Map的存储结构式Key/Value形式,Key 和 Value可以是普通类型,也可以是自己写的JavaBean(本文),还可以是带有泛型的List.

（GSON的GitHub项目页：https://github.com/google/gson）

JavaBean

本例中您要重点看如何将Json转回为普通JavaBean对象时TypeToken的定义.

实体类:

public class Point { private int x; private int y; public Point(int x, int y) { this.x = x; this.y = y; } public int getX() { return x; } public void setX(int x) { this.x = x; } public int getY() { return y; } public void setY(int y) { this.y = y; } @Override public String toString() { return "Point [x=" + x + ", y=" + y + "]"; } }

测试类:

import java.util.LinkedHashMap; import java.util.Map; import com.google.gson.Gson; import com.google.gson.GsonBuilder; import com.google.gson.reflect.TypeToken; public class GsonTest3 { public static void main(String[] args) { Gson gson = new GsonBuilder().enableComplexMapKeySerialization() .create(); Map<Point, String> map1 = new LinkedHashMap<Point, String>();// 使用LinkedHashMap将结果按先进先出顺序排列 map1.put(new Point(5, 6), "a"); map1.put(new Point(8, 8), "b"); String s = gson.toJson(map1); System.out.println(s);// 结果:[[{"x":5,"y":6},"a"],[{"x":8,"y":8},"b"]] Map<Point, String> retMap = gson.fromJson(s, new TypeToken<Map<Point, String>>() { }.getType()); for (Point p : retMap.keySet()) { System.out.println("key:" + p + " values:" + retMap.get(p)); } System.out.println(retMap); System.out.println("----------------------------------"); Map<String, Point> map2 = new LinkedHashMap<String, Point>(); map2.put("a", new Point(3, 4)); map2.put("b", new Point(5, 6)); String s2 = gson.toJson(map2); System.out.println(s2); Map<String, Point> retMap2 = gson.fromJson(s2, new TypeToken<Map<String, Point>>() { }.getType()); for (String key : retMap2.keySet()) { System.out.println("key:" + key + " values:" + retMap2.get(key)); } } }

结果:

[[{"x":5,"y":6},"a"],[{"x":8,"y":8},"b"]] key:Point [x=5, y=6] values:a key:Point [x=8, y=8] values:b {Point [x=5, y=6]=a, Point [x=8, y=8]=b} ---------------------------------- {"a":{"x":3,"y":4},"b":{"x":5,"y":6}} key:a values:Point [x=3, y=4] key:b values:Point [x=5, y=6]

泛型List

实体类:

import java.util.Date; public class Student { private int id; private String name; private Date birthDay; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Date getBirthDay() { return birthDay; } public void setBirthDay(Date birthDay) { this.birthDay = birthDay; } @Override public String toString() { return "Student [birthDay=" + birthDay + ", id=" + id + ", name=" + name + "]"; } } public class Teacher { private int id; private String name; private String title; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } @Override public String toString() { return "Teacher [id=" + id + ", name=" + name + ", title=" + title + "]"; } }

测试类:

package com.tgb.lk.demo.gson.test4; import java.util.ArrayList; import java.util.Date; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import com.google.gson.Gson; import com.google.gson.reflect.TypeToken; public class GsonTest4 { public static void main(String[] args) { Student student1 = new Student(); student1.setId(1); student1.setName("李坤"); student1.setBirthDay(new Date()); Student student2 = new Student(); student2.setId(2); student2.setName("曹贵生"); student2.setBirthDay(new Date()); Student student3 = new Student(); student3.setId(3); student3.setName("柳波"); student3.setBirthDay(new Date()); List<Student> stulist = new ArrayList<Student>(); stulist.add(student1); stulist.add(student2); stulist.add(student3); Teacher teacher1 = new Teacher(); teacher1.setId(1); teacher1.setName("米老师"); teacher1.setTitle("教授"); Teacher teacher2 = new Teacher(); teacher2.setId(2); teacher2.setName("丁老师"); teacher2.setTitle("讲师"); List<Teacher> teacherList = new ArrayList<Teacher>(); teacherList.add(teacher1); teacherList.add(teacher2); Map<String, Object> map = new LinkedHashMap<String, Object>(); map.put("students", stulist); map.put("teachers", teacherList); Gson gson = new Gson(); String s = gson.toJson(map); System.out.println(s); System.out.println("----------------------------------"); Map<String, Object> retMap = gson.fromJson(s, new TypeToken<Map<String, List<Object>>>() { }.getType()); for (String key : retMap.keySet()) { System.out.println("key:" + key + " values:" + retMap.get(key)); if (key.equals("students")) { List<Student> stuList = (List<Student>) retMap.get(key); System.out.println(stuList); } else if (key.equals("teachers")) { List<Teacher> tchrList = (List<Teacher>) retMap.get(key); System.out.println(tchrList); } } } }

输出结果:

{"students":[{"id":1,"name":"李坤","birthDay":"Jun 22, 2012 9:48:19 PM"},{"id":2,"name":"曹贵生","birthDay":"Jun 22, 2012 9:48:19 PM"},{"id":3,"name":"柳波","birthDay":"Jun 22, 2012 9:48:19 PM"}],"teachers":[{"id":1,"name":"米老师","title":"教授"},{"id":2,"name":"丁老师","title":"讲师"}]} ---------------------------------- key:students values:[{id=1.0, name=李坤, birthDay=Jun 22, 2012 9:48:19 PM}, {id=2.0, name=曹贵生, birthDay=Jun 22, 2012 9:48:19 PM}, {id=3.0, name=柳波, birthDay=Jun 22, 2012 9:48:19 PM}] [{id=1.0, name=李坤, birthDay=Jun 22, 2012 9:48:19 PM}, {id=2.0, name=曹贵生, birthDay=Jun 22, 2012 9:48:19 PM}, {id=3.0, name=柳波, birthDay=Jun 22, 2012 9:48:19 PM}] key:teachers values:[{id=1.0, name=米老师, title=教授}, {id=2.0, name=丁老师, title=讲师}] [{id=1.0, name=米老师, title=教授}, {id=2.0, name=丁老师, title=讲师}]