1.pom.xml檔案

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.9.3</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId
 
>jackson-annotations</artifactId>
    <version>2.9.3</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.3</version>
</dependency>
<
 
dependency>
  <groupId>com.fasterxml.jackson.datatype</groupId>
  <artifactId>jackson-datatype-jsr310</artifactId>
  <version>2.9.3</version>
</dependency>

2.核心類ObjectMapper註冊為單例的Bean

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.context.annotation.Bean;
 
import org.springframework.context.annotation.Configuration;

@Configuration
public class UtilConfig {

    /**
     * 單例物件對映器
     * ObjectMapper 將jackson的這個核心類註冊為單例的Bean,防止在每一次序列化和反序列化時 new新的物件
     * @return {@link ObjectMapper}
     */
    @Bean
    public ObjectMapper singletonObjectMapper() {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.findAndRegisterModules();//可解決時間格式等一系列問題
        return objectMapper;
    }
}

3.JacksonUtil工具類

import cn.hutool.extra.spring.SpringUtil;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.commons.lang3.StringUtils;

import java.util.Collections;
import java.util.List;
import java.util.Map;

/**
 * 傑克遜跑龍套
 * 1.序列化類上，使用 @JsonInclude(JsonInclude.Include.NON_NULL) 序列化忽略所有null欄位
 * 2.時間欄位上，使用 @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss") 保持格式統一
 * 3.序列化類上，必須提供無參構造方法！！
 * 4.待續......
 *
 * @author xudong.shen
 * @date 2022/05/06
 */
public class JacksonUtil {


    /**
     * 序列化為JSON字串
     *
     * @param obj obj
     * @return {@link String}
     */
    public static String toJsonString(Object obj) {
        if (obj == null) return null;
        ObjectMapper mapper = SpringUtil.getBean(ObjectMapper.class);
        String result = null;
        try {
            result = mapper.writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return result;
    }


    /**
     * 解析物件
     * 反序列化為Object
     *
     * @param clazz   clazz
     * @param jsonStr json str
     * @return {@link T}
     */
    public static <T> T parseObject(String jsonStr, Class<T> clazz) {
        if (StringUtils.isBlank(jsonStr) || clazz == null) return null;
        ObjectMapper mapper = SpringUtil.getBean(ObjectMapper.class);
        T t = null;
        try {
            t = mapper.readValue(jsonStr, clazz);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return t;
    }


    /**
     * 解析List
     * 反序列化為List集合
     *
     * @param clazz       clazz
     * @param listJsonStr 列表json str
     * @return {@link List}<{@link T}>
     */
    public static <T> List<T> parseList(String listJsonStr, Class<T> clazz) {
        if (StringUtils.isBlank(listJsonStr) || clazz == null) return Collections.emptyList();
        ObjectMapper mapper = SpringUtil.getBean(ObjectMapper.class);
        List<T> list = Collections.emptyList();
        try {
            list = mapper.readValue(listJsonStr, List.class);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return list;
    }


    /**
     * 解析Map
     * 反序列化為Map集合
     * @param mapJsonStr 地圖json str
     * @param kClazz     k clazz
     * @param vClazz     v clazz
     * @return {@link Map}<{@link K}, {@link V}>
     */
    public static <K,V> Map<K,V> parseMap(String mapJsonStr, Class<K> kClazz, Class<V> vClazz) {
        if (StringUtils.isBlank(mapJsonStr) || kClazz == null || vClazz == null) return Collections.emptyMap();
        ObjectMapper mapper = SpringUtil.getBean(ObjectMapper.class);
        Map<K,V> map = Collections.EMPTY_MAP;
        try {
            map = mapper.readValue(mapJsonStr, mapper.getTypeFactory().constructParametricType(Map.class, kClazz, vClazz));
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return map;
    }


}

4.舉例子，如下這種複雜物件，都可以完成轉化

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonInclude;
import lombok.Data;

import java.time.LocalDateTime;
import java.util.List;
import java.util.Map;

@JsonInclude(JsonInclude.Include.NON_NULL)
@Data
public class Student {


    private Integer id;


    private String name;


    private Long age;

    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private LocalDateTime time;


    private Map<String,List<Student>> map;


}

一個完整的JSON示例字串：
{"1":{"id":1,"name":"德瑪西亞","time":"2022-05-06 17:53:01","map":{"第2組":[{"id":21,"name":"德瑪西亞21","time":"2022-05-06 17:53:01"},{"id":22,"name":"德瑪西亞22","time":"2022-05-06 17:53:01"},{"id":23,"name":"德瑪西亞23","time":"2022-05-06 17:53:01"}],"第1組":[{"id":11,"name":"德瑪西亞11","time":"2022-05-06 17:53:01"},{"id":12,"name":"德瑪西亞12","time":"2022-05-06 17:53:01"},{"id":13,"name":"德瑪西亞13","time":"2022-05-06 17:53:01"}]}},"2":{"id":2,"name":"德瑪西亞","time":"2022-05-06 17:53:01","map":{"第2組":[{"id":21,"name":"德瑪西亞21","time":"2022-05-06 17:53:01"},{"id":22,"name":"德瑪西亞22","time":"2022-05-06 17:53:01"},{"id":23,"name":"德瑪西亞23","time":"2022-05-06 17:53:01"}],"第1組":[{"id":11,"name":"德瑪西亞11","time":"2022-05-06 17:53:01"},{"id":12,"name":"德瑪西亞12","time":"2022-05-06 17:53:01"},{"id":13,"name":"德瑪西亞13","time":"2022-05-06 17:53:01"}]}}}