How to set custom ValidationEventHandler on JAXB u

问题:

We’re using JAX-WS in combination with JAXB to receive and parse XML web service calls. It’s all annotation-based, i.e. we never get hold of the JAXBContext in our code. I need to set a custom ValidationEventHandler on the unmarshaller, so that if the date format for a particular field is not accepted, we can catch the error and report something nice back in the response. We have a XMLJavaTypeAdapter on the field in question, which does the parsing and throws an exception. I can’t see how to set a ValidationEventHandler onto the unmarshaller using the annotation-based configuration that we have. Any ideas?

Note: same question as this comment which is currently unanswered.

回答1:

I have been struggling with this issue during the last week and finally i have managed a working solution. The trick is that JAXB looks for the methods beforeUnmarshal and afterUnmarshal in the object annotated with @XmlRootElement.

..
@XmlRootElement(name="MSEPObtenerPolizaFechaDTO")
@XmlAccessorType(XmlAccessType.FIELD)

public class MSEPObtenerPolizaFechaDTO implements Serializable {
..

public void beforeUnmarshal(Unmarshaller unmarshaller, Object parent) throws JAXBException, IOException, SAXException {
        unmarshaller.setSchema(Utils.getSchemaFromContext(this.getClass()));
        unmarshaller.setEventHandler(new CustomEventHandler());
  }

  public void afterUnmarshal(Unmarshaller unmarshaller, Object parent) throws JAXBException {
        unmarshaller.setSchema(null);
        unmarshaller.setEventHandler(null);
  }

Using this ValidationEventHandler:

public class CustomEventHandler implements ValidationEventHandler{

      @Override
      public boolean handleEvent(ValidationEvent event) {
            if (event.getSeverity() == event.ERROR ||
                        event.getSeverity() == event.FATAL_ERROR)
            {
                  ValidationEventLocator locator = event.getLocator();
                  throw new RuntimeException(event.getMessage(), event.getLinkedException());
            }
            return true;
      }
}

}

And this is the method getSchemaFromContext created in your Utility class:

  @SuppressWarnings("unchecked")
  public static Schema getSchemaFromContext(Class clazz) throws JAXBException, IOException, SAXException{
        JAXBContext jc = JAXBContext.newInstance(clazz);
        final List<ByteArrayOutputStream> outs = new ArrayList<ByteArrayOutputStream>();
        jc.generateSchema(new SchemaOutputResolver(){
              @Override
              public Result createOutput(String namespaceUri,
                         String suggestedFileName) throws IOException {
              ByteArrayOutputStream out = new ByteArrayOutputStream();
              outs.add(out);
              StreamResult streamResult = new StreamResult(out);
              streamResult.setSystemId("");
              return streamResult;
              }
        });
        StreamSource[] sources = new StreamSource[outs.size()];
        for (int i = 0; i < outs.size(); i++) {
              ByteArrayOutputStream out = outs.get(i);
              sources[i] = new StreamSource(new ByteArrayInputStream(out.toByteArray()), "");
        }
        SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
        return sf.newSchema(sources);
  }