好用的json工具 jackson

附带时间 格式化配置

@Slf4j
public class JacksonTool {

    private final static ObjectMapper mapper;

    private final static ObjectMapper notNullMapper;

    static {
        mapper = new ObjectMapper();
        initConfig(mapper);
    }

    static {
        notNullMapper = new ObjectMapper();
        initConfig(notNullMapper);
        notNullMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    }
    /**
     * 初始化 jackson 配置
     * @param mapper
     */
    static void initConfig(ObjectMapper mapper){
        // 忽略json中在对象不存在对应属性
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        // 忽略空bean转json错误
        mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
        // 关闭日期转时间戳
        mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,false);
        mapper.setTimeZone(TimeZone.getTimeZone("GMT+8"));
        mapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
        JavaTimeModule javaTimeModule = new JavaTimeModule();
        //格式化时间格式
        javaTimeModule.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
        javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
        javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(DateTimeFormatter.ofPattern("HH:mm:ss")));

        //反序列化
        javaTimeModule.addDeserializer(LocalDateTime.class,new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
        javaTimeModule.addDeserializer(LocalDate.class,new LocalDateDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
        javaTimeModule.addDeserializer(LocalTime.class,new LocalTimeDeserializer(DateTimeFormatter.ofPattern("HH:mm:ss")));
        javaTimeModule.addDeserializer(Date.class, new DateDeserializers.DateDeserializer() {
            @SneakyThrows
            @Override
            public Date deserialize(JsonParser jsonParser, DeserializationContext dc) {
                String text = jsonParser.getText().trim();
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
                return sdf.parse(text);
            }
        });

        mapper.registerModule(javaTimeModule);
    }

    /**
     * json转对象
     *
     * @param jsonStr   json串
     * @param classType 对象类型
     * @return 对象
     */
    public static <T> T toEntity(String jsonStr, Class<T> classType) {

        if (StringUtils.isEmpty(jsonStr)) {
            log.warn("Json string {} is empty!", classType);
            return null;
        }

        try {
            return mapper.readValue(jsonStr, classType);
        } catch (IOException e) {
            log.error("json to entity error.", e);
        }
        return null;
    }

    /**
     * json转化为带泛型的对象
     *      new TypeReference<List<UserVo>>(){}
     * @param jsonStr       json字符串
     * @param typeReference 转化类型
     * @return 对象
     */
    public static <T> T toEntity(String jsonStr, TypeReference<T> typeReference) {
        if (StringUtils.isBlank(jsonStr) || typeReference == null) {
            return null;
        }
        try {
            return (T) mapper.readValue(jsonStr, typeReference);
        } catch (Exception e) {
            log.error("json to entity error.", e);
        }
        return null;
    }

    /**
     * 对象转json
     *
     * @param obj 对象
     * @return json串
     */
    public static String toJson(Object obj) {
        if (obj instanceof String) {
            return (String) obj;
        }
        try {
            return mapper.writeValueAsString(obj);
        } catch (Exception e) {
            log.error("obj to json error.", e);
        }
        return null;
    }

    /**
     * null 不参与序列化
     * @param obj
     * @return
     */
    public static String toJsonNotNull(Object obj) {
        if (obj instanceof String) {
            return (String) obj;
        }
        try {
            return notNullMapper.writeValueAsString(obj);
        } catch (Exception e) {
            log.error("obj to json error.", e);
        }
        return null;
    }

    /**
     * 对象转json(格式化的json)
     *
     * @param obj 对象
     * @return 格式化的json串
     */
    public static String toJsonWithFormat(Object obj) {
        if (obj == null) {
            return null;
        }

        if (obj instanceof String) {
            return (String) obj;
        }

        try {
            return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
        } catch (IOException e) {
            log.error("obj to json error.", e);
        }
        return null;
    }
}