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1   /*
2    * $Id: ELAttributeEvaluator.java 891884 2009-12-17 20:43:12Z apetrelli $
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   * http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  package org.apache.tiles.el;
22  
23  import javax.el.ELResolver;
24  import javax.el.ExpressionFactory;
25  import javax.el.ValueExpression;
26  
27  import org.apache.tiles.evaluator.AbstractAttributeEvaluator;
28  import org.apache.tiles.request.ApplicationContext;
29  import org.apache.tiles.request.Request;
30  
31  /**
32   * Evaluates string expression with typical EL syntax.<br>
33   * You can use normal EL syntax, knowing that the root objects are
34   * {@link Request}, {@link ApplicationContext} and beans
35   * contained in request, session and application scope.
36   *
37   * @version $Rev: 891884 $ $Date: 2009-12-18 07:43:12 +1100 (Fri, 18 Dec 2009) $
38   * @since 2.2.1
39   */
40  public class ELAttributeEvaluator extends AbstractAttributeEvaluator {
41  
42      /**
43       * Initialization parameter to decide the implementation of
44       * {@link ExpressionFactoryFactory}.
45       *
46       * @since 2.2.1
47       */
48      public static final String EXPRESSION_FACTORY_FACTORY_INIT_PARAM =
49          "org.apache.tiles.evaluator.el.ExpressionFactoryFactory";
50  
51      /**
52       * The EL expression factory.
53       *
54       * @since 2.2.1
55       */
56      protected ExpressionFactory expressionFactory;
57  
58      /**
59       * The EL resolver to use.
60       *
61       * @since 2.2.1
62       */
63      protected ELResolver resolver;
64  
65      /**
66       * Constructor.
67       *
68       * @since 2.2.1
69       */
70      public ELAttributeEvaluator() {
71      }
72  
73      /**
74       * Sets the expression factory to use.
75       *
76       * @param expressionFactory The expression factory.
77       * @since 2.2.1
78       */
79      public void setExpressionFactory(ExpressionFactory expressionFactory) {
80          this.expressionFactory = expressionFactory;
81      }
82  
83      /**
84       * Sets the EL resolver to use.
85       *
86       * @param resolver The EL resolver.
87       * @since 2.2.1
88       */
89      public void setResolver(ELResolver resolver) {
90          this.resolver = resolver;
91      }
92  
93      /** {@inheritDoc} */
94      public Object evaluate(String expression, Request request) {
95          ELContextImpl context = new ELContextImpl(resolver);
96          context.putContext(Request.class, request);
97          context.putContext(ApplicationContext.class,
98                  request.getApplicationContext());
99          ValueExpression valueExpression = expressionFactory
100                 .createValueExpression(context, expression, Object.class);
101 
102         return valueExpression.getValue(context);
103     }
104 }