Jackson在Kotlin下全局自定义序列化器Long转String不生效

起因

雪花算法生成的主键传到前段后发生精度丢失，例如后端传入1397844263642378242，前端接收后变成1397844263642378000

因为Number的精度是16位，而雪花ID是19位

找了网上很多Java下配自定义序列化器的，改成Kotlin语法，如下

代码语言：javascript复制

@Configuration
class JacksonConfig {
    @Bean
    fun jacksonObjectMapper(builder: Jackson2ObjectMapperBuilder): ObjectMapper {
        val objectMapper: ObjectMapper = builder.createXmlMapper(false).build()
        val simpleModule = SimpleModule()
            .addSerializer(Long::class.java, ToStringSerializer.instance)
            .addSerializer(java.lang.Long.TYPE, ToStringSerializer.instance)
        objectMapper.registerModule(simpleModule)
        return objectMapper
    }
}

在Kotlin下怎么试都不生效，但是在字段上指定就可以

代码语言：javascript复制

@JsonSerialize(using=ToStringSerializer.class)
val id: Long?;

解决

中文互联网找了几遍没找到，去SO一下就找到答案了

How to use springboot kotlin jackson to globally set a custom Long type serializer?

答主是这样解释的：The issue with your code is that the val Long and val Long? from Kotlin are treated differently. The first will become a long whereas the second will become a Long (as it can be null).

但是这个回答提供的构造Bean的方式我不是很喜欢，因此我又找到了另一个帖子

Custom json serialization java primitives from kotlin by Jackson

最后的解决方案：

代码语言：javascript复制

@Configuration
class JacksonConfig {
    @Bean
    fun jacksonObjectMapper(builder: Jackson2ObjectMapperBuilder): ObjectMapper {
        val objectMapper: ObjectMapper = builder.createXmlMapper(false).build()
        val simpleModule = SimpleModule()
            .addSerializer(Long::class.javaPrimitiveType, ToStringSerializer.instance)
            .addSerializer(Long::class.javaObjectType, ToStringSerializer.instance)
        objectMapper.registerModule(simpleModule)
        return objectMapper
    }
}