json对象 java对象 和 string 之间的转换  


import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.TypeReference;

import dyyx.dto.Pet;


public class FastjsonTransTest {

	public static void main(String[] args) throws Exception {

		System.out.println("hello,FastjsonTransTest," + new Date());
                Pet pet1 = new Pet("cat",1,new Date());
                Pet pet2 = new Pet("tiger",3,new Date());
                List<Pet> pets = new ArrayList<Pet>();
		pets.add(pet1);
		pets.add(pet2);
		// Java 对象转string
		String petstr = JSON.toJSONString(pet1);
		String petsstr = JSON.toJSONString(pets);
		
		System.out.println(petstr);
		System.out.println(petsstr);
		
		// string 转 json对象
		JSONObject pet1JsonObject = JSON.parseObject(petstr);
		//  java.lang.ClassCastException: com.alibaba.fastjson.JSONArray cannot be cast to com.alibaba.fastjson.JSONObject
		// JSONObject petsJsonObject = JSON.parseObject(petsstr);
		JSONArray petsJsonArray = JSON.parseArray(petsstr);
		
		// json对象 转 string
		System.out.println(JSON.toJSONString(pet1JsonObject));
		System.out.println(JSON.toJSONString(petsJsonArray));
		
		// string 转 java对象 
		Pet pet1JavaObject = JSON.parseObject(petstr, Pet.class);
		System.out.println(pet1JavaObject);
		List  petsJavaObject = JSON.parseObject(petsstr, List.class);
		//  JSONObject
		for(Object item:petsJavaObject){
			System.out.println(item+","+item.getClass());
		}
		List<Pet> petsJavaObject2 = JSON.parseObject(petsstr, new TypeReference<List<Pet>>() {});
		for(Pet item:petsJavaObject2){
			System.out.println(item+","+item.getClass());
		}

		// json对象 转 java对象
		// 需要默认构造函数
		Pet pet1JavaObject2 = pet1JsonObject.toJavaObject(Pet.class);
		System.out.println(pet1JavaObject2);
		
		List<Pet> petsJavaObject3 = petsJsonArray.toJavaObject(new TypeReference<List<Pet>>() {});
		for(Pet item:petsJavaObject3){
			System.out.println(item+"||"+item.getClass());
		}
		
	}
}


完整代码
https://gitee.com/dyyx/demos/blob/master/jackson/src/test/java/dyyx/FastjsonTransTest.java