/**

  * Copyright 2005-2011 The Kuali Foundation

  *

  * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php

  *

  * 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.kuali.rice.kew.engine.node.var.schemes;

 import java.io.StringReader;

 import javax.xml.namespace.QName;

 import javax.xml.xpath.XPath;

 import javax.xml.xpath.XPathConstants;

 import javax.xml.xpath.XPathExpressionException;

 import javax.xml.xpath.XPathVariableResolver;

 import org.apache.log4j.Logger;

 import org.kuali.rice.kew.engine.RouteContext;

 import org.kuali.rice.kew.engine.node.BranchState;

 import org.kuali.rice.kew.engine.node.service.BranchService;

 import org.kuali.rice.kew.engine.node.var.Property;

 import org.kuali.rice.kew.engine.node.var.PropertyScheme;

 import org.kuali.rice.kew.rule.xmlrouting.XPathHelper;

 import org.kuali.rice.kew.service.KEWServiceLocator;

 import org.xml.sax.InputSource;

 /**

  * A PropertyScheme that resolves the Property by evaluating it as an XPath expression.

  * DocumentRouteHeaderValue variables are set on the XPath instance so they are accessible.

  * 

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 public class XPathScheme implements PropertyScheme {

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

     public String getName() {

         return "xpath";

     }

     public String getShortName() {

         return "xpath";

     }

     public Object load(Property property, final RouteContext context) {

         XPath xpath = XPathHelper.newXPath();

         final BranchService branchService = KEWServiceLocator.getBranchService();

         xpath.setXPathVariableResolver(new XPathVariableResolver() {

             public Object resolveVariable(QName name) {

                 LOG.debug("Resolving XPath variable: " + name);

                 String value = branchService.getScopedVariableValue(context.getNodeInstance().getBranch(), BranchState.VARIABLE_PREFIX + name.getLocalPart());

                 LOG.debug("Resolved XPath variable " + name + " to " + value);

                 return value;

             }

         });

         try {

             String docContent = context.getDocument().getDocContent();

             LOG.debug("Executing xpath expression '" + property.locator + "' in doc '" + docContent + "'");

             return xpath.evaluate(property.locator, new InputSource(new StringReader(docContent)), XPathConstants.STRING);

         } catch (XPathExpressionException xpee) {

             throw new RuntimeException("Error evaluating xpath expression '" + property.locator + "'", xpee);

         }

     }

 }