<dependency>

      <groupId>com.fasterxml.jackson.core</groupId>

      <artifactId>jackson-core</artifactId>

      <version>2.9.5</version>

    </dependency>　

 package com.example.myspring.transfer;

 import com.example.myspring.App;

 import com.fasterxml.jackson.core.JsonProcessingException;

 import com.fasterxml.jackson.databind.ObjectMapper;

 import org.junit.Test;

 import java.io.IOException;

 import java.util.Arrays;

 import java.util.HashMap;

 import java.util.Map;

 public class JacksonTest {

     private ObjectMapper objectMapper = new ObjectMapper();

     Map map = new HashMap();

     @Test

     public void toJsonTest1() throws JsonProcessingException {

         // 多种类型可以先封装为Map

         map.put("alibaba", new App());

         map.put("tengxun", Arrays.asList("weixin", "wangzherongyao"));

         map.put("hugh", null);

         map.put("DOU", "DOU");

         System.out.println(objectMapper.writeValueAsString(map));

         // {"alibaba":{},"DOU":"DOU","tengxun":["weixin","wangzherongyao"],"hugh":null}

     }

     @Test

     public void toJsonTest2() throws IOException {

         // 新加非类Stu属性six，且值为null，依然可以被识别

         String likeStu = "{\"sto\":\"001\",\"name\":\"xx\", \"six\":null}";

         Map<String, Object> mock = objectMapper.readValue(likeStu, Map.class); // {"sto":"001","name":"xx","six":null}

         System.out.println(objectMapper.writeValueAsString(mock));

     }

     public static class Stu{

         private String sto;

         private String name;

         public Stu(String sto, String name) {

             this.sto = sto;

             this.name = name;

         }

         public String getSto() {

             return sto;

         }

         public void setSto(String sto) {

             this.sto = sto;

         }

         public String getName() {

             return name;

         }

         public void setName(String name) {

             this.name = name;

         }

     }

 }