Simple AbstractXmlReader for building RESTful web services with Jersey using Guava to find the generic parameter types. See http://codyaray.com/2013/01/finding-generic-type-parameters-with-guava for details.

AbstractXmlReader.java

package com.mydomain.myapp.resources.xml;
 
import java.io.IOException;
import java.io.InputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
 
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyReader;
import javax.xml.parsers.DocumentBuilder;
 
import com.google.common.base.Throwables;
import com.google.common.reflect.TypeToken;
 
import org.w3c.dom.Element;
import org.xml.sax.SAXException;
 
/**
 * Base class for Jersey XML readers.
 *
 * @param <T> the type of the domain object
 * @author codyaray
 * @since 7/15/12
 */
public abstract class AbstractXmlReader<T> implements MessageBodyReader<T> {
 
  @SuppressWarnings("serial")
  private final TypeToken<T> typeToken = new TypeToken<T>(getClass()) { };
  private final Type type = typeToken.getType();
 
  private final DocumentBuilder builder;
 
  protected AbstractXmlReader(DocumentBuilder builder) {
    this.builder = builder;
  }
 
  @Override
  public T readFrom(Class<T> type, Type genericType, Annotation[] annotations,
      MediaType mediaType, MultivaluedMap<String, String> httpHeaders, InputStream entityStream)
      throws IOException, WebApplicationException {
    try {
      return fromXml(builder.parse(entityStream).getDocumentElement());
    } catch (SAXException e) {
      throw Throwables.propogate(e);
    }
  }
 
  @Override
  public boolean isReadable(Class<?> type, Type genericType,
      Annotation[] annotations, MediaType mediaType) {
    return MediaType.TEXT_XML_TYPE.equals(mediaType) && this.type.equals(genericType);
  }
 
  /**
   * Subclasses implement this method to read the domain object from the xml dom.
   *
   * @param documentElement root document element
   * @return domain object
   * @throws org.xml.sax.SAXException
   */
  protected abstract T fromXml(Element documentElement) throws SAXException;
}