Java gson使用 将Java对象转为Json 并 Json转回Java对象

简述：

testJson_1中 将不同的java对象转换为json格式文件（String),

testJson_2中传入testJson_1中生成的JSON String 参数，反向返回各种Java的对象

包括：java的String、List、HashMap、JavaBean, 以及对象内包含list成员的对象转为Json String 并且 Json转回

注意点：

Gson的toJson() ,fromJson()函数使用，和两个函数所要求的参数

使用gson 1.7.1包（导入方法是用ivy工具-可参考配置里的一篇记录，或者直接加入装jar包）



代码:

1) Java Object To JSON



TestJson_1.java

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package testJson;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import com.google.gson.*;

class PersonInfo{

PersonInfo(String name,int age){

this.name = name;

this.age = age;

}

public PersonInfo() {

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

private String name;

private int age;

}

class FriendsBook{

FriendsBook(String ownerName,List<PersonInfo> friendsBook){

this.ownerName = ownerName;

this.friendsBook = friendsBook;

}

public String getOwnerName() {

return ownerName;

}

public void setOwnerName(String ownerName) {

this.ownerName = ownerName;

}

public List<PersonInfo> getFriendsBook() {

return friendsBook;

}

public void setFriendsBook(List<PersonInfo> friendsBook) {

this.friendsBook = friendsBook;

}

private String ownerName;

private List<PersonInfo> friendsBook;

}

//define a PersonBean to test Bean to Json

class PersonBean{

PersonBean(int id,String name,int age){

setId(id);

setName(name);

setAge(age);

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

private int id;

private String name;

private int age;

private ArrayList<String>friendsList;

}

/**

*

* Java Object TO JSON String

*

*/

public class TestJson_1 {

//use Gson lib

private static Gson gson = new Gson();

public String GetStringToJson(){

String jsonResult = gson.toJson(new String("aaa"));

return jsonResult;

}

public String GetArrayListToJson(){

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

list.add("aaa");

list.add("bbb");

list.add("ccc");

String jsonResult = gson.toJson(list);

return jsonResult;

}

public String GetHashMapToJson(){

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

map.put(1, "aaa");

map.put(2, "bbb");

map.put(3, "ccc");

String jsonResult = gson.toJson(map);

return jsonResult;

}

public String GetPersonBeanToJson(){

PersonBean pbean = new PersonBean(0,"aaa",21);

String jsonResult = gson.toJson(pbean);

return jsonResult;

}

public String GetFriendsBookToJson(){

PersonInfo p0 = new PersonInfo("John",22);

PersonInfo p1 = new PersonInfo("Marry",24);

PersonInfo p2 = new PersonInfo("Hellon",21);

List<PersonInfo> friendsList = new ArrayList<PersonInfo>();

friendsList.add(p0);

friendsList.add(p1);

friendsList.add(p2);

FriendsBook friendsBook = new FriendsBook("OWNER",friendsList);

String jsonResult = gson.toJson(friendsBook);

return jsonResult;

}

}

2) JSON To Java Object

TestJson_2.java

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package testJson;

import java.lang.reflect.Type;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.Map;

import com.google.gson.Gson;

import com.google.gson.reflect.TypeToken;

//JSON String To Java Object

public class TestJson_2 {

private static Gson gson = new Gson();

public String GetJsonToString(String jsonString){

String str = gson.fromJson(jsonString, String.class);

return str;

}

public ArrayList<String> GetJsonToArrayList(String jsonString){

ArrayList<String> list =

gson.fromJson(jsonString, new TypeToken<ArrayList<String>>(){}.getType());

return list;

}

public Map<Integer, String> GetJsonToHashMap(String jsonString){

HashMap<Integer,String> hashMap =

gson.fromJson(jsonString, new TypeToken<HashMap<Integer,String>>(){}.getType());

return hashMap;

}

public PersonBean GetJsonToPersonBean(String jsonString){

PersonBean personBeanArrayList =

gson.fromJson(jsonString, PersonBean.class);

return personBeanArrayList;

}

public FriendsBook GetJsonToFriendsBook(String jsonString){

FriendsBook friendsBook = gson.fromJson(jsonString, FriendsBook.class);

return friendsBook;

}

}

测试代码：

TestJson.Java

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package testJson;

public class TestJson {

private static final TestJson_1 tj1 = new TestJson_1();

private static final TestJson_2 tj2 = new TestJson_2();

public static void main(String[] args){

//Java Object to JSON String

System.out.println("TestStringToJson: "

+ tj1.GetStringToJson() + "\n");

System.out.println("TestArrayListToJson: "

+ tj1.GetArrayListToJson() + "\n");

System.out.println("TestHashMapToJson: "

+ tj1.GetHashMapToJson() + "\n");

System.out.println("TestPersonBeanToJson: "

+ tj1.GetPersonBeanToJson() + "\n");

System.out.println("TestFriendsBookToJson: \n"

+ tj1.GetFriendsBookToJson() + "\n");

/*

* reverse JSON String To Java Object

*/

System.out.println("/***********************JSON String To Java Object******************************************/\n");

String jsonToString = tj1.GetStringToJson();

System.out.println("Json To String: "

+ tj2.GetJsonToString(jsonToString) + "\n");

String jsonToArrayList_String_ = tj1.GetArrayListToJson();

System.out.println("Json To ArrayList----list[0]: "

+ tj2.GetJsonToArrayList(jsonToArrayList_String_).get(0) + "\n");

String jsonToHashMap = tj1.GetHashMapToJson();

System.out.println("Json To HashMap----hashMap.get(3): "

+ tj2.GetJsonToHashMap(jsonToHashMap).get(3) + "\n");

String jsonToPersonBean = tj1.GetPersonBeanToJson();

System.out.println("Json To PersonBean----personBean.getName(): "

+ tj2.GetJsonToPersonBean(jsonToPersonBean).getName() + "\n");

String jsonToFriendsBook = tj1.GetFriendsBookToJson();

System.out.println("Json To FriendsBook----friendsBook.getFriendsBook().get(0).getName(): "

+ tj2.GetJsonToFriendsBook(jsonToFriendsBook).getFriendsBook().get(0).getName() + "\n");

}

}

测试输出：