Json与对象之间的转化

1.　　对象转json：　

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class TestJsonAndObject {
    /**
     * 对象转化为json
     * @throws JsonProcessingException 
     */
    @Test
    public void ObjectToJson() throws JsonProcessingException{
        //引入Jackson Json处理工具包
        User user = new User();
        user.setId(1);
        user.setName("Tom");
        user.setAge(18);
        user.setSex("男");

        ObjectMapper objectMapper = new ObjectMapper();
        //转化时其实调用的是对象身上的get方法
        String json = objectMapper.writeValueAsString(user);
        System.out.println(json);
    }
}

输出：{"id":1,"name":"Tom","age":18,"sex":"男"}

2.　　json转对象：

    @Test
    public void jsonToObject() throws JsonParseException, JsonMappingException, IOException{
        String json = "{"id":1,"name":"Tom","age":18,"sex":"男"}";
        ObjectMapper objectMapper = new ObjectMapper();
        User user = objectMapper.readValue(json, User.class);
        System.out.println(user);
    }
输出：User [id=1, name=Tom, age=18, sex=男]

3.　　复杂格式转 ：

@Test
public void jsonOA() throws IOException{
        /**
         * 1.将多个对象转化为json
         */
        List<User> userList = new ArrayList<>();
        
        User user1 = new User();
        user1.setId(1);
        user1.setName("Tom");
        user1.setAge(18);
        user1.setSex("男");
        
        User user2 = new User();
        user2.setId(2);
        user2.setName("TomAA");
        user2.setAge(19);
        user2.setSex("女");
        
        userList.add(user1);
        userList.add(user2);
        
        ObjectMapper objectMapper = new ObjectMapper();
        String json = objectMapper.writeValueAsString(userList);
        System.out.println(json);
        /**
         * 2.将复杂格式的json转化为对象，List集合
         */
       // List<User> user = objectMapper.readValue(json, userList.getClass());　　//报警告...
       // System.out.println(user);

　　　　　//不报警告...
　　　　　User[] users = objectMapper.readValue(json, User[].class);
　　　　　//将数组转化为list　　　　　　
　　　　　List<User> asList = Arrays.asList(users);
　　　　　System.out.println(asList);

    }

输出1：[{"id":1,"name":"Tom","age":18,"sex":"男"},{"id":2,"name":"TomAA","age":19,"sex":"女"}]

输出2：[{id=1, name=Tom, age=18, sex=男}, {id=2, name=TomAA, age=19, sex=女}]

输出3，不报警告：[User [id=1, name=Tom, age=18, sex=男], User [id=2, name=TomAA, age=19, sex=女]]