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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.proxy.invoker;
19  
20  import org.apache.commons.proxy.Invoker;
21  
22  import java.lang.reflect.Method;
23  import java.util.HashMap;
24  import java.util.Map;
25  
26  /**
27   * An {@link Invoker} implementation which merely returns null for all method invocations.  This class is
28   * useful for scenarios where the "null object" design pattern is needed.
29   *
30   * @author James Carman
31   * @since 1.0
32   */
33  public class NullInvoker implements Invoker
34  {
35      private static Map primitiveValueMap = new HashMap();
36      static
37      {
38          primitiveValueMap.put( Integer.TYPE, new Integer( 0 ) );
39          primitiveValueMap.put( Long.TYPE, new Long( 0 ) );
40          primitiveValueMap.put( Short.TYPE, new Short( ( short )0 ) );
41          primitiveValueMap.put( Byte.TYPE, new Byte( ( byte )0 ) );
42          primitiveValueMap.put( Float.TYPE, new Float( 0.0f ) );
43          primitiveValueMap.put( Double.TYPE, new Double( 0.0 ) );
44          primitiveValueMap.put( Character.TYPE, new Character( ( char )0 ) );
45          primitiveValueMap.put( Boolean.TYPE, Boolean.FALSE );
46      }
47  //----------------------------------------------------------------------------------------------------------------------
48  // InvocationHandler Implementation
49  //----------------------------------------------------------------------------------------------------------------------
50  
51      public Object invoke( Object proxy, Method method, Object[] args ) throws Throwable
52      {
53          final Class returnType = method.getReturnType();
54          if( returnType.isPrimitive() )
55          {
56              return primitiveValueMap.get( returnType );
57          }
58          else
59          {
60              return null;
61          }
62      }
63  }
64