将 Jackson ObjectMapper 与 Java 8 可选值一起使用 [英] Using Jackson ObjectMapper with Java 8 Optional values

问题描述

我试图使用 Jackson 将一个类值写入具有 Optional 作为字段的 JSON:

I was trying to use Jackson to write a class value to JSON that has Optional as fields:

public class Test {
    Optional<String> field = Optional.of("hello, world!");

    public Optional<String> getField() {
        return field;
    }

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        System.out.println(mapper.writeValueAsString(new Test()));
    }
}

执行时，该类生成以下输出:

When executed, this class generates the following output:

{"field":{"present":true}}

我了解包含的存在/不存在字段，并且可以在读取 JSON 数据时解决它，但是我无法避免可选的实际内容从未写入输出的事实.:(

I understand the present/not present field being included and could work around it when reading the JSON data, however I can't get around the fact that the actual content of the optional is never written to the output. :(

除了根本不使用 ObjectMapper 之外，还有其他解决方法吗?

Any workarounds here except not using ObjectMapper at all?

推荐答案

你可以使用 jackson-datatype-jdk8 描述为:

You could use jackson-datatype-jdk8 which is described as:

支持新的 JDK8 特定类型，例如 Optional

Support for new JDK8-specific types, such as Optional

为了做到这一点:

• 添加 com.fasterxml.jackson.datatype:jackson-datatype-jdk8 作为依赖
• 向您的对象映射器注册模块:objectMapper.registerModule(new Jdk8Module());

这篇关于将 Jackson ObjectMapper 与 Java 8 可选值一起使用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！