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JSON-lib包对json的构造和方法的使用

程序员文章站 2022-05-08 08:47:40
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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:

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 stubDemo_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 stubDemo_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 stubMethodTest 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 stubdemo_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valueString value=jo.getString("extra");
        System.out.println(value);        //将字符串转化为JSONArrayJSONArray jsar=JSONArray.fromObject(value);
        String str_2=String.valueOf(jsar.get(1));
        System.out.println(str_2);        //将字符串转化为JSONObjectJSONObject 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 stubdemo_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}]}

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