gson使用示例

gson是一個json庫，它可以方便的轉換java bean成json對象，也可以方便的將json對象轉換為java bean。

比起官方的Lib,Gson除了提供原本的Json相關功能外,更包含了Json和Java Object的互相轉換,而且許多常見的類型也可以轉換，特別是collection集合,非常方便

其項目地址：https://code.google.com/p/google-gson/

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
public class People {
    private int id;
    private String name;
    private float height;
    private double weight;
    private List friends = new ArrayList();
    private Map info = new HashMap();
    private Date birthday;
    private String comment;

public People(){
    id = 123456;
    name = "Jacky";
    height = new Float(172.2);
    weight = new Double(61.236);
    friends.add("Sam");
    friends.add("Jimmy");
    info.put("country","Taiwan");
    info.put("city","Taipei");
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    try {
        birthday = sdf.parse("1989-08-09");
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    comment = null;
}

public String toString(){
    String str = "";
    str += "id="+id;
    str += " name="+name;
    str += " height="+height;
    str += " weight="+weight;
    str += " ...etc";
    return str;
}

public static void main(String[] args) {
    People p = new People();
    //Gson gson = new Gson();
    //If you wanna allow null object
    Gson gson = new GsonBuilder().serializeNulls().create();
    String str = gson.toJson(p);
    System.out.println(str);

    People p2 = gson.fromJson(str, People.class);
    System.out.println(p2.toString());
}

}</pre>