使用Google的Gson實現對象和json字符串之間的轉換

使用Google的Gson實現對象和json字符串之間的轉換

須要gson.jar

 

1.JsonUtil.java

package com.snail.json;

import java.lang.reflect.Type;
import com.google.gson.Gson;
/**
 * Java對象和JSON字符串相互轉化工具類
 * @author penghuaiyi
 * @date 2013-08-10
 */
public final class JsonUtil {

    private JsonUtil(){}

    /**
     * 對象轉換成json字符串
     * @param obj
     * @return
     */
    public static String toJson(Object obj) {
        Gson gson = new Gson();
        return gson.toJson(obj);
    }

    /**
     * json字符串轉成對象
     * @param str
     * @param type
     * @return
     */
    public static <T> T fromJson(String str, Type type) {
        Gson gson = new Gson();
        return gson.fromJson(str, type);
    }

    /**
     * json字符串轉成對象
     * @param str
     * @param type
     * @return
     */
    public static <T> T fromJson(String str, Class<T> type) {
        Gson gson = new Gson();
        return gson.fromJson(str, type);
    }

}

 2. Person.java

package com.snail.json;

public class Person {
    private int id;
    private String name;

    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;
    }

}

 3. Test.java

package com.snail.json;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import com.google.gson.reflect.TypeToken;

public class Test {

    /**
     * 通常對象的轉換
     */
    public static void objectToJson(){
        Person person = new Person();
        person.setId(1);
        person.setName("one");
         //javabean轉換成json字符串
        String jsonStr = JsonUtil.toJson(person);
        System.out.println(jsonStr);

        //json字符串轉換成javabean
        Person newPerson = JsonUtil.fromJson(jsonStr, Person.class);
        System.out.println(person == newPerson);
        System.out.println(newPerson.getId()+","+newPerson.getName());
    }

    /**
     * 複合結構數據轉換(List)
     */
    public static void listToJson(){
        Person person1 = new Person();
        person1.setId(1);
        person1.setName("one");

        Person person2 = new Person();
        person2.setId(2);
        person2.setName("two");

        List<Person> list = new ArrayList<Person>();
        list.add(person1);
        list.add(person2);

        //javabean轉換成json字符串
        String jsonStr = JsonUtil.toJson(list);
        System.out.println(jsonStr);


        //json字符串轉換成javabean對象
        List<Person> rtn = JsonUtil.fromJson(jsonStr, new TypeToken<List<Person>>(){}.getType());
        for(Person person : rtn){
            System.out.println(person.getId()+","+person.getName());
        }
    }

    /**
     * 複合結構數據轉換(Map)
     */
    public static void mapToJson(){
        Person person1 = new Person();
        person1.setId(1);
        person1.setName("one");
        Person person2 = new Person();
        person2.setId(2);
        person2.setName("two");

        Map<Integer,Person> map = new HashMap<Integer,Person>();
        map.put(person1.getId(), person1);
        map.put(person2.getId(), person2);

         //javabean轉換成json字符串
        String jsonStr = JsonUtil.toJson(map);
        System.out.println(jsonStr);

        //json字符串轉換成Map對象
        Map<Integer,Person> rtn = JsonUtil.fromJson(jsonStr, new TypeToken<Map<Integer,Person>>(){}.getType());
        for(Entry<Integer, Person> entry : rtn.entrySet()){
            Integer key = entry.getKey();
            Person newPerson = entry.getValue();
            System.out.println("key:"+key+","+newPerson.getId()+","+newPerson.getName());
        }
    }


    public static void main(String[] args) {
        objectToJson();
        System.out.println("****************************");
        listToJson();
        System.out.println("****************************");
        mapToJson();
    }



}