Json转换利器Gson之实例四-Map处理(下)

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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:

[java] view plaincopy
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 + "]";  
    }  
  
}  

[java] view plaincopy
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:

[java] view plaincopy
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:

[plain] view plaincopy
{"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}]  

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