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 package org.apache.commons.jxpath.functions;
18
19 import java.lang.reflect.Constructor;
20 import java.lang.reflect.InvocationTargetException;
21
22 import org.apache.commons.jxpath.ExpressionContext;
23 import org.apache.commons.jxpath.Function;
24 import org.apache.commons.jxpath.JXPathInvalidAccessException;
25 import org.apache.commons.jxpath.util.TypeUtils;
26
27 /**
28 * An extension function that creates an instance using a constructor.
29 *
30 * @author Dmitri Plotnikov
31 * @version $Revision: 652845 $ $Date: 2008-05-02 19:46:46 +0200 (Fr, 02 Mai 2008) $
32 */
33 public class ConstructorFunction implements Function {
34 private static final Object[] EMPTY_ARRAY = new Object[0];
35
36 private Constructor constructor;
37
38 /**
39 * Create a new ConstructorFunction.
40 * @param constructor the constructor to call.
41 */
42 public ConstructorFunction(Constructor constructor) {
43 this.constructor = constructor;
44 }
45
46 /**
47 * Converts parameters to suitable types and invokes the constructor.
48 * @param context evaluation context
49 * @param parameters constructor args
50 * @return new instance
51 */
52 public Object invoke(ExpressionContext context, Object[] parameters) {
53 try {
54 Object[] args;
55 if (parameters == null) {
56 parameters = EMPTY_ARRAY;
57 }
58 int pi = 0;
59 Class[] types = constructor.getParameterTypes();
60 if (types.length > 0
61 && ExpressionContext.class.isAssignableFrom(types[0])) {
62 pi = 1;
63 }
64 args = new Object[parameters.length + pi];
65 if (pi == 1) {
66 args[0] = context;
67 }
68 for (int i = 0; i < parameters.length; i++) {
69 args[i + pi] = TypeUtils.convert(parameters[i], types[i + pi]);
70 }
71 return constructor.newInstance(args);
72 }
73 catch (Throwable ex) {
74 if (ex instanceof InvocationTargetException) {
75 ex = ((InvocationTargetException) ex).getTargetException();
76 }
77 throw new JXPathInvalidAccessException(
78 "Cannot invoke constructor " + constructor,
79 ex);
80 }
81 }
82 }