找不到适合请求类型 JAXBElement 的 HttpMessageConverter

Question

我正在将 JAXB 对象发布到 REST 服务。生成的 class 没有 XMLRootElement，因此我使用 Object Factory createXMl 方法创建它。当我手动添加 XMLRootElement 时它起作用了，但这只是一种解决方法，因为 JAXB classes 总是在没有 XMLRootElement 的情况下生成。发布请求时编组的 XMl 似乎有一些问题。

    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_XML);
    String userAndPass = "Test:Test123";
    headers.add("Authorization", "Basic " + Base64Utility.encode(userAndPass.getBytes()));

    JAXBElement<DocumentDef> documentDef = PrintFactory.createPrintObjects();

    HttpEntity<JAXBElement<DocumentDef>> request = new HttpEntity<>(documentDef, headers);

    MultiValueMap<String, String> map = new LinkedMultiValueMap<String, String>();
    map.add("lang", "2");

    ResponseEntity<String> result = restTemplate.exchange(url, HttpMethod.POST, request, String.class, map);

PrintFactory.java

      public JAXBElement<DocumentDef> createPrintObjects() {

       DocumentDef documentDef = new DocumentDef();
       JAXBElement<DocumentDef> documentDefJAXBElement = factory.createXml(documentDef);
       return documentDefJAXBElement;
       }

ObjectFactory.java

        /**
 * Create an instance of {@link JAXBElement }{@code <}{@link DocumentDef }{@code >}}
 * 
 */
@XmlElementDecl(namespace = "http://www.example.com/testservice", name = "xml")
public JAXBElement<DocumentDef> createXml(DocumentDef value) {
    return new JAXBElement<DocumentDef>(_Xml_QNAME, DocumentDef.class, null, value);
}

错误：

org.springframework.web.client.RestClientException: Could not write request: no suitable HttpMessageConverter found for request type [javax.xml.bind.JAXBElement] and content type [application/xml]
at org.springframework.web.client.RestTemplate$HttpEntityRequestCallback.doWithRequest(RestTemplate.java:859)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:617)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:588)
at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:507)

以下 HttpMessageConverter 已注册：

org.springframework.http.converter.ByteArrayHttpMessageConverter@68022358, org.springframework.http.converter.StringHttpMessageConverter@7b3a8b9f, org.springframework.http.converter.StringHttpMessageConverter@645e9bc0, org.springframework.http.converter.ResourceHttpMessageConverter@7f438dba, org.springframework.http.converter.xml.SourceHttpMessageConverter@2c0def9c, org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter@46ee015c, org.springframework.http.converter.json.MappingJackson2HttpMessageConverter@2c833e50, org.springframework.http.converter.json.MappingJackson2HttpMessageConverter@339b6365, org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter@1e9a965b

Answer 1

嗯，确实它对你不起作用，因为：

JAXBElement<DocumentDef> documentDef = PrintFactory.createPrintObjects();
HttpEntity<JAXBElement<DocumentDef>> request = new HttpEntity<>(documentDef, headers);

同时Jaxb2RootElementHttpMessageConverter是为了这个：

* <p>This converter can read classes annotated with {@link XmlRootElement} and
* {@link XmlType}, and write classes annotated with {@link XmlRootElement},
* or subclasses thereof.

和

public boolean canWrite(Class<?> clazz, MediaType mediaType) {
    return (AnnotationUtils.findAnnotation(clazz, XmlRootElement.class) != null && canWrite(mediaType));
}

当你的JAXBElement完全没有@XmlRootElement时。

尝试找出没有 JAXBElement 包装器的解决方案。

Answer 2

我已经通过创建一个 .xjb 文件解决了这个问题，该文件在生成时自动将 XMLRootElement 注释附加到父 java class，如下所示：

<?xml version="1.0" encoding="UTF-8"?>
<jxb:bindings xmlns:jxb="http://java.sun.com/xml/ns/jaxb" xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
          xmlns:xs="http://www.w3.org/2001/XMLSchema"
          jxb:extensionBindingPrefixes="xjc" version="1.0">
<jxb:bindings schemaLocation="mySchema.xsd" node="/xs:schema">
    <jxb:globalBindings>
        <xjc:simple/>
    </jxb:globalBindings>
</jxb:bindings>

Answer 3

如果您需要 post 一个没有 XMLRootElement 注释的 jaxb 对象 ，一个解决方案是使用自定义 HttpMessageConverter :

// jaxb context specific to your xml elements JAXBContext jaxbContext = JAXBContext.newInstance(ObjectFactory.class.getPackage().getName()); // custom converter (see declaration below) JaxbElementHttpMessageConverter converter = new JaxbElementHttpMessageConverter(); converter.setJaxbContext(jaxbContext); RestTemplate template = new RestTemplate(); template.getMessageConverters().add(converter); // <--- here // your object needs to be wrapped around a JAXBElement YourRequestObject yourObject = ...; JAXBElement<YourRequestObject> element = new ObjectFactory().createYourRequestObject(request); HttpHeaders headers = new HttpHeaders(); headers.setContentType(MediaType.APPLICATION_XML); ResponseEntity<YourResponseObject> response = template.postForEntity("/your/url", HttpEntity<>(element, headers), YourResponseObject.class, params);

