從GitHub下載GSON：https://github.com/google/gson
Gson的應(yīng)用主要為toJson與fromJson兩個(gè)轉(zhuǎn)換函數(shù)，而在使用這種對(duì)象轉(zhuǎn)換之前需先創(chuàng)建好對(duì)象的類別以及其成員才能成功的將JSON字符串成功轉(zhuǎn)換成相對(duì)應(yīng)的對(duì)象。

 class Examples {
  private int answer1 = 100;
  private String answer2 = "Hello world!";
  Examples(){
  }   // default constructor
 }

序列化JAVA對(duì)象成JSON字符串

  Examples example1 = new Examples();
  Gson gson = new Gson();
  String json = gson.toJson(example1);

json結(jié)果將是

{"answer1":100,"answer2":"Hello world!"}

反序列化JSON字符串成對(duì)應(yīng)的JAVA對(duì)象

Examples example2= gson.fromJson(json,Examples.class);

==> example2即與example1相同

對(duì)象example1通過(guò)toJson序列化成JSON字符串傳遞，再宣告一個(gè)對(duì)象example2為接收了JSON后通過(guò)fromJson反序列化成example2，故example1與example2相同

示例：

import java.util.ArrayList; 
import java.util.Arrays; 
import java.util.Collection; 
import java.util.HashMap; 
import java.util.Map; 
  
import com.google.gson.Gson; 
import com.google.gson.reflect.TypeToken; 
  
class User{ 
  public User(String name,int age,StringBuffer sex,boolean isChild){ 
   this.name = name; 
   this.age = age; 
   this.sex = sex; 
   this.isChild = isChild; 
  } 
  private String name; 
  private int age; 
  private StringBuffer sex; 
  private boolean isChild; 
  public String toString(){ 
   return "{name="+name+";age="+age+";sex="+sex+";isChild="+isChild+"}"; 
  } 
  public int hashCode(){ 
   return name.hashCode()*100+age; 
  } 
} 
  
public class GsonTest { 
  public static void main(String[] args) { 
   Gson gson = new Gson(); 
    
   System.out.println("1普通的Bean的轉(zhuǎn)換**************************"); 
   System.out.println("將一個(gè)Bean轉(zhuǎn)換成為json字符串->"); 
   User user1 = new User("鳳姐",12,new StringBuffer("未知"),true); 
   System.out.println("轉(zhuǎn)換之前的user1"+user1); 
   String json = gson.toJson(user1); 
   System.out.println("User對(duì)象轉(zhuǎn)換成為Json字符串，json==="+json); 
    
   System.out.println("***************************"); 
   System.out.println("將一個(gè)json字符串轉(zhuǎn)換成為Bean->"); 
   User user2 = gson.fromJson(json, User.class); 
   System.out.println("轉(zhuǎn)換成為的user2=="+user2); 
   System.out.println(); 
    
   System.out.println("2Collection集合的轉(zhuǎn)換**************************"); 
   System.out.println("將一個(gè)Bean的List集合轉(zhuǎn)換成為json字符串->"); 
   Collection<User> userList1 = new ArrayList<User>(); 
   for(int i=0;i<3;i++){ 
    User user = new User("如花",10+i,new StringBuffer("男"),false); 
    userList1.add(user); 
   } 
   json = gson.toJson(userList1); 
   System.out.println("User的List集合對(duì)象轉(zhuǎn)換成為Json字符串，json==="+json); 
    
   System.out.println("***************************"); 
   System.out.println("將一個(gè)json字符串轉(zhuǎn)換成為Bean的List集合->"); 
   Collection<User> userList2 = 
      gson.fromJson(json, 
         new TypeToken<Collection<User>>(){}.getType()); 
   System.out.println("轉(zhuǎn)換成為的User的List集合，userList2="+userList2); 
   System.out.println(); 
    
   System.out.println("3Array數(shù)組的轉(zhuǎn)換**************************"); 
   System.out.println("將一個(gè)Bean的Array數(shù)組轉(zhuǎn)換成為json字符串->"); 
   User [] userArray1 = new User[3]; 
   for(int i=0;i<userArray1.length;i++){ 
    userArray1[i] = new User("芙蓉",20,new StringBuffer("人妖"),true); 
   } 
   json = gson.toJson(userArray1); 
   System.out.println("User的數(shù)組對(duì)象轉(zhuǎn)換成為Json字符串,json==="+json); 
    
