf.json.JSONObject;

public class MethodTest {

    //put方法：在一个json中插入一个节点，若该节点已存在，则该节点的值将会被替换
    public JSONObject testPut(){
        JSONObject jo1=new JSONObject();
        
        jo1.put("a", "1");
        jo1.put("b", "2");
        jo1.put("c", "3");
        
        Transport bike=new Transport("bike",200);
        jo1.put("d", bike);
        
        List<String> list=new ArrayList<String>();
        list.add("one");
        list.add("two");
        list.add("three");
        jo1.put("e", list);
        
        jo1.put("a", "100");
        
        return jo1;
    }
    
    
    //accumulate方法:可以在同一个key下累积值，若key对应的value有值，则以数组形式累积；否则相当于put方法
    public JSONObject testAccumulate(){
        JSONObject jo2=new JSONObject();
        
        jo2.put("a", "1");
        jo2.put("b", "2");
        jo2.put("c", "3");
        jo2.accumulate("c", "300");
        
        Transport bike=new Transport("bike",200);
        jo2.accumulate("c", bike);
        
        List<String> list=new ArrayList<String>();
        list.add("one");
        list.add("two");
        list.add("three");
        jo2.accumulate("c", list);
        
        jo2.put("d", "4");
        
        return jo2;
    }
    
    
    //与put方法基本一致
    public JSONObject testElement(){
        JSONObject jo3=new JSONObject();
        
        jo3.put("a", "1");
        jo3.put("b", "2");
        jo3.put("c", "3");
        jo3.element("c", "300");
        
        
        return jo3;
    }
    
    
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        MethodTest test=new MethodTest();
        System.out.println("JSONObject的put方法使用"+test.testPut());
        System.out.println("JSONObject的accumulate方法使用"+test.testAccumulate());
        System.out.println("JSONObject的element方法使用"+test.testElement());
        
    }

}

 

    ①put方法输出json字符串格式化结果为：

{
    "a": "100",
    "b": "2",
    "c": "3",
    "d": {
        "name": "bike",
        "price": 200
    },
    "e": [
        "one",
        "two",
        "three"
    ]
}

    ②accumulate方法输出json字符串格式化结果为：

{
    "a": "1",
    "b": "2",
    "c": [
        "3",
        "300",
        {
            "name": "bike",
            "price": 200
        },
        [
            "one",
            "two",
            "three"
        ]
    ],
    "d": "4"
}

    ③element方法输出json字符串格式化结果为：

{
    "a": "1",
    "b": "2",
    "c": "300"
}

 二、JSONArray的使用

（1）基本使用：

package com.snnu.json;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class demo_JsonArray {
    
    
    public JSONObject testJsonArray(){
        JSONObject ob=new JSONObject();
        
        JSONArray ja=new JSONArray();
        ja.add("1");
        ja.add("2");
        ja.add("3");
        ja.add("4");
        ja.add("5");
        
        ob.put("array", ja);
        
        return ob;
    }
    
    

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        demo_JsonArray djs=new demo_JsonArray();
        System.out.println("JSONArray的使用："+djs.testJsonArray());
        
    }

}

对输出后的字符串进行格式化：

{
    "array": [
        "1",
        "2",
        "3",
        "4",
        "5"
    ]
}

三、综合实例

package com.snnu.json;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class demo_testJson {
    
    
    
    public JSONObject test(){
        
        JSONObject jo=new JSONObject();
        jo.put("name", "张三");
        jo.put("sex","f");
        jo.put("age",21);
        
        Transport bike=new Transport("bike",250);
        jo.put("extra", bike);
        Transport car=new Transport("car",10000);
        jo.accumulate("extra", car);
        Transport motor=new Transport("motor",3000);
        jo.accumulate("extra", motor);
        
        System.out.println(jo);
        
        //根据key值（为extra）取对应的value
        String value=jo.getString("extra");
        System.out.println(value);
        
        //将字符串转化为JSONArray
        JSONArray jsar=JSONArray.fromObject(value);
        String str_2=String.valueOf(jsar.get(1));
        System.out.println(str_2);
        
        //将字符串转化为JSONObject
        JSONObject jsob=JSONObject.fromObject(str_2);
        System.out.println("名称："+jsob.getString("name"));
        System.out.println("价钱："+jsob.getString("price"));
        
        System.out.println("-------------------------------分界线-------------------------------------------");
        
        return jo;
        
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        demo_testJson dtj=new demo_testJson();
        System.out.println("综合测试："+dtj.test());
    }

}

输出结果为：

{"name":"张三","sex":"f","age":21,"extra":[{"name":"bike","price":250},{"name":"car","price":10000},{"name":"motor","price":3000}]}
[{"name":"bike","price":250},{"name":"car","price":10000},{"name":"motor","price":3000}]
{"name":"car","price":10000}
名称：car
价钱：10000
-------------------------------分界线-------------------------------------------
综合测试：{"name":"张三","sex":"f","age":21,"extra":[{"name":"bike","price":250},{"name":"car","price":10000},{"name":"motor","price":3000}]}