SpringBoot中java8的java.time.LocalDateTime类JsonFormat说明

Myth丶恋晨 2021-12-21 03:25 342阅读 0赞

# 问题概述 #

在SpringBoot中，需要对java8的java.time.LocalDateTime类进行个性化的JsonFormat。

# 处理前，默认处理的日期-时间效果 #

"create_time": { 
                "year": 2019,
                "month": "JUNE",
                "month_value": 6,
                "day_of_month": 27,
                "hour": 17,
                "minute": 40,
                "second": 43,
                "nano": 503000000,
                "day_of_week": "THURSDAY",
                "day_of_year": 178,
                "chronology": { 
                    "id": "ISO",
                    "calendar_type": "iso8601"
                }
            }

# 想要实现的效果 #

"create_time": "2019-06-27 17:40:43.503"

# 处理过程说明 #

## 1. 添加`jackson-datatype-jsr310`的引用 ##

<dependency>
    			<groupId>com.fasterxml.jackson.datatype</groupId>
    			<artifactId>jackson-datatype-jsr310</artifactId>
    			<version>2.4.0</version>
    		</dependency>

## 2. 在Java属性上添加`@JsonSerialize`和`@JsonFormat`注解说明 ##

/** * 创建时间 */
    	@JsonSerialize(using = LocalDateTimeSerializer.class)
    	@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss.SSS")
    	@Column(name = "create_time")
    	private LocalDateTime createTime = LocalDateTime.now();

# SpringBoot全局序列化配置 #

这时，可能有朋友会说：每个LocalDateTime，我都想按照固定的格式来进行Json序列化，一个一个实体类去加注解，岂不是很麻烦？  
别急，接下来我们来说一下全局配置：

需要在添加了`@Configuration`注解的配置类中，添加如下代码：

/** * 统一json输出风格 * See {@link com.fasterxml.jackson.databind.PropertyNamingStrategy.SnakeCaseStrategy} for details. * @param converters */
    	@Override
    	public void extendMessageConverters(List<HttpMessageConverter<?>> converters) { 
    		for (int i = 0; i < converters.size(); i++) { 
    			if (converters.get(i) instanceof StringHttpMessageConverter) { 
    				StringHttpMessageConverter stringHttpMessageConverter = new StringHttpMessageConverter(Charsets.UTF_8);
    				stringHttpMessageConverter.setWriteAcceptCharset(false);
    				converters.set(i, stringHttpMessageConverter);
    			}
    			if (converters.get(i) instanceof MappingJackson2HttpMessageConverter) { 
    				ObjectMapper objectMapper = new ObjectMapper();
    
    				SimpleModule simpleModule = new SimpleModule("JsonMapSerializer", Version.unknownVersion());
    
    				// 对LocalDateTime类，提供统一的序列化方式
    				DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
    				simpleModule.addSerializer(new LocalDateTimeSerializer(dateTimeFormatter));
    				objectMapper.registerModule(simpleModule);
    				// 统一返回数据的输出风格
    				objectMapper.setPropertyNamingStrategy(new PropertyNamingStrategy.SnakeCaseStrategy());
    				objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    				objectMapper.setTimeZone(TimeZone.getTimeZone("GMT+8"));
    				MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
    				converter.setObjectMapper(objectMapper);
    				converters.set(i, converter);
    				break;
    			}
    		}
    	}

然后，在具体类的成员变量上，就不用添加`@JsonSerialize`和`@JsonFormat`注解了。

参考：[stackoverflow:JSON Java 8 LocalDateTime format in Spring Boot][stackoverflow_JSON Java 8 LocalDateTime format in Spring Boot]  
[stackoverflow:Serialize LocalDateTime with only milliseconds with Jackson][stackoverflow_Serialize LocalDateTime with only milliseconds with Jackson]

[stackoverflow_JSON Java 8 LocalDateTime format in Spring Boot]: https://stackoverflow.com/questions/29956175/json-java-8-localdatetime-format-in-spring-boot
[stackoverflow_Serialize LocalDateTime with only milliseconds with Jackson]: https://stackoverflow.com/questions/54829133/serialize-localdatetime-with-only-milliseconds-with-jackson