Parse and construct a json string using JSONObject and JSONArray.

Parse and construct a json string using JSONObject and JSONArray.

The JSON-lib package (the two most critical classes are JSONObject and JSONArray) completes the construction of json and the use of some basic methods.

Differences:

① The string constructed by JSONObject is in key: value format. Multiple key-value pairs are connected by commas;

② The string constructed by JSONArray is in the array format ([array1, array2,...]).

Package download link to use: http://pan.baidu.com/s/1o7MZ8X8

1. Use of JSONObject.

(1) Two construction methods for JSON strings:

① Use a Java object; ② use a Map set.

Step 1: first create a Java project and import the dependency package;

Step 2: create two test classes:

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;    }                }

Step 3: Write the main method

Method 1:

Package com. snnu. json; import java. util. arrayList; import java. util. list; import net. sf. json. JSONObject; public class Demo_creajsonFromObject {// use a java Object to generate a json string public JSONObject createJsonFromObject (object 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 ("Zhang San"); t. setSex ("male"); t. setAge (21); Transport bike = new Transport ("bicycle", 267); Transport motorcycle = new Transport ("motorcycle", 3267 ); transport car = new Transport ("car", 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 );}}

The generated json string is:

{"Age": 21, "myTool": [{"name": "bicycle", "price": 267 },{ "name": "motorcycle ", "price": 3267 },{ "name": "car", "price": 100000}], "name": "Zhang San", "sex": "male "}

 

Method 2:

Package com. snnu. json; import java. util. hashMap; import java. util. map; import net. sf. json. JSONObject; public class Demo_creajsonFromMap {// use the map set to generate the json String 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", "Zhang San"); mmap. put ("sex", "male"); mmap. put ("age", "21"); JSONObject ob = demo. createJsonFromMap (mmap); System. out. println (ob );}}

The generated json string is:

{"Sex": "male", "name": "Zhang San", "age": "21 "}

(2) Examples of three common JSONObject methods.

Package com. snnu. json; import java. util. arrayList; import java. util. list; import net. sf. json. JSONObject; public class MethodTest {// put method: Insert a node into a json file. If the node already exists, the value of the node will be replaced with 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 method: you can accumulate values under the same key. If the value corresponding to the key has a value, it is accumulated in the form of an array; otherwise, it is equivalent to the put method 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 ;} // basically consistent with the put method 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 ("Use the put Method of JSONObject" + test. testPut (); System. out. println ("Use the accumulate method of JSONObject" + test. testAccumulate (); System. out. println ("use the element method of JSONObject" + test. testElement ());}}

 

① The format of the json string output by the put method is as follows:

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

② The result of formatting the json string output by the accumulate method is:

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

③ The format result of the json string output by the element method is:

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

Ii. Use of JSONArray

(1) Basic usage:

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 ("use of JSONArray:" + djs. testJsonArray ());}}

Format the output string:

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

Iii. Integrated instances

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", "Zhang San"); 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); // obtain the corresponding value String value = jo based on the key value (extra. getString ("extra"); System. out. println (value); // converts a string to JSONArray jsar = JSONArray. fromObject (value); String str_2 = String. valueOf (jsar. get (1); System. out. println (str_2); // converts a string to JSONObject jsob = JSONObject. fromObject (str_2); System. out. println ("name:" + jsob. getString ("name"); System. out. println ("Price:" + jsob. getString ("price"); System. out. println ("-----------------------------------------------------------------------------"); return jo;} public static void main (String [] args) {// TODO Auto-generated method stub demo_testJson dtj = new demo_testJson (); System. out. println ("Comprehensive test:" + dtj. test ());}}

Output result:

{"Name": "Zhang San", "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} name: car price: 10000 --------------------------------------------------------------------------- Comprehensive Test: {"name": "Zhang San", "sex": "f", "age": 21, "extra ": [{"name": "bike", "price": 250 },{ "name": "car", "price": 10000 },{ "name ": "motor", "price": 3000}]}