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MVELAttributeEvaluator xref
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1   /*
2    * $Id: MVELAttributeEvaluator.java 833737 2009-11-07 19:17:09Z 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  
22  package org.apache.tiles.mvel;
23  
24  import org.apache.tiles.context.TilesRequestContextHolder;
25  import org.apache.tiles.evaluator.AbstractAttributeEvaluator;
26  import org.apache.tiles.request.Request;
27  import org.mvel2.MVEL;
28  import org.mvel2.integration.VariableResolverFactory;
29  
30  /**
31   * Allows to use MVEL as the language to evaluate attribute values.
32   *
33   * @version $Rev: 833737 $ $Date: 2009-11-08 06:17:09 +1100 (Sun, 08 Nov 2009) $
34   * @since 2.2.0
35   */
36  public class MVELAttributeEvaluator extends AbstractAttributeEvaluator {
37  
38      /**
39       * Holds the Tiles request context of the current thread.
40       */
41      private TilesRequestContextHolder requestHolder;
42  
43      /**
44       * Resolves variables when starting from the root.
45       *
46       * @since 2.2.0
47       */
48      private VariableResolverFactory variableResolverFactory;
49  
50      /**
51       * Constructor.
52       *
53       * @param requestHolder The object that holds the Tiles request context of
54       * the current thread.
55       * @param variableResolverFactory The resolver factory to use.
56       * @since 2.2.0
57       */
58      public MVELAttributeEvaluator(TilesRequestContextHolder requestHolder,
59              VariableResolverFactory variableResolverFactory) {
60          this.requestHolder = requestHolder;
61          this.variableResolverFactory = variableResolverFactory;
62      }
63  
64      /** {@inheritDoc} */
65      public Object evaluate(String expression, Request request) {
66          if (expression == null) {
67              throw new IllegalArgumentException("The expression parameter cannot be null");
68          }
69          requestHolder.setTilesRequestContext(request);
70          return MVEL.eval(expression, variableResolverFactory);
71      }
72  }