JSON 学习 ：JSON数据串、对象、数组之间的转化

package utils;

import java.util.ArrayList;
import java.util.List;
import com.google.gson.Gson;
import com.google.gson.JsonObject;
import com.google.gson.reflect.TypeToken;
import java.lang.reflect.Type;
import bean.User;
import net.sf.json.JSONArray;

public class GsonUtil {

    /**
     * 将json数据串转换成对象数据
     * 
     * @param json
     * @param cls
     * @return
     * @throws Exception
     */
    public static <T> T fromJson(String json, Class<T> cls) throws Exception {
        T obj = null;
        Gson gson = new Gson();
        obj = cls.newInstance();
        obj = gson.fromJson(json, cls);
        return obj;
    }

    /**
     * 将对象转化成Json 数据串
     * 
     * @param obj
     * @return
     */
    public static String objToJson(Object obj) {
        return new Gson().toJson(obj);
    }

    /**
     * 将List Json数据串转换成List集合
     * 
     * @param json
     * @param clas
     * @return
     */
    public static <T> ArrayList<T> jsonToArrayList(String json, Class<T> cls) {
        Type type = new TypeToken<ArrayList<JsonObject>>() {
        }.getType();
        ArrayList<JsonObject> jsonObjects = new Gson().fromJson(json, type);

        ArrayList<T> arrayList = new ArrayList<>();
        for (JsonObject jsonObject : jsonObjects) {
            arrayList.add(new Gson().fromJson(jsonObject, cls));
        }
        return arrayList;
    }

    /**
     * 将List集合转化成Json数据串
     * 
     * @param list
     * @return
     */
    public static String listToJson(Object list) {
        JSONArray jsonArray = JSONArray.fromObject(list);
        return jsonArray.toString();
    }

    /**
     * test
     * 测试
     * @param args
     */
    public static void main(String[] args) {
        try {
            User u1 = new User();
            u1.setUid(100000);
            u1.setAddress("sasassdasd");
            u1.setAge(25);
            u1.setEmail("2515@qq.com");
            u1.setName("sai");
            String string = objToJson(u1);
            User u2 = new User();
            User u3 = new User();
            u3.setUid(100000);
            u3.setAddress("sasassdasd");
            u3.setAge(25);
            u3.setEmail("25175@qq.com");
            u3.setName("sai");
            List<User> uList = new ArrayList<User>();
            uList.add(u1);
            uList.add(u3);
            String s2 = listToJson(uList);

            List<User> uList1 = new ArrayList<User>();
            uList1 = jsonToArrayList(s2, User.class);

            for (User user : uList1) {
                System.out.println(user.toString());
            }

            u2 = fromJson(string, User.class);
            System.out.println(u2.toString());
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}