   System.out.println("***************************"); 
   System.out.println("將一個(gè)json字符串轉(zhuǎn)換成為Bean的數(shù)組對(duì)象->"); 
   User [] userArray2 = gson.fromJson(json, new TypeToken<User[]>(){}.getType()); 
   System.out.println("轉(zhuǎn)換成為的User的數(shù)組對(duì)象,userArray2="+Arrays.toString(userArray2)); 
   System.out.println(); 
    
   System.out.println("4Map的轉(zhuǎn)換**************************"); 
   System.out.println("將一個(gè)Bean的Map轉(zhuǎn)換成為json字符串->"); 
   Map<String,User> map1 = new HashMap<String,User>(); 
   for(int i=0;i<3;i++){ 
    map1.put(""+(i+10), userArray1[i]); 
   } 
   json = gson.toJson(map1); 
   System.out.println("User的Map集合轉(zhuǎn)換成為Json字符串,json==="+json); 
    
   System.out.println("***************************"); 
   System.out.println("將一個(gè)json字符串轉(zhuǎn)換成為Bean的數(shù)組對(duì)象->"); 
   Map<String,User> map2 = 
      gson.fromJson(json, 
         new TypeToken<Map<String,User>>(){}.getType()); 
   System.out.println("轉(zhuǎn)換成為的User的數(shù)組對(duì)象，map2=="+map2); 
  } 
}

運(yùn)行結(jié)果：

1普通的Bean的轉(zhuǎn)換************************** 
將一個(gè)Bean轉(zhuǎn)換成為json字符串-> 
轉(zhuǎn)換之前的user1{name=鳳姐;age=12;sex=未知;isChild=true} 
User對(duì)象轉(zhuǎn)換成為Json字符串，json==={"name":"鳳姐","age":12,"sex":"未知","isChild":true} 
*************************** 
將一個(gè)json字符串轉(zhuǎn)換成為Bean-> 
轉(zhuǎn)換成為的user2=={name=鳳姐;age=12;sex=未知;isChild=true} 
 
2Collection集合的轉(zhuǎn)換************************** 
將一個(gè)Bean的List集合轉(zhuǎn)換成為json字符串-> 
User的List集合對(duì)象轉(zhuǎn)換成為Json字符串，json===[{"name":"如花","age":10,"sex":"男","isChild":false},{"name":"如花","age":11,"sex":"男","isChild":false},{"name":"如花","age":12,"sex":"男","isChild":false}] 
*************************** 
將一個(gè)json字符串轉(zhuǎn)換成為Bean的List集合-> 
轉(zhuǎn)換成為的User的List集合，userList2=[{name=如花;age=10;sex=男;isChild=false}, {name=如花;age=11;sex=男;isChild=false}, {name=如花;age=12;sex=男;isChild=false}] 
 
3Array數(shù)組的轉(zhuǎn)換************************** 
將一個(gè)Bean的Array數(shù)組轉(zhuǎn)換成為json字符串-> 
User的數(shù)組對(duì)象轉(zhuǎn)換成為Json字符串,json===[{"name":"芙蓉","age":20,"sex":"人妖","isChild":true},{"name":"芙蓉","age":20,"sex":"人妖","isChild":true},{"name":"芙蓉","age":20,"sex":"人妖","isChild":true}] 
*************************** 
將一個(gè)json字符串轉(zhuǎn)換成為Bean的數(shù)組對(duì)象-> 
轉(zhuǎn)換成為的User的數(shù)組對(duì)象,userArray2=[{name=芙蓉;age=20;sex=人妖;isChild=true}, {name=芙蓉;age=20;sex=人妖;isChild=true}, {name=芙蓉;age=20;sex=人妖;isChild=true}] 
 
4Map的轉(zhuǎn)換************************** 
將一個(gè)Bean的Map轉(zhuǎn)換成為json字符串-> 
User的Map集合轉(zhuǎn)換成為Json字符串,json==={"10":{"name":"芙蓉","age":20,"sex":"人妖","isChild":true},"11":{"name":"芙蓉","age":20,"sex":"人妖","isChild":true},"12":{"name":"芙蓉","age":20,"sex":"人妖","isChild":true}} 
*************************** 
將一個(gè)json字符串轉(zhuǎn)換成為Bean的數(shù)組對(duì)象-> 
轉(zhuǎn)換成為的User的數(shù)組對(duì)象，map2=={10={name=芙蓉;age=20;sex=人妖;isChild=true}, 11={name=芙蓉;age=20;sex=人妖;isChild=true}, 12={name=芙蓉;age=20;sex=人妖;isChild=true}}

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