如何在没有JAXBElement包装的情况下JSON-marshal JAXBElement包装的响应？ [英] How to JSON-marshal JAXBElement-wrapped responses without the JAXBElement wrapper?

问题描述

我有一个使用Spring（v4.0.5）的http服务。它的http端点是使用Spring Web MVC配置的。响应是由模式生成的JAXB2-anotated类。响应包含在 JAXBElement 中，因为生成的JAXB类没有运行 @XmlRootElement 注释（并且架构无法修改去医生）。我不得不通过XML编组来进行一些战斗;在任何情况下，它都在工作。

I have an http service that is using Spring (v4.0.5). Its http endpoints are configured using Spring Web MVC. The responses are JAXB2-anotated classes that are generated off of a schema. The responses are wrapped in JAXBElement as the generated JAXB classes do not sport @XmlRootElement annotations (and the schema cannot be modified to doctor this). I had to fight a bit with getting XML marshalling ti work; in any case, it is working.

现在我正在设置JSON编组。我遇到的是获取具有 JAXBElement 信封的JSON文档。

Now I am setting up JSON marshalling. What I am running into is getting JSON-documents that feature the JAXBElement "envelope".

{
  "declaredType": "io.github.gv0tch0.sotaro.SayWhat",
  "globalScope": true,
  "name": "{urn:io:github:gv0tch0:sotaro}say",
  "nil": false,
  "scope": "javax.xml.bind.JAXBElement$GlobalScope",
  "typeSubstituted": false,
  "value": {
    "what": "what",
    "when": "2014-06-09T15:56:46Z"
  }
}

我想要编组的只是值 -object：

What I would like to get marshalled instead is just the value-object:

{
  "what": "what",
  "when": "2014-06-09T15:56:46Z"
}

这是我的JSON编组配置（弹簧上下文配置的一部分）：

Here is my JSON marshalling config (part of the spring context configuration):

<bean id="jsonConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
  <property name="objectMapper" ref="jacksonMapper" />
  <property name="supportedMediaTypes" value="application/json" />
</bean>

<bean id="jacksonMapper" class="com.fasterxml.jackson.databind.ObjectMapper">
  <property name="dateFormat">
    <bean class="java.text.SimpleDateFormat">
      <constructor-arg type="java.lang.String" value="yyyy-MM-dd'T'HH:mm:ss'Z'" />
      <property name="timeZone">
        <bean class="java.util.TimeZone" factory-method="getTimeZone">
          <constructor-arg type="java.lang.String" value="UTC" />
        </bean>
      </property>
    </bean>
  </property>
</bean>

我希望这可以通过配置 ObjectMapper 。我想也可以推出我自己的序列化器。思考？建议？

I am hoping that this can be accomplished by configuring the ObjectMapper. I guess alternatively rolling out my own serializer may work. Thoughts? Suggestions?

推荐答案

您可以注册 mixin JAXBElement类的注释，它将放置注释，使其返回值为JSON表示。下面是一个示例：

You can register a mixin annotation for the JAXBElement class which would put the @JsonValue annotation on the JAXBElement.getValue() method making its return value to be the JSON representation. Here is an example:

一个示例.xsd chema文件，提供给 xjc 。

An example .xsd chema file that are given to xjc.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

<xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="item" type="Thing"/>

    <xs:complexType name="Thing">
        <xs:sequence>
            <xs:element name="number" type="xs:long"/>
            <xs:element name="string" type="xs:string" minOccurs="0"/>
        </xs:sequence>
    </xs:complexType>

</xs:schema>

Java主类：

public class JacksonJAXBElement {
    // a mixin annotation that overrides the handling for the JAXBElement
    public static interface JAXBElementMixin {
        @JsonValue
        Object getValue();
    }

    public static void main(String[] args) throws JAXBException, JsonProcessingException {
        ObjectFactory factory = new ObjectFactory();
        Thing thing = factory.createThing();
        thing.setString("value");
        thing.setNumber(123);
        JAXBElement<Thing> orderJAXBElement = factory.createItem(thing);

        System.out.println("XML:");
        JAXBContext jc = JAXBContext.newInstance(Thing.class);
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
        marshaller.marshal(orderJAXBElement, System.out);
        System.out.println("JSON:");

        ObjectMapper mapper = new ObjectMapper();
        mapper.addMixInAnnotations(JAXBElement.class, JAXBElementMixin.class);
        System.out.println(mapper.writerWithDefaultPrettyPrinter()
                .writeValueAsString(orderJAXBElement));
    }
}

输出：

XML:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<item>
    <number>123</number>
    <string>value</string>
</item>
JSON:
{
  "number" : 123,
  "string" : "value"
}

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