请注意，此转换器会尝试将任何对象转换为 JAXBElement，因此您需要：

确保您通过它的任何元素都可以 marshalled/unmarshalled 您指定的 jaxb 上下文；

将其添加到消息转换器列表的末尾，以便首先尝试更具体的消息转换器。

JaxbElementHttpMessageConverter定义如下：

/** * Implementation of {@link org.springframework.http.converter.HttpMessageConverter HttpMessageConverter} that can read and write XML using JAXB2. * * <p>This converter can read and write classes not annotated with {@link XmlRootElement} as long as they are wrapped into a {@link JAXBElement} and that a specific Jaxb context is provided. */ public class JaxbElementHttpMessageConverter extends AbstractJaxb2HttpMessageConverter<Object> { private JAXBContext jaxbContext; private EntityResolver entityResolver = NO_OP_ENTITY_RESOLVER; public void setJaxbContext(JAXBContext jaxbContext) { this.jaxbContext = jaxbContext; } public void setEntityResolver(EntityResolver entityResolver) { this.entityResolver = entityResolver; } @Override public boolean canRead(Class<?> clazz, MediaType mediaType) { return clazz.isAssignableFrom(JAXBElement.class) && canRead(mediaType); } @Override public boolean canWrite(Class<?> clazz, MediaType mediaType) { return clazz.isAssignableFrom(JAXBElement.class) && canWrite(mediaType); } @Override protected boolean supports(Class<?> clazz) { // should not be called, since we override canRead/Write throw new UnsupportedOperationException(); } @Override protected Object readFromSource(Class<?> clazz, HttpHeaders headers, Source source) { try { source = processSource(source); Unmarshaller unmarshaller = jaxbContext.createUnmarshaller(); JAXBElement<?> jaxbElement = unmarshaller.unmarshal(source, clazz); return jaxbElement.getValue(); } catch (UnmarshalException ex) { throw new HttpMessageNotReadableException("Could not unmarshal to [" + clazz + "]: " + ex.getMessage(), ex); } catch (JAXBException ex) { throw new HttpMessageConversionException("Could not instantiate JAXBContext: " + ex.getMessage(), ex); } } protected Source processSource(Source source) { if (source instanceof StreamSource) { StreamSource streamSource = (StreamSource) source; InputSource inputSource = new InputSource(streamSource.getInputStream()); try { XMLReader xmlReader = XMLReaderFactory.createXMLReader(); xmlReader.setEntityResolver(entityResolver); return new SAXSource(xmlReader, inputSource); } catch (SAXException ex) { logger.warn("Processing of external entities could not be disabled", ex); return source; } } else { return source; } } @Override protected void writeToResult(Object o, HttpHeaders headers, Result result) { try { Marshaller marshaller = jaxbContext.createMarshaller(); setCharset(headers.getContentType(), marshaller); marshaller.marshal(o, result); } catch (MarshalException ex) { throw new HttpMessageNotWritableException("Could not marshal [" + o + "]: " + ex.getMessage(), ex); } catch (JAXBException ex) { throw new HttpMessageConversionException("Could not instantiate JAXBContext: " + ex.getMessage(), ex); } } private void setCharset(MediaType contentType, Marshaller marshaller) throws PropertyException { if (contentType != null && contentType.getCharset() != null) { marshaller.setProperty(Marshaller.JAXB_ENCODING, contentType.getCharset().name()); } } private static final EntityResolver NO_OP_ENTITY_RESOLVER = new EntityResolver() { @Override public InputSource resolveEntity(String publicId, String systemId) { return new InputSource(new StringReader("")); } }; }

Answer 4

此问题与 MarshallingHttpMessageConverter class 中的 canWrite 和 canRead 方法有关。这些方法检查编组器和解组器是否支持 class。就我而言，启用 jaxb 元素支持很有帮助。


MarshallingHttpMessageConverter converter = new   MarshallingHttpMessageConverter();
Jaxb2Marshaller marshaller = new Jaxb2Marshaller();
marshaller.setSupportJaxbElementClass(true);
marshaller.setContextPath(ObjectFactory.class.getPackage().getName());
converter.setMarshaller(marshaller);

RestTemplate restTemplate = new RestTemplate();
restTemplate.getMessageConverters().add(converter);

找不到适合请求类型 JAXBElement 的 HttpMessageConverter

No suitable HttpMessageConverter found for request type JAXBElement

xml

spring

jaxb

spring-integration

spring-rest