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1   package org.apache.velocity.runtime.parser.node;
2   
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  import java.lang.reflect.InvocationTargetException;
23  
24  import org.apache.velocity.runtime.RuntimeLogger;
25  import org.apache.velocity.runtime.log.Log;
26  import org.apache.velocity.runtime.log.RuntimeLoggerLog;
27  import org.apache.velocity.util.introspection.Introspector;
28  
29  
30  /**
31   * Executor that simply tries to execute a get(key)
32   * operation. This will try to find a get(key) method
33   * for any type of object, not just objects that
34   * implement the Map interface as was previously
35   * the case.
36   *
37   * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
38   * @version $Id: GetExecutor.java 463298 2006-10-12 16:10:32Z henning $
39   */
40  public class GetExecutor extends AbstractExecutor
41  {
42      private final Introspector introspector;
43  
44      // This is still threadsafe because this object is only read except in the C'tor.
45      private Object [] params = {};
46  
47      /**
48       * @param log
49       * @param introspector
50       * @param clazz
51       * @param property
52       */
53      public GetExecutor(final Log log, final Introspector introspector,
54              final Class clazz, final String property)
55      {
56          this.log = log;
57          this.introspector = introspector;
58  
59          // If you passed in null as property, we don't use the value
60          // for parameter lookup. Instead we just look for get() without
61          // any parameters.
62          //
63          // In any other case, the following condition will set up an array
64          // for looking up get(String) on the class.
65  
66          if (property != null)
67          {
68              this.params = new Object[] { property };
69          }
70          discover(clazz);
71      }
72  
73      /**
74       * @param rlog
75       * @param introspector
76       * @param clazz
77       * @param property
78       * @deprecated RuntimeLogger is deprecated. Use the other constructor.
79       */
80      public GetExecutor(final RuntimeLogger rlog, final Introspector introspector,
81              final Class clazz, final String property)
82      {
83          this(new RuntimeLoggerLog(rlog), introspector, clazz, property);
84      }
85  
86      protected void discover(final Class clazz)
87      {
88          try
89          {
90              setMethod(introspector.getMethod(clazz, "get", params));
91          }
92          /**
93           * pass through application level runtime exceptions
94           */
95          catch( RuntimeException e )
96          {
97              throw e;
98          }
99          catch(Exception e)
100         {
101             log.error("While looking for get('" + params[0] + "') method:", e);
102         }
103     }
104 
105     /**
106      * @see org.apache.velocity.runtime.parser.node.AbstractExecutor#execute(java.lang.Object)
107      */
108     public Object execute(final Object o)
109         throws IllegalAccessException,  InvocationTargetException
110     {
111         return isAlive() ? getMethod().invoke(o, params) : null;
112     }
113 }