【转】 Json转换利器Gson之实例三-Map处理

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(下一篇博客).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]

　

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:

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}]