org.apache.commons.collections.functors.InstantiateTransformer Maven / Gradle / Ivy

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001-2004 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * .
 */
package org.apache.commons.collections.functors;

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

import org.apache.commons.collections.FunctorException;
import org.apache.commons.collections.Transformer;

/**
 * Transformer implementation that creates a new object instance by reflection.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 1.4 $ $Date: 2004/01/14 21:43:09 $
 *
 * @author Stephen Colebourne
 */
public class InstantiateTransformer implements Transformer, Serializable {

    /** The serial version */
    static final long serialVersionUID = 3786388740793356347L;
    
    /** Singleton instance that uses the no arg constructor */
    public static final Transformer NO_ARG_INSTANCE = new InstantiateTransformer();

    /** The constructor parameter types */
    private final Class[] iParamTypes;
    /** The constructor arguments */
    private final Object[] iArgs;

    /**
     * Transformer method that performs validation.
     * 
     * @param paramTypes  the constructor parameter types
     * @param args  the constructor arguments
     */
    public static Transformer getInstance(Class[] paramTypes, Object[] args) {
        if (((paramTypes == null) && (args != null))
            || ((paramTypes != null) && (args == null))
            || ((paramTypes != null) && (args != null) && (paramTypes.length != args.length))) {
            throw new IllegalArgumentException("Parameter types must match the arguments");
        }

        if (paramTypes == null || paramTypes.length == 0) {
            return NO_ARG_INSTANCE;
        } else {
            paramTypes = (Class[]) paramTypes.clone();
            args = (Object[]) args.clone();
        }
        return new InstantiateTransformer(paramTypes, args);
    }

    /**
     * Constructor for no arg instance.
     */
    private InstantiateTransformer() {
        super();
        iParamTypes = null;
        iArgs = null;
    }

    /**
     * Constructor that performs no validation.
     * Use getInstance if you want that.
     * 
     * @param paramTypes  the constructor parameter types, not cloned
     * @param args  the constructor arguments, not cloned
     */
    public InstantiateTransformer(Class[] paramTypes, Object[] args) {
        super();
        iParamTypes = paramTypes;
        iArgs = args;
    }

    /**
     * Return the result of instantiating the input Class object.
     */
    public Object transform(Object input) {
        try {
            if (input instanceof Class == false) {
                throw new FunctorException(
                    "InstantiateTransformer: Input object was not an instanceof Class, it was a "
                        + (input == null ? "null object" : input.getClass().