Json转换利器Gson之实例三-Map处理(上)

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]