转载请出自出处：http://eksliang.iteye.com/blog/2175532
一、概述
Map保存的是键值对的形式，Json的格式也是键值对的，所以正常情况下，map跟json之间的转换应当是理所当然的事情。
二、Map参考实例
package com.ickes.json;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;
import com.ickes.json.daomain.User;
/**
* Gson对Map的处理
* @author Ickes
*
*/
public class MapTest {
public static void main(String[] args) {
/**
* 普通map处理
*/
Map<String,String> map = new HashMap<String,String>();
map.put("name","ickes");
map.put("pwd", "123");
Gson gson = new GsonBuilder()
.enableComplexMapKeySerialization()
.setPrettyPrinting()
.setDateFormat("yyyy-MM-dd HH:mm:ss")
.create();
//map的序列化
String json=gson.toJson(map);
System.out.println("map的序列化：\n"+json);
//map的反序列化
Type typeMap = new TypeToken<Map<String,String>>(){}.getType();
map = gson.fromJson(json,typeMap);
System.out.println("map的反序列化:");
for (Map.Entry<String,String> entry: map.entrySet()) {
System.out.println(entry.getKey()+"-"+entry.getValue());
}
/**
* /map对象测试
*/
Map<String,User> mapUser = new HashMap<String,User>();
User user1 = new User("A001", "xl","xl_123",24,12000F,new Date());
User user2 = new User("A002", "x2","xl_223",24,13000F,new Date());
mapUser.put("user1",user1);
mapUser.put("user2",user2);
json = gson.toJson(mapUser);
System.out.println("Map对象的序列化:\n"+json);
//map对象的反序列化
Type typeUser = new TypeToken<Map<String,User>>(){}.getType();
mapUser = gson.fromJson(json, typeUser);
System.out.println("map对象的反序列化:");
for (Map.Entry<String,User> entry: mapUser.entrySet()) {
System.out.println(entry.getKey()+"-"+entry.getValue());
}
/**
* 整合测试
*/
Map<String,List<User>> mapList = new HashMap<String,List<User>>();
List<User> users = new ArrayList<User>();
users.add(user1);
users.add(user2);
mapList.put("mapList",users);
//序列化
json = gson.toJson(mapList);
System.out.println("mapList的序列化：\n"+json);
//反序列化
Type typeMapList = new TypeToken<Map<String,List<User>>>(){}.getType();
mapList = gson.fromJson(json, typeMapList);
System.out.println("mapList对象的反序列化:");
for (Map.Entry<String,List<User>> entry: mapList.entrySet()) {
System.out.println(entry.getKey()+"-"+entry.getValue());
}
}
}
返回结果：
map的序列化：
{
"pwd": "123",
"name": "ickes"
}
map的反序列化:
pwd-123
name-ickes
Map对象的序列化:
{
"user2": {
"id": "A002",
"userName": "x2",
"userPwd": "xl_223",
"age": 24,
"price": 13000.0,
"birthday": "2015-01-13 16:06:48"
},
"user1": {
"id": "A001",
"userName": "xl",
"userPwd": "xl_123",
"age": 24,
"price": 12000.0,
"birthday": "2015-01-13 16:06:48"
}
}
map对象的反序列化:
user2-User [id=A002, userName=x2, userPwd=xl_223, age=24, price=13000.0, birthday=Tue Jan 13 16:06:48 CST 2015]
user1-User [id=A001, userName=xl, userPwd=xl_123, age=24, price=12000.0, birthday=Tue Jan 13 16:06:48 CST 2015]
mapList的序列化：
{
"mapList": [
{
"id": "A001",
"userName": "xl",
"userPwd": "xl_123",
"age": 24,
"price": 12000.0,
"birthday": "2015-01-13 16:06:48"
},
{
"id": "A002",
"userName": "x2",
"userPwd": "xl_223",
"age": 24,
"price": 13000.0,
"birthday": "2015-01-13 16:06:48"
}
]
}
mapList对象的反序列化:
mapList-[User [id=A001, userName=xl, userPwd=xl_123, age=24, price=12000.0, birthday=Tue Jan 13 16:06:48 CST 2015], User [id=A002, userName=x2, userPwd=xl_223, age=24, price=13000.0, birthday=Tue Jan 13 16:06:48 CST 2015]]
温馨提示：Gson在序列化Map时，默认情况下，是调用Key的toString方法得到它的JSON字符串的Key，对于简单类型和字符串类型，这没有问题，但是对于复杂数据对象，如果对象没有覆写toString方法，那么默认的toString方法将得到这个对象的Hash地址，通过调用GsonBuilder的enableComplexMapKeySerialization()来启用对Map键（key）的序列化.
三、一对多参考实例
下面实例提供了User(员工)对Dept(部门)一对多的映射关系
User实体类：
package com.ickes.json.daomain;
import java.util.Date;
/**
* @author Ickes
*/
public class User {
private String userName;
private String userPwd;
private Integer age;
private Date birthday;
public User(String userName, String userPwd, Integer age, Date birthday) {
super();
this.userName = userName;
this.userPwd = userPwd;
this.age = age;
this.birthday = birthday;
}
get()和set()方法省略.....!
@Override
public String toString() {
return "User [userName=" + userName + ", userPwd=" + userPwd + ", age="
+ age + ", birthday=" + birthday + "]";
}
}
Dept实体类：
package com.ickes.json.daomain;
import java.util.List;
public class Dept {
private String id;
private String deptName;
private List<User> users;
public Dept(String id, String deptName) {
super();
this.id = id;
this.deptName = deptName;
}
get()和set()方法省略......!
@Override
public String toString() {
return "Dept [id=" + id + ", deptName=" + deptName + ", users=" + users
+ "]";
}
}
测试实体类：
package com.ickes.json.daomain;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
/**
* Gson处理这种一对多的序列化
* @author Ickes
*
*/
public class DeptTest {
public static void main(String[] args) {
User user1 = new User("xl","xl_223",12100,new Date());
User user2 = new User("x2","xl_323",12300,new Date());
User user3 = new User("x3","xl_423",12300,new Date());
Dept dept = new Dept("D001","技术预研部");
List<User> users = new ArrayList<User>();
users.add(user1);
users.add(user2);
users.add(user3);
dept.setUsers(users);
Gson gson = new GsonBuilder()
.setPrettyPrinting()
.setDateFormat("yyyy-MM-dd HH:mm:ss")
.create();
String json=gson.toJson(dept);
System.out.println("一对多的序列化:\n"+json);
dept = gson.fromJson(json,Dept.class);
System.out.println("一对多的反序列化：\n"+dept);
}
}
返回结果如下：
一对多的序列化:
{
"id": "D001",
"deptName": "技术预研部",
"users": [
{
"userName": "xl",
"userPwd": "xl_223",
"age": 12100,
"birthday": "2015-01-13 18:57:23"
},
{
"userName": "x2",
"userPwd": "xl_323",
"age": 12300,
"birthday": "2015-01-13 18:57:23"
},
{
"userName": "x3",
"userPwd": "xl_423",
"age": 12300,
"birthday": "2015-01-13 18:57:23"
}
]
}
一对多的反序列化：
Dept [id=D001, deptName=技术预研部,
users=[User [userName=xl, userPwd=xl_223, age=12100, birthday=Tue Jan 13 18:57:23 CST 2015],
User [userName=x2, userPwd=xl_323, age=12300, birthday=Tue Jan 13 18:57:23 CST 2015],
User [userName=x3, userPwd=xl_423, age=12300, birthday=Tue Jan 13 18:57:23 CST 2015]
]]