constructorutils.java

APACHE 公司出的java bean 工具包

/*
 * 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.beanutils;

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

/**
 * <p> Utility reflection methods focussed on constructors, modelled after {@link MethodUtils}. </p>
 *
 * <h3>Known Limitations</h3>
 * <h4>Accessing Public Constructors In A Default Access Superclass</h4>
 * <p>There is an issue when invoking public constructors contained in a default access superclass.
 * Reflection locates these constructors fine and correctly assigns them as public.
 * However, an <code>IllegalAccessException</code> is thrown if the constructors is invoked.</p>
 *
 * <p><code>ConstructorUtils</code> contains a workaround for this situation.
 * It will attempt to call <code>setAccessible</code> on this constructor.
 * If this call succeeds, then the method can be invoked as normal.
 * This call will only succeed when the application has sufficient security privilages.
 * If this call fails then a warning will be logged and the method may fail.</p>
 *
 * @author Craig R. McClanahan
 * @author Ralph Schaer
 * @author Chris Audley
 * @author Rey Francois
 * @author Gregor Rayman
 * @author Jan Sorensen
 * @author Robert Burrell Donkin
 * @author Rodney Waldhoff
 * @version $Revision: 555824 $ $Date: 2007-07-13 01:27:15 +0100 (Fri, 13 Jul 2007) $
 */
public class ConstructorUtils {

    // --------------------------------------------------------- Private Members
    /** An empty class array */
    private static final Class[] EMPTY_CLASS_PARAMETERS = new Class[0];
    /** An empty object array */
    private static final Object[] EMPTY_OBJECT_ARRAY = new Object[0];

    // --------------------------------------------------------- Public Methods

    /**
     * <p>Convenience method returning new instance of <code>klazz</code> using a single argument constructor.
     * The formal parameter type is inferred from the actual values of <code>arg</code>.
     * See {@link #invokeExactConstructor(Class, Object[], Class[])} for more details.</p>
     *
     * <p>The signatures should be assignment compatible.</p>
     *
     * @param klass the class to be constructed.
     * @param arg the actual argument
     * @return new instance of <code>klazz</code>
     *
     * @throws NoSuchMethodException If the constructor cannot be found
     * @throws IllegalAccessException If an error occurs accessing the constructor
     * @throws InvocationTargetException If an error occurs invoking the constructor
     * @throws InstantiationException If an error occurs instantiating the class
     *
     * @see #invokeConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
     */
    public static Object invokeConstructor(Class klass, Object arg)
        throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException,
            InstantiationException {

        Object[] args = { arg };
        return invokeConstructor(klass, args);

    }

    /**
     * <p>Returns new instance of <code>klazz</code> created using the actual arguments <code>args</code>.
     * The formal parameter types are inferred from the actual values of <code>args</code>.
     * See {@link #invokeExactConstructor(Class, Object[], Class[])} for more details.</p>
     *
     * <p>The signatures should be assignment compatible.</p>
     *
     * @param klass the class to be constructed.
     * @param args actual argument array
     * @return new instance of <code>klazz</code>
     *
     * @throws NoSuchMethodException If the constructor cannot be found
     * @throws IllegalAccessException If an error occurs accessing the constructor
     * @throws InvocationTargetException If an error occurs invoking the constructor
     * @throws InstantiationException If an error occurs instantiating the class
     *
     * @see #invokeConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
     */
    public static Object invokeConstructor(Class klass, Object[] args)
        throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException,
            InstantiationException {

        if (null == args) {
            args = EMPTY_OBJECT_ARRAY;
        }
        int arguments = args.length;
        Class parameterTypes[] = new Class[arguments];
        for (int i = 0; i < arguments; i++) {
            parameterTypes[i] = args[i].getClass();
        }
        return invokeConstructor(klass, args, parameterTypes);

    }

    /**
     * <p>Returns new instance of <code>klazz</code> created using constructor
     * with signature <code>parameterTypes</code> and actual arguments <code>args</code>.</p>
     *
     * <p>The signatures should be assignment compatible.</p>
     *
     * @param klass the class to be constructed.
     * @param args actual argument array
     * @param parameterTypes parameter types array
     * @return new instance of <code>klazz</code>
     *
     * @throws NoSuchMethodException if matching constructor cannot be found
     * @throws IllegalAccessException thrown on the constructor's invocation
     * @throws InvocationTargetException thrown on the constructor's invocation
     * @throws InstantiationException thrown on the constructor's invocation
     * @see Constructor#newInstance
     */
    public static Object invokeConstructor(
        Class klass,
        Object[] args,
        Class[] parameterTypes)
        throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException,
            InstantiationException {

        if (parameterTypes == null) {
            parameterTypes = EMPTY_CLASS_PARAMETERS;
        }
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }

        Constructor ctor =
            getMatchingAccessibleConstructor(klass, parameterTypes);
        if (null == ctor) {
            throw new NoSuchMethodException(
                "No such accessible constructor on object: " + klass.getName());
        }
        return ctor.newInstance(args);
    }


    /**
     * <p>Convenience method returning new instance of <code>klazz</code> using a single argument constructor.
     * The formal parameter type is inferred from the actual values of <code>arg</code>.
     * See {@link #invokeExactConstructor(Class, Object[], Class[])} for more details.</p>
     *
     * <p>The signatures should match exactly.</p>
     *
     * @param klass the class to be constructed.
     * @param arg the actual argument
     * @return new instance of <code>klazz</code>
     *
     * @throws NoSuchMethodException If the constructor cannot be found
     * @throws IllegalAccessException If an error occurs accessing the constructor
     * @throws InvocationTargetException If an error occurs invoking the constructor
     * @throws InstantiationException If an error occurs instantiating the class
     *
     * @see #invokeExactConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
     */
    public static Object invokeExactConstructor(Class klass, Object arg)
        throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException,
            InstantiationException {

        Object[] args = { arg };
        return invokeExactConstructor(klass, args);

    }

    /**
     * <p>Returns new instance of <code>klazz</code> created using the actual arguments <code>args</code>.
     * The formal parameter types are inferred from the actual values of <code>args</code>.
     * See {@link #invokeExactConstructor(Class, Object[], Class[])} for more details.</p>
     *
     * <p>The signatures should match exactly.</p>
     *
     * @param klass the class to be constructed.
     * @param args actual argument array
     * @return new instance of <code>klazz</code>
     *
     * @throws NoSuchMethodException If the constructor cannot be found
     * @throws IllegalAccessException If an error occurs accessing the constructor
     * @throws InvocationTargetException If an error occurs invoking the constructor
     * @throws InstantiationException If an error occurs instantiating the class
     *
     * @see #invokeExactConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
     */
    public static Object invokeExactConstructor(Class klass, Object[] args)
        throws