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1   /*
2    * Copyright 1999-2004 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.jxpath.functions;
17  
18  import java.lang.reflect.Constructor;
19  import java.lang.reflect.InvocationTargetException;
20  
21  import org.apache.commons.jxpath.ExpressionContext;
22  import org.apache.commons.jxpath.Function;
23  import org.apache.commons.jxpath.JXPathException;
24  import org.apache.commons.jxpath.util.TypeUtils;
25  
26  /***
27   * An extension function that creates an instance using a constructor.
28   *
29   * @author Dmitri Plotnikov
30   * @version $Revision: 1.11 $ $Date: 2004/02/29 14:17:44 $
31   */
32  public class ConstructorFunction implements Function {
33  
34      private Constructor constructor;
35      private static final Object EMPTY_ARRAY[] = new Object[0];
36  
37      public ConstructorFunction(Constructor constructor) {
38          this.constructor = constructor;
39      }
40  
41      /***
42       * Converts parameters to suitable types and invokes the constructor.
43       */
44      public Object invoke(ExpressionContext context, Object[] parameters) {
45          try {
46              Object[] args;
47              if (parameters == null) {
48                  parameters = EMPTY_ARRAY;
49              }
50              int pi = 0;
51              Class types[] = constructor.getParameterTypes();
52              if (types.length > 0
53                  && ExpressionContext.class.isAssignableFrom(types[0])) {
54                  pi = 1;
55              }
56              args = new Object[parameters.length + pi];
57              if (pi == 1) {
58                  args[0] = context;
59              }
60              for (int i = 0; i < parameters.length; i++) {
61                  args[i + pi] = TypeUtils.convert(parameters[i], types[i + pi]);
62              }
63              return constructor.newInstance(args);
64          }
65          catch (Throwable ex) {
66              if (ex instanceof InvocationTargetException) {
67                  ex = ((InvocationTargetException) ex).getTargetException();
68              }
69              throw new JXPathException(
70                  "Cannot invoke constructor " + constructor,
71                  ex);
72          }
73      }
74  }