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1   /*
2    * Copyright 2002,2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.commons.jelly.tags.bsf;
17  
18  import org.apache.bsf.BSFEngine;
19  import org.apache.bsf.BSFManager;
20  
21  import java.util.Iterator;
22  
23  import org.apache.commons.jelly.JellyContext;
24  import org.apache.commons.jelly.expression.ExpressionSupport;
25  
26  import org.apache.commons.logging.Log;
27  import org.apache.commons.logging.LogFactory;
28  
29  
30  /*** Represents a BSF expression
31    *
32    * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
33    * @version $Revision: 155420 $
34    */
35  public class BSFExpression extends ExpressionSupport {
36  
37      /*** The Log to which logging calls will be made. */
38      private static final Log log = LogFactory.getLog( BSFExpression.class );
39  
40      /*** The expression */
41      private String text;
42  
43      /*** The BSF Engine to evaluate expressions */
44      private BSFEngine engine;
45      /*** The BSF Manager to evaluate expressions */
46      private BSFManager manager;
47  
48      /*** The adapter to BSF's ObjectRegistry that uses the JellyContext */
49      private JellyContextRegistry registry;
50  
51      public BSFExpression(String text, BSFEngine engine, BSFManager manager, JellyContextRegistry registry) {
52          this.text = text;
53          this.engine = engine;
54          this.manager = manager;
55          this.registry = registry;
56      }
57  
58      // Expression interface
59      //-------------------------------------------------------------------------
60      public String getExpressionText() {
61          return "${" + text + "}";
62      }
63  
64      public Object evaluate(JellyContext context) {
65          // XXXX: unfortunately we must sychronize evaluations
66          // so that we can swizzle in the context.
67          // maybe we could create an expression from a context
68          // (and so create a BSFManager for a context)
69          synchronized (registry) {
70              registry.setJellyContext(context);
71  
72              try {
73                  // XXXX: hack - there must be a better way!!!
74                  for ( Iterator iter = context.getVariableNames(); iter.hasNext(); ) {
75                      String name = (String) iter.next();
76                      Object value = context.getVariable( name );
77                      manager.declareBean( name, value, value.getClass() );
78                  }
79                  return engine.eval( text, -1, -1, text );
80              }
81              catch (Exception e) {
82                  log.warn( "Caught exception evaluating: " + text + ". Reason: " + e, e );
83                  return null;
84              }
85          }
86      }
87  }