XMLContentFilterInterceptor.java

/* Copyright 2012 predic8 GmbH, www.predic8.com

   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 com.predic8.membrane.core.interceptor.xmlcontentfilter;

import javax.xml.xpath.XPathExpressionException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Required;

import com.predic8.membrane.annot.MCAttribute;
import com.predic8.membrane.annot.MCElement;
import com.predic8.membrane.core.exchange.Exchange;
import com.predic8.membrane.core.http.Message;
import com.predic8.membrane.core.http.Response;
import com.predic8.membrane.core.interceptor.AbstractInterceptor;
import com.predic8.membrane.core.interceptor.Outcome;

/**
 * @description <p>
 *              The <i>xmlContentFilter</i> removes certain XML elements from message bodies. The elements are described
 *              using an XPath expression.
 *              </p>
 * @explanation <p>
 *              If the XPath expression is simple enough, a StAX-Parser is used to determine whether the XPath might
 *              match a message at all. This can improve performance significantly, as a DOM tree does probably not have
 *              to to be constructed for every message. This is, for example, the case in <listing name="example"> <src
 *              lang="xml"> <xmlContentFilter xPath="//*[local-name()='Fault' and
 *              namespace-uri()='http://schemas.xmlsoap.org/soap/envelope/']//*[local-name()='stacktrace']" />
 *              </src> <caption>xmlContentFilter using a StAX-Parser for improved performance</caption> </listing> where
 *              the existence of the <Fault>-element is checked using the StAX-parser before the DOM is
 *              constructed.
 *              </p>
 *              <p>
 *              If the message body is not well-formed XML, it is left unchanged. If the message is XOP-encoded, the
 *              XPath-expression is run on the reconstituted message; if it matches, the message is replaced by the
 *              modified reconstituted message.
 *              </p>
 * @topic 3. Enterprise Integration Patterns
 */
@MCElement(name="xmlContentFilter")
public class XMLContentFilterInterceptor extends AbstractInterceptor {

	private static final Logger LOG = LoggerFactory.getLogger(XMLContentFilterInterceptor.class);

	private String xPath;
	private XMLContentFilter xmlContentFilter;

	public XMLContentFilterInterceptor() {
		setFlow(Flow.Set.REQUEST_RESPONSE);
	}

	public String getXPath() {
		return xPath;
	}

	/**
	 * @description An XPath 1.0 expression describing the elements to be removed from message bodies.
	 */
	@Required
	@MCAttribute
	public void setXPath(String xPath) {
		this.xPath = xPath;
		try {
			this.xmlContentFilter = new XMLContentFilter(xPath);
		} catch (XPathExpressionException e) {
			throw new RuntimeException(e);
		}
	}

	@Override
	public Outcome handleRequest(Exchange exc) throws Exception {
		return handleMessage(exc, exc.getRequest());
	}

	@Override
	public Outcome handleResponse(Exchange exc) throws Exception {
		return handleMessage(exc, exc.getResponse());
	}

	private Outcome handleMessage(Exchange exc, Message message) {
		try {
			xmlContentFilter.removeMatchingElements(message);
			return Outcome.CONTINUE;
		} catch (Exception e) {
			LOG.error("xmlContentFilter error", e);
			exc.setResponse(Response.internalServerError("xmlContentFilter error. See log for details.").build());
			return Outcome.ABORT;
		}
	}

}