Commons DBCP example source code file (ConstructorUtil.java)

This example Commons DBCP source code file (ConstructorUtil.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons DBCP tags/keywords

class, class, constructor, constructor, constructorutil, illegalaccessexception, instantiationexception, invocationtargetexception, invocationtargetexception, nullpointerexception, object, object, reflection

The Commons DBCP ConstructorUtil.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.jocl;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

/**
 * Miscellaneous {@link Constructor} related utility functions.
 *
 * @author Rodney Waldhoff
 * @version $Revision: 479137 $ $Date: 2006-11-25 10:51:48 -0500 (Sat, 25 Nov 2006) $
 */
public class ConstructorUtil {
    /**
     * Returns a {@link Constructor} for the given method signature, or <tt>null
     * if no such <tt>Constructor can be found.
     *
     * @param type     the (non-<tt>null) type of {@link Object} the returned {@link Constructor} should create
     * @param argTypes a non-<tt>null array of types describing the parameters to the {@link Constructor}.
     * @return a {@link Constructor} for the given method signature, or <tt>null
     *         if no such <tt>Constructor can be found.
     * @see #invokeConstructor
     */
    public static Constructor getConstructor(Class type, Class[] argTypes) {
        if(null == type || null == argTypes) {
            throw new NullPointerException();
        }
        Constructor ctor = null;
        try {
            ctor = type.getConstructor(argTypes);
        } catch(Exception e) {
            ctor = null;
        }
        if(null == ctor) {
            // no directly declared matching constructor,
            // look for something that will work
            // XXX this should really be more careful to
            //     adhere to the jls mechanism for late binding
            Constructor[] ctors = type.getConstructors();
            for(int i=0;i<ctors.length;i++) {
                Class[] paramtypes = ctors[i].getParameterTypes();
                if(paramtypes.length == argTypes.length) {
                    boolean canuse = true;
                    for(int j=0;j<paramtypes.length;j++) {
                        if(paramtypes[j].isAssignableFrom(argTypes[j])) {
                            continue;
                        } else {
                            canuse = false;
                            break;
                        }
                    }
                    if(canuse == true) {
                        ctor = ctors[i];
                        break;
                    }
                }
            }
        }
        return ctor;
    }

    /**
     * Creates a new instance of the specified <tt>type
     * using a {@link Constructor} described by the given parameter types
     * and values.
     *
     * @param type      the type of {@link Object} to be created
     * @param argTypes  a non-<tt>null array of types describing the parameters to the {@link Constructor}.
     * @param argValues a non-<tt>null array containing the values of the parameters to the {@link Constructor}.
     * @return a new instance of the specified <tt>type
     *         using a {@link Constructor} described by the given parameter types
     *         and values.
     * @exception InstantiationException
     * @exception IllegalAccessException
     * @exception InvocationTargetException
     */
    public static Object invokeConstructor(Class type, Class[] argTypes, Object[] argValues) throws InstantiationException, IllegalAccessException, InvocationTargetException {
        return ConstructorUtil.getConstructor(type,argTypes).newInstance(argValues);
    }
}