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.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();  
    }  
      
   
  
}