使用Google的Gson实现对象和json字符串之间的转换

使用Google的Gson实现对象和json字符串之间的转换

需要gson-1.4.jar

 

1.JsonUtil.java

package com.snail.json;

import java.lang.reflect.Type;
import com.google.gson.Gson;
/**
 * Java对象和JSON字符串相互转化工具类
 * @author penghuaiyi
 * @date 2013-08-10
 */
public final class JsonUtil {
	
	private JsonUtil(){}
	
    /**
     * 对象转换成json字符串
     * @param obj 
     * @return 
     */
    public static String toJson(Object obj) {
        Gson gson = new Gson();
        return gson.toJson(obj);
    }

    /**
     * json字符串转成对象
     * @param str  
     * @param type
     * @return 
     */
    public static <T> T fromJson(String str, Type type) {
        Gson gson = new Gson();
        return gson.fromJson(str, type);
    }

    /**
     * json字符串转成对象
     * @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 {
	
	/**
	 * 一般对象的转换
	 */
	public static void objectToJson(){
		Person person = new Person();
		person.setId(1);
		person.setName("one");
		 //javabean转换成json字符串
		String jsonStr = JsonUtil.toJson(person);
		System.out.println(jsonStr);
		
		//json字符串转换成javabean
		Person newPerson = JsonUtil.fromJson(jsonStr, Person.class);
		System.out.println(person == newPerson);
		System.out.println(newPerson.getId()+","+newPerson.getName());
	}
	
	/**
	 * 复合结构数据转换(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转换成json字符串
		String jsonStr = JsonUtil.toJson(list);
		System.out.println(jsonStr);
		
		
		//json字符串转换成javabean对象
		List<Person> rtn = JsonUtil.fromJson(jsonStr, new TypeToken<List<Person>>(){}.getType());
		for(Person person : rtn){
			System.out.println(person.getId()+","+person.getName());
		}
	}
	
	/**
	 * 复合结构数据转换(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转换成json字符串
		String jsonStr = JsonUtil.toJson(map);
		System.out.println(jsonStr);
		
		//json字符串转换成Map对象
		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();
	}
	
 

}