001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.jxpath.functions;
018
019 import java.lang.reflect.Constructor;
020 import java.lang.reflect.InvocationTargetException;
021
022 import org.apache.commons.jxpath.ExpressionContext;
023 import org.apache.commons.jxpath.Function;
024 import org.apache.commons.jxpath.JXPathInvalidAccessException;
025 import org.apache.commons.jxpath.util.TypeUtils;
026
027 /**
028 * An extension function that creates an instance using a constructor.
029 *
030 * @author Dmitri Plotnikov
031 * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
032 */
033 public class ConstructorFunction implements Function {
034 private static final Object[] EMPTY_ARRAY = new Object[0];
035
036 private Constructor constructor;
037
038 /**
039 * Create a new ConstructorFunction.
040 * @param constructor the constructor to call.
041 */
042 public ConstructorFunction(Constructor constructor) {
043 this.constructor = constructor;
044 }
045
046 /**
047 * Converts parameters to suitable types and invokes the constructor.
048 * @param context evaluation context
049 * @param parameters constructor args
050 * @return new instance
051 */
052 public Object invoke(ExpressionContext context, Object[] parameters) {
053 try {
054 Object[] args;
055 if (parameters == null) {
056 parameters = EMPTY_ARRAY;
057 }
058 int pi = 0;
059 Class[] types = constructor.getParameterTypes();
060 if (types.length > 0
061 && ExpressionContext.class.isAssignableFrom(types[0])) {
062 pi = 1;
063 }
064 args = new Object[parameters.length + pi];
065 if (pi == 1) {
066 args[0] = context;
067 }
068 for (int i = 0; i < parameters.length; i++) {
069 args[i + pi] = TypeUtils.convert(parameters[i], types[i + pi]);
070 }
071 return constructor.newInstance(args);
072 }
073 catch (Throwable ex) {
074 if (ex instanceof InvocationTargetException) {
075 ex = ((InvocationTargetException) ex).getTargetException();
076 }
077 throw new JXPathInvalidAccessException(
078 "Cannot invoke constructor " + constructor,
079 ex);
080 }
081 }
082 }