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    
018    package org.apache.commons.jocl;
019    
020    import java.lang.reflect.Constructor;
021    import java.lang.reflect.InvocationTargetException;
022    
023    /**
024     * Miscellaneous {@link Constructor} related utility functions.
025     *
026     * @author Rodney Waldhoff
027     * @version $Revision: 479137 $ $Date: 2006-11-25 10:51:48 -0500 (Sat, 25 Nov 2006) $
028     */
029    public class ConstructorUtil {
030        /**
031         * Returns a {@link Constructor} for the given method signature, or <tt>null</tt>
032         * if no such <tt>Constructor</tt> can be found.
033         *
034         * @param type     the (non-<tt>null</tt>) type of {@link Object} the returned {@link Constructor} should create
035         * @param argTypes a non-<tt>null</tt> array of types describing the parameters to the {@link Constructor}.
036         * @return a {@link Constructor} for the given method signature, or <tt>null</tt>
037         *         if no such <tt>Constructor</tt> can be found.
038         * @see #invokeConstructor
039         */
040        public static Constructor getConstructor(Class type, Class[] argTypes) {
041            if(null == type || null == argTypes) {
042                throw new NullPointerException();
043            }
044            Constructor ctor = null;
045            try {
046                ctor = type.getConstructor(argTypes);
047            } catch(Exception e) {
048                ctor = null;
049            }
050            if(null == ctor) {
051                // no directly declared matching constructor,
052                // look for something that will work
053                // XXX this should really be more careful to
054                //     adhere to the jls mechanism for late binding
055                Constructor[] ctors = type.getConstructors();
056                for(int i=0;i<ctors.length;i++) {
057                    Class[] paramtypes = ctors[i].getParameterTypes();
058                    if(paramtypes.length == argTypes.length) {
059                        boolean canuse = true;
060                        for(int j=0;j<paramtypes.length;j++) {
061                            if(paramtypes[j].isAssignableFrom(argTypes[j])) {
062                                continue;
063                            } else {
064                                canuse = false;
065                                break;
066                            }
067                        }
068                        if(canuse == true) {
069                            ctor = ctors[i];
070                            break;
071                        }
072                    }
073                }
074            }
075            return ctor;
076        }
077    
078        /**
079         * Creates a new instance of the specified <tt><i>type</i></tt>
080         * using a {@link Constructor} described by the given parameter types
081         * and values.
082         *
083         * @param type      the type of {@link Object} to be created
084         * @param argTypes  a non-<tt>null</tt> array of types describing the parameters to the {@link Constructor}.
085         * @param argValues a non-<tt>null</tt> array containing the values of the parameters to the {@link Constructor}.
086         * @return a new instance of the specified <tt><i>type</i></tt>
087         *         using a {@link Constructor} described by the given parameter types
088         *         and values.
089         * @exception InstantiationException
090         * @exception IllegalAccessException
091         * @exception InvocationTargetException
092         */
093        public static Object invokeConstructor(Class type, Class[] argTypes, Object[] argValues) throws InstantiationException, IllegalAccessException, InvocationTargetException {
094            return ConstructorUtil.getConstructor(type,argTypes).newInstance(argValues);
095        }
096    }
097    
098