从未知的JAXBContext（XML）为JSON创建Marshaller [英] Create Marshaller for JSON from unknown JAXBContext (XML)

问题描述

我必须使用一个只提供JAXBContext的lib来为XML对象编组和解组XML数据。此外，我从未见过XML：只有JAXB对象传递给我。我现在需要的是将这些对象转换为XML，而不是转换为JSON。

I have to use a lib that only gives me a JAXBContext to marshall and unmarshall XML data to Java objects. Also I don't ever see XML: Only the JAXB objects are passed to me. What I now need is a conversion of those objects not to XML, but to JSON.

有没有办法从给定的JAXBContext创建一个marshaller，它可以用于生成JSON输出？

情况是我不仅仅是转换数据。我还有逻辑，它作用于XML和JSON之间的Java对象（并操纵数据）。这也是双向转型。 JAXBContext是关于XML和Java对象之间转换的信息 - 我的目的是重用这个上下文信息，而不必使用与JAXB不同的第二种技术实现第二次转换。 JAXBContext（及其Java对象）已经拥有有关XML结构的信息; JAXB自动识别该结构是节省时间的原因。

The situation is that I'm not only transforming data. I also have logic that acts on the Java objects between XML and JSON (and manipulates the data). Also it's a two-way transformation. The JAXBContext is the information I have about the transformation between XML and Java objects - My intention was to reuse this context information for not having to implement a second transformation with a second technology different to JAXB. The JAXBContext (and its Java objects) already have the information about the XML structure; The automated recognition of that structure by JAXB is the time-saving reason for using it.

推荐答案

如果您的JAXB类只使用基本注释，你可以看看 JacksonJAXBAnnotations ，允许杰克逊映射器识别JAXN注释。只需要四行代码（在最简单的编组情况下）。

If your JAXB classes just use the basic annotations, you can take a look at JacksonJAXBAnnotations, allows Jackson mapper to recognize JAXN annotations. Four lines of code (in the simplest marshalling case) would be all you would need.

ObjectMapper mapper = new ObjectMapper();
JaxbAnnotationModule module = new JaxbAnnotationModule();
mapper.registerModule(module);
mapper.writeValue(System.out, yourJaxbObject);

您可以在上面看到所有支持的注释的链接。您需要的maven工件是

You can see the link above for all the supported annotations. The maven artifact you'll need is

<dependency>
    <groupId>com.fasterxml.jackson.module</groupId>
    <artifactId>jackson-module-jaxb-annotations</artifactId>
    <version>2.4.0</version>
</dependency>

• 请参阅github以获取 jackson-module-jaxb-annotations - 注意这个工件有依赖关系在 jackson-core 和 jackson-databind 。因此，如果您不使用maven，那么您还需要确保下载这些工件


• See the github for jackson-module-jaxb-annotations - Note this artifact has dependencies on jackson-core and jackson-databind. So if you're not using maven, then you will need to make sure to download these artifacts also

简单例外：

JAXB类

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "hello",
    "world"
})
@XmlRootElement(name = "root")
public class Root {

    @XmlElement(required = true)
    protected String hello;
    @XmlElement(required = true)
    protected String world;

    // Getters and Setters
}

XML

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <hello>JAXB</hello>
    <world>Jackson</world>
</root>

测试

public class TestJaxbJackson {
    public static void main(String[] args) throws Exception {
        JAXBContext context = JAXBContext.newInstance(Root.class);
        Unmarshaller unmarshaller = context.createUnmarshaller();
        InputStream is = TestJaxbJackson.class.getResourceAsStream("test.xml");
        Root root = (Root)unmarshaller.unmarshal(is);
        System.out.println(root.getHello() + " " + root.getWorld());

        ObjectMapper mapper = new ObjectMapper();
        JaxbAnnotationModule module = new JaxbAnnotationModule();
        mapper.registerModule(module);
        mapper.writeValue(System.out, root);
    }
}

结果

{"hello":"JAXB","world":"Jackson"}





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更新





另见这篇文章。看起来MOXy也提供这种支持。

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Update

Also see this post. It looks like MOXy also offers this support.

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