定义一个JavaBean类Person:

package ccc.json;

public class Person {

    Integer id;

    String name;

    String place;

    public Person(Integer id, String name, String place) {

        super();

        this.id = id;

        this.name = name;

        this.place = place;

    }

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getPlace() {

        return place;

    }

    public void setPlace(String place) {

        this.place = place;

    }

    @Override

    public String toString() {

        return "Person [id=" + id + ", name=" + name + ", place=" + place + "]";

    }

}

再定义一个JsonService.

用于生成各种形式的对象如Object,List,List<Map<String,Object>> :

package ccc.json;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

public class JsonService {

    public Person getPerson(){

        Person person=new Person(123,"bobo","HangZhou");

        return person;

    }

    public List<Person> getPersonList(){

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

        Person person1 = new Person(123,"sisi","BeiJing");

        Person person2 = new Person(2002, "bobo", "HangZhou");

        list.add(person1);

        list.add(person2);

        return list;

    }

    public List<String> getList(){

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

        list.add("BeiJing");

        list.add("HangZhou");

        return list;

    }

    public Map<String,Object> getMap(){

        Map<String,Object> map=new HashMap<String, Object>();

        map.put("id", 123);

        map.put("name","sisi");

        map.put("place", "BeiJing");

        return map;

    }

    public List<Map<String,Object>> getlistMap(){

        List<Map<String,Object>> list=new ArrayList<Map<String,Object>>();

        Map<String,Object> map1=new HashMap<String, Object>();

        map1.put("id", 123);

        map1.put("name","sisi");

        map1.put("place", "BeiJing");

        Map<String,Object> map2=new HashMap<String, Object>();

        map2.put("id", 456);

        map2.put("name","bobo");

        map2.put("place", "HangZhou");

        list.add(map1);

        list.add(map2);

        return list;

    }

}

GsonDemo入口:

package ccc.json;

import java.util.List;

import java.util.Map;

import com.google.gson.Gson;

import com.google.gson.reflect.TypeToken;

public class Json_demo {

    public static void main(String[] args) {

        Gson gson = new Gson();

        JsonService service = new JsonService();

        String str1 = gson.toJson(service.getPerson());

        System.out.println("1: "+str1);

//        1: {"id":123,"name":"bobo","place":"HangZhou"}

        String str4 = gson.toJson(service.getMap());

        System.out.println("2: "+str4);

//        2: {"id":123,"name":"sisi","place":"BeiJing"}

        String str2 = gson.toJson(service.getPersonList());

        System.out.println("3: "+str2);

//        3: [{"id":123,"name":"sisi","place":"BeiJing"},{"id":2002,"name":"bobo","place":"HangZhou"}]

        String str3 = gson.toJson(service.getList());

        System.out.println("4: "+str3);

//        4: ["BeiJing","HangZhou"]

        String str5 = gson.toJson(service.getlistMap());

        System.out.println("5: "+str5);

//        5: [{"id":123,"name":"sisi","place":"BeiJing"},{"id":456,"name":"bobo","place":"HangZhou"}]

        Person  personA = gson.fromJson(str4, Person.class);

        System.out.println(personA);

//        Person [id=123, name=sisi, place=BeiJing]

        Map<String,Object> mapA = gson.fromJson(str4, Map.class);

        System.out.println(mapA);

//        {id=123.0, name=sisi, place=BeiJing}

        //在已经知道要转成List的情况下可以直接带List.class参数

        List<Map> list = gson.fromJson(str5 /*str2*/, List.class);

        for(Map map : list){

            String s = gson.toJson(map);

            Person p =gson.fromJson(s, Person.class);

            System.out.println(p);

        }

//        Person [id=123, name=sisi, place=BeiJing]

//        Person [id=456, name=bobo, place=HangZhou]

        //转泛型的时候会把int转成double

        List<Map<String,Object>> list_map = gson.fromJson(str5, new TypeToken<List<Map<String,Object>>>(){}.getType());

        for(Map m: list_map){

            System.out.println(m);

        }

//        {id=123.0, name=sisi, place=BeiJing}

//        {id=456.0, name=bobo, place=HangZhou}

        //转Person可以把double的小数舍去

        List<Person> personList = gson.fromJson(str2 /*str5*/, new TypeToken<List<Person>>(){}.getType());

        for(Person p: personList){

            System.out.println(p);

        }

//        Person [id=123, name=sisi, place=BeiJing]

//        Person [id=2002, name=bobo, place=HangZhou]

    }

}

gson格式化-美化

Gson gson = new GsonBuilder().setPrettyPrinting().create();

String gsonInfo = gson.toJson(map);

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