/*
    * $Id: JspExpressionFactoryFactory.java 1229087 2012-01-09 10:35:14Z mck $
    *
    * 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.ExpressionFactory;
  import javax.servlet.ServletContext;
  import javax.servlet.jsp.JspFactory;
  
  import org.apache.tiles.request.ApplicationContext;
  import org.apache.tiles.request.ApplicationContextAware;
  
  /**
   * Uses the JSP 2.1 {@link ExpressionFactory} to be used in Tiles.
   *
   * @version $Rev: 1229087 $ $Date: 2012-01-09 21:35:14 +1100 (Mon, 09 Jan 2012) $
   * @since 2.2.1
   */
  public class JspExpressionFactoryFactory implements ExpressionFactoryFactory,
          ApplicationContextAware {
  
      /**
       * The servlet context.
       *
       * @since 2.2.1
       */
      protected ServletContext servletContext;
  
      /** {@inheritDoc} */
      public void setApplicationContext(ApplicationContext applicationContext) {
          Object context = applicationContext.getContext();
          if (context instanceof ServletContext) {
              this.servletContext = (ServletContext) context;
          } else {
              throw new IllegalArgumentException(
                      "The application context does not hold an instance of "
                      + "ServletContext, consider using JuelExpressionFactoryFactory");
          }
      }
  
      /** {@inheritDoc} */
      public ExpressionFactory getExpressionFactory() {
          return JspFactory.getDefaultFactory().getJspApplicationContext(
                  servletContext).getExpressionFactory();
      }
  }