Json转换利器Gson之实例四-Map处理(下)

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(上一篇博客),还可以是带有泛型的List(本文).本例中您要重点看如何将Json转回为带泛型的对象List,并且List中的泛型对象有多种实体.

实体类:

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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 + "]";

}

}

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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:

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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:

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{"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}]