/*

  * $Id: MVELAttributeEvaluator.java 833737 2009-11-07 19:17:09Z apetrelli $

  *

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you 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.apache.tiles.mvel;

 import org.apache.tiles.context.TilesRequestContextHolder;

 import org.apache.tiles.evaluator.AbstractAttributeEvaluator;

 import org.apache.tiles.request.Request;

 import org.mvel2.MVEL;

 import org.mvel2.integration.VariableResolverFactory;

 /**

  * Allows to use MVEL as the language to evaluate attribute values.

  *

  * @version $Rev: 833737 $ $Date: 2009-11-08 06:17:09 +1100 (Sun, 08 Nov 2009) $

  * @since 2.2.0

  */

 public class MVELAttributeEvaluator extends AbstractAttributeEvaluator {

     /**

      * Holds the Tiles request context of the current thread.

      */

     private TilesRequestContextHolder requestHolder;

     /**

      * Resolves variables when starting from the root.

      *

      * @since 2.2.0

      */

     private VariableResolverFactory variableResolverFactory;

     /**

      * Constructor.

      *

      * @param requestHolder The object that holds the Tiles request context of

      * the current thread.

      * @param variableResolverFactory The resolver factory to use.

      * @since 2.2.0

      */

     public MVELAttributeEvaluator(TilesRequestContextHolder requestHolder,

             VariableResolverFactory variableResolverFactory) {

         this.requestHolder = requestHolder;

         this.variableResolverFactory = variableResolverFactory;

     }

     /** {@inheritDoc} */

     public Object evaluate(String expression, Request request) {

         if (expression == null) {

             throw new IllegalArgumentException("The expression parameter cannot be null");

         }

         requestHolder.setTilesRequestContext(request);

         return MVEL.eval(expression, variableResolverFactory);

     }

 }