/*
    * Copyright 2006 the original author or authors.
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.springframework.ws.server.endpoint.interceptor;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import javax.xml.transform.Source;
  import javax.xml.transform.Templates;
  import javax.xml.transform.Transformer;
  import javax.xml.transform.TransformerException;
  import javax.xml.transform.TransformerFactory;
  import javax.xml.transform.stream.StreamResult;
  import javax.xml.transform.stream.StreamSource;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.xml.sax.XMLReader;
  import org.xml.sax.helpers.XMLReaderFactory;
  
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.core.io.Resource;
  import org.springframework.util.Assert;
  import org.springframework.ws.WebServiceMessage;
  import org.springframework.ws.context.MessageContext;
  import org.springframework.ws.server.EndpointInterceptor;
  import org.springframework.xml.transform.ResourceSource;
  import org.springframework.xml.transform.TransformerObjectSupport;
  
  /**
   * Interceptor that transforms the payload of <code>WebServiceMessage</code>s using XSLT stylesheet. Allows for seperate
   * stylesheets for request and response. This interceptor is especially useful when supporting with multiple version of
   * a Web service: you can transform the older message format to the new format.
   * <p/>
   * The stylesheets to use can be set using the <code>requestXslt</code> and <code>responseXslt</code> properties. Both
   * of these are optional: if not set, the message is simply not transformed. Setting one of the two is required,
   * though.
   *
   * @author Arjen Poutsma
   * @see #setRequestXslt(org.springframework.core.io.Resource)
   * @see #setResponseXslt(org.springframework.core.io.Resource)
   * @since 1.0.0
   */
  public class PayloadTransformingInterceptor extends TransformerObjectSupport
          implements EndpointInterceptor, InitializingBean {
  
      private static final Log logger = LogFactory.getLog(PayloadTransformingInterceptor.class);
  
      private Resource requestXslt;
  
      private Resource responseXslt;
  
      private Templates requestTemplates;
  
      private Templates responseTemplates;
  
      /** Sets the XSLT stylesheet to use for transforming incoming request. */
      public void setRequestXslt(Resource requestXslt) {
          this.requestXslt = requestXslt;
      }
  
      /** Sets the XSLT stylesheet to use for transforming outgoing responses. */
      public void setResponseXslt(Resource responseXslt) {
          this.responseXslt = responseXslt;
      }
  
      /**
       * Transforms the request message in the given message context using a provided stylesheet. Transformation only
       * occurs if the <code>requestXslt</code> has been set.
       *
       * @param messageContext the message context
       * @return always returns <code>true</code>
       * @see #setRequestXslt(org.springframework.core.io.Resource)
       */
      public boolean handleRequest(MessageContext messageContext, Object endpoint) throws Exception {
          if (requestTemplates != null) {
              WebServiceMessage request = messageContext.getRequest();
              Transformer transformer = requestTemplates.newTransformer();
              transformMessage(request, transformer);
              logger.debug("Request message transformed");
          }
          return true;
      }
  
      /**
       * Transforms the response message in the given message context using a stylesheet. Transformation only occurs if
      * the <code>responseXslt</code> has been set.
      *
      * @param messageContext the message context
      * @return always returns <code>true</code>
      * @see #setResponseXslt(org.springframework.core.io.Resource)
      */
     public boolean handleResponse(MessageContext messageContext, Object endpoint) throws Exception {
         if (responseTemplates != null) {
             WebServiceMessage response = messageContext.getResponse();
             Transformer transformer = responseTemplates.newTransformer();
             transformMessage(response, transformer);
             logger.debug("Response message transformed");
         }
         return true;
     }
 
     private void transformMessage(WebServiceMessage message, Transformer transformer) throws TransformerException {
         ByteArrayOutputStream os = new ByteArrayOutputStream();
         transformer.transform(message.getPayloadSource(), new StreamResult(os));
         ByteArrayInputStream is = new ByteArrayInputStream(os.toByteArray());
         transform(new StreamSource(is), message.getPayloadResult());
     }
 
     /** Does nothing by default. Faults are not transformed. */
     public boolean handleFault(MessageContext messageContext, Object endpoint) throws Exception {
         return true;
     }
 
     public void afterPropertiesSet() throws Exception {
         if (requestXslt == null && responseXslt == null) {
             throw new IllegalArgumentException("Setting either 'requestXslt' or 'responseXslt' is required");
         }
         TransformerFactory transformerFactory = TransformerFactory.newInstance();
         XMLReader xmlReader = XMLReaderFactory.createXMLReader();
         xmlReader.setFeature("http://xml.org/sax/features/namespace-prefixes", true);
         if (requestXslt != null) {
             Assert.isTrue(requestXslt.exists(), "requestXslt \"" + requestXslt + "\" does not exit");
             if (logger.isInfoEnabled()) {
                 logger.info("Transforming request using " + requestXslt);
             }
             Source requestSource = new ResourceSource(xmlReader, requestXslt);
             requestTemplates = transformerFactory.newTemplates(requestSource);
         }
         if (responseXslt != null) {
             Assert.isTrue(responseXslt.exists(), "responseXslt \"" + responseXslt + "\" does not exit");
             if (logger.isInfoEnabled()) {
                 logger.info("Transforming response using " + responseXslt);
             }
             Source responseSource = new ResourceSource(xmlReader, responseXslt);
             responseTemplates = transformerFactory.newTemplates(responseSource);
         }
     }
 }