杰克逊将 OffsetDateTime 序列化为 ISO-8601 在 jshell 中不起作用答案

【问题标题】：Jackson serialization of OffsetDateTime as ISO-8601 not working in jshell杰克逊将 OffsetDateTime 序列化为 ISO-8601 在 jshell 中不起作用
【发布时间】：2020-01-28 05:38:23
【问题描述】：

使用 jshell 版本 11.0.1，我正在尝试测试 java.time.OffsetDateTime 的 Jackson 序列化。我希望它以 ISO-8601 格式序列化，但它没有按预期工作。 为什么它仍然被序列化为对象而不是 ISO 8601？

这是我启动 jshell 的方式

jshell --class-path ~/.m2/repository/com/fasterxml/jackson/core/jackson-databind/2.8.9/jackson-databind-2.8.9.jar:~/.m2/repository/com/fasterxml/jackson/core/jackson-core/2.8.9/jackson-core-2.8.9.jar:~/.m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.8.9/jackson-annotations-2.8.9.jar:~/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jsr310/2.8.11/jackson-datatype-jsr310-2.8.11.jar

这是我在 jshell 中运行的代码

import com.fasterxml.jackson.databind.*;
import java.time.*;
import com.fasterxml.jackson.datatype.jsr310.*;
ObjectMapper mapper = new ObjectMapper();
mapper = mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
mapper.canSerialize(OffsetDateTime.class);
mapper.writeValueAsString(OffsetDateTime.now());

这是输出

|  Welcome to JShell -- Version 11.0.1
|  For an introduction type: /help intro

jshell> import com.fasterxml.jackson.databind.*;

jshell> import java.time.*;

jshell> import com.fasterxml.jackson.datatype.jsr310.*;

jshell> ObjectMapper mapper = new ObjectMapper();
mapper ==> com.fasterxml.jackson.databind.ObjectMapper@7fc229ab

jshell> mapper = mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
mapper ==> com.fasterxml.jackson.databind.ObjectMapper@7fc229ab

jshell> mapper.canSerialize(OffsetDateTime.class);
$6 ==> true

jshell> mapper.writeValueAsString(OffsetDateTime.now());
$7 ==> "{\"offset\":{\"totalSeconds\":-25200,\"id\":\"-07:00\",\"rules\":{\"fixedOffset\":true,\"transitions\":[],\"transitionRules\":[]}},\"month\":\"SEPTEMBER\",\"dayOfWeek\":\"FRIDAY\",\"dayOfYear\":270,\"nano\":911405000,\"year\":2019,\"monthValue\":9,\"dayOfMonth\":27,\"hour\":16,\"minute\":33,\"second\":6}"

为什么它仍然被序列化为对象而不是 ISO 8601？

【问题讨论】：

标签： java jackson java-time

【解决方案1】：

经过多次磕磕绊绊，我发现仅仅因为映射器说它可以序列化 OffsetDateTime.class 并不意味着它会将其识别为日期/时间类。我需要将此添加到映射器中。

mapper = mapper.registerModule(new JavaTimeModule());

现在输出是

jshell> import com.fasterxml.jackson.databind.*;

jshell> import java.time.*;

jshell> import com.fasterxml.jackson.datatype.jsr310.*;

jshell> ObjectMapper mapper = new ObjectMapper();
mapper ==> com.fasterxml.jackson.databind.ObjectMapper@7fc229ab

jshell> mapper = mapper.registerModule(new JavaTimeModule());
mapper ==> com.fasterxml.jackson.databind.ObjectMapper@7fc229ab

jshell> mapper = mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
mapper ==> com.fasterxml.jackson.databind.ObjectMapper@7fc229ab

jshell> mapper.canSerialize(OffsetDateTime.class);
$7 ==> true

jshell> mapper.writeValueAsString(OffsetDateTime.now());
$8 ==> "\"2019-09-27T16:41:07.921578-07:00\""

【讨论】：