比較好用的工具類，要匯入Jackson-mapper-asl依賴。詳細看程式碼，其中DateTimeUtil是另外的工具類。

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
import
 
 org.codehaus.jackson.map.annotate.JsonSerialize.Inclusion;
import org.codehaus.jackson.type.JavaType;
import org.codehaus.jackson.type.TypeReference;

import java.io.IOException;
import java.text.SimpleDateFormat;

/**
 * Created by xcw on 2018/3/30.
 */
@Slf4j
public class JsonUtil {

    private static
 
 ObjectMapper objectMapper = new ObjectMapper();

    static {
        // 物件的所有欄位全部列入
        objectMapper.setSerializationInclusion(Inclusion.ALWAYS);
        // 取消預設轉換timestamps形式
        objectMapper.configure(SerializationConfig.Feature.WRITE_DATE_KEYS_AS_TIMESTAMPS, false);
        // 忽略空Bean轉Json的錯誤
 

        objectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS, false);
        // 所有日期格式統一為 yyyy:MM:dd HH:mm:ss
        objectMapper.setDateFormat(new SimpleDateFormat(DateTimeUtil.STANDARD_FORMAT));
        // 忽略在Json字串中存在，但在Java物件中不存在的對應屬性的狀況，防止錯誤
        objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    }

    /**
     * 物件返回Json字串
     * @param obj
     * @param <T>
     * @return
     */
    public static <T> String obj2String(T obj) {
        if (obj == null) {
            return null;
        }
        try {
            return obj instanceof String ? (String) obj : objectMapper.writeValueAsString(obj);
        } catch (Exception e) {
            log.warn("Parse object to String error", e);
            return null;
        }
    }

    /**
     * 物件返回格式化後的Json字串
     * @param obj
     * @param <T>
     * @return
     */
    public static <T> String obj2StringPretty(T obj) {
        if (obj == null) {
            return null;
        }
        try {
            return obj instanceof String ? (String) obj : objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
        } catch (Exception e) {
            log.warn("Parse Object to String error", e);
            return null;
        }
    }

    /**
     * Json字串轉成物件
     * @param str
     * @param clazz
     * @param <T>
     */
    public static <T> T string2Obj(String str, Class<T> clazz) {
        if (StringUtils.isEmpty(str) || clazz == null) {
            return null;
        }
        try {
            return clazz.equals(String.class) ? (T) str : objectMapper.readValue(str, clazz);
        } catch (Exception e) {
            log.warn("Parse String to Object error", e);
            return null;
        }
    }

    /**
     * 泛型反序列化
     * @param str
     * @param typeReference 對應返回值的型別
     * @param <T>
     * @return
     */
    public static <T> T string2Obj(String str, TypeReference<T> typeReference) {
        if (StringUtils.isEmpty(str) || typeReference == null) {
            return null;
        }

        try {
            return (T) (typeReference.getType().equals(String.class) ? str : objectMapper.readValue(str, typeReference));
        } catch (IOException e) {
            log.warn("Parse String to Object error", e);
            return null;
        }
    }

    /**
     * 泛型反序列化
     * @param str
     * @param collectionClass 集合的型別
     * @param elementClasses 集合中元素的型別
     * @param <T>
     * @return
     */
    public static <T> T string2Obj(String str, Class<?> collectionClass, Class<?>... elementClasses) {
        JavaType javaType = objectMapper.getTypeFactory().constructParametricType(collectionClass, elementClasses);
        try {
            return objectMapper.readValue(str, javaType);
        } catch (IOException e) {
            log.warn("Parse String to Object error", e);
            return null;
        }
    }
}