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

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

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

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：