/*

  * $Id: ELAttributeEvaluator.java 891884 2009-12-17 20:43:12Z 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.el;

 import javax.el.ELResolver;

 import javax.el.ExpressionFactory;

 import javax.el.ValueExpression;

 import org.apache.tiles.evaluator.AbstractAttributeEvaluator;

 import org.apache.tiles.request.ApplicationContext;

 import org.apache.tiles.request.Request;

 /**

  * Evaluates string expression with typical EL syntax.<br>

  * You can use normal EL syntax, knowing that the root objects are

  * {@link Request}, {@link ApplicationContext} and beans

  * contained in request, session and application scope.

  *

  * @version $Rev: 891884 $ $Date: 2009-12-18 07:43:12 +1100 (Fri, 18 Dec 2009) $

  * @since 2.2.1

  */

 public class ELAttributeEvaluator extends AbstractAttributeEvaluator {

     /**

      * Initialization parameter to decide the implementation of

      * {@link ExpressionFactoryFactory}.

      *

      * @since 2.2.1

      */

     public static final String EXPRESSION_FACTORY_FACTORY_INIT_PARAM =

         "org.apache.tiles.evaluator.el.ExpressionFactoryFactory";

     /**

      * The EL expression factory.

      *

      * @since 2.2.1

      */

     protected ExpressionFactory expressionFactory;

     /**

      * The EL resolver to use.

      *

      * @since 2.2.1

      */

     protected ELResolver resolver;

     /**

      * Constructor.

      *

      * @since 2.2.1

      */

     public ELAttributeEvaluator() {

     }

     /**

      * Sets the expression factory to use.

      *

      * @param expressionFactory The expression factory.

      * @since 2.2.1

      */

     public void setExpressionFactory(ExpressionFactory expressionFactory) {

         this.expressionFactory = expressionFactory;

     }

     /**

      * Sets the EL resolver to use.

      *

      * @param resolver The EL resolver.

      * @since 2.2.1

      */

     public void setResolver(ELResolver resolver) {

         this.resolver = resolver;

     }

     /** {@inheritDoc} */

     public Object evaluate(String expression, Request request) {

         ELContextImpl context = new ELContextImpl(resolver);

         context.putContext(Request.class, request);

         context.putContext(ApplicationContext.class,

                 request.getApplicationContext());

         ValueExpression valueExpression = expressionFactory

                 .createValueExpression(context, expression, Object.class);

         return valueExpression.getValue(context);

     }

 }