springboot自定義ObjectMapper序列化、配置序列化對LocalDateTime的支持

背景

1. 問題1：項目中使用默認自帶的jackson進行前后端交互，實現數據對象的序列化和反序列化，默認的ObjectMapper采用小駝峰的格式，但是調用其他業務的http接口時，ObjectMapper需要使用蛇形的格式，因此就需要自定義ObjectMapper，然后封裝RestTemplate。
2. 問題2：前后端交互時，JSR310日期序列化時，格式錯誤；

注意點

1. 自定義的ObjectMapper不能被IOC管理，因為Springboot默認的ObjectMapper生成條件是：只有當該實例不存在的時候才會創建！
2. 自定義時，需要支持JSR310的日期，否則序列化LocalDateTime、LocalDate、LocalTime時，就會返回錯誤的格式。
3. 使用springboot自帶的jackson，是不支持JSR310的日期，可以通過下面方式解決
   • 全局配置
   • 在實體類上增加 @JsonFormat(pattern = "yyyy-MM-dd")
   • 在controller方法參數中增加 @DateTimeFormat(pattern = "yyyy-MM-dd")

自定義ObjectMapper

@Slf4j
public class JsonFormatUtils {
    private static final DateTimeFormatter DATE_TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    private static final DateTimeFormatter TIME_FORMATTER = DateTimeFormatter.ofPattern("HH:mm:ss");
    public static final ObjectMapper objectMapper = new ObjectMapper();

    static {
        //取消時間的轉化格式，默認是時間戳,同時需要設置要表現的時間格式
        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
        objectMapper.configure(SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS, false);
        objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
        JavaTimeModule javaTimeModule = new JavaTimeModule();   // 默認序列化沒有實現，反序列化有實現
        javaTimeModule.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer(DATE_TIME_FORMATTER));
        javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer(DATE_FORMATTER));
        javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(TIME_FORMATTER));
        objectMapper.registerModule(javaTimeModule);
        // 設置時區
        objectMapper.setTimeZone(TimeZone.getDefault());
        // 設置格式化輸出
//        objectMapper.enable(SerializationFeature.INDENT_OUTPUT);
        // 設置蛇形格式
        objectMapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
    }

    public static String writeValueAsString(Object obj) {
        String result = null;
        try {
            result = objectMapper.writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            log.error("objectMapper writeValueAsString exception, e:", e);
        }
        return result;
    }

    public static <T> T readValue(String str, Class<T> tClass) {
        T t = null;
        try {
            t = objectMapper.readValue(str, tClass);
        } catch (JsonProcessingException e) {
            log.error("objectMapper readValue exception, e:", e);
        }
        return t;
    }
}

封裝RestTemplate

@Configuration
public class RestTemplateConfig {
    @Bean("otherRestTemplate")
    public RestTemplate algoRestTemplate() {
        // 使用apache的httpComponents，封裝restTemplate
        ClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory(httpClient());
        RestTemplate restTemplate = new RestTemplate(factory);
        // 使用自定義的ObjectMapper
        ObjectMapper objectMapper = JsonFormatUtils.objectMapper;
        MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter();
        messageConverter.setPrettyPrint(false);
        messageConverter.setObjectMapper(objectMapper);

        List<HttpMessageConverter<?>> messageConverters = restTemplate.getMessageConverters();
        messageConverters.removeIf(item -> item.getClass().getName().equals(MappingJackson2HttpMessageConverter.class.getName()));
        messageConverters.add(messageConverter);
        return restTemplate;
    }

    private HttpClient httpClient() {
        PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
        connectionManager.setMaxTotal(50);
        connectionManager.setDefaultMaxPerRoute(10);
        connectionManager.setValidateAfterInactivity(2000);
        RequestConfig requestConfig = RequestConfig.custom()
                .setSocketTimeout(10000)
                .setConnectTimeout(5000)
                .setConnectionRequestTimeout(1000)
                .build();
        return HttpClientBuilder.create().setDefaultRequestConfig(requestConfig).setConnectionManager(connectionManager).build();
    }
}

全局配置

底層默認是通過Jackson2ObjectMapperBuilderCustomizer創建的ObjectMapper

@Configuration
public class LocalDateTimeSerializerConfig {

    private static final DateTimeFormatter DATE_TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    private static final DateTimeFormatter TIME_FORMATTER = DateTimeFormatter.ofPattern("HH:mm:ss");


    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() {
        Map<Class<?>, JsonSerializer<?>> serializers = new HashMap<>();
        serializers.put(LocalDateTime.class, new LocalDateTimeSerializer(DATE_TIME_FORMATTER));
        serializers.put(LocalDate.class, new LocalDateSerializer(DATE_FORMATTER));
        serializers.put(LocalTime.class, new LocalTimeSerializer(TIME_FORMATTER));

        Map<Class<?>, JsonDeserializer<?>> deserializers = new HashMap<>();
        deserializers.put(LocalDateTime.class, new LocalDateTimeDeserializer(DATE_TIME_FORMATTER));
        deserializers.put(LocalDate.class, new LocalDateDeserializer(DATE_FORMATTER));
        deserializers.put(LocalTime.class, new LocalTimeDeserializer(TIME_FORMATTER));
        return builder -> builder.serializersByType(serializers).deserializersByType(deserializers);
    }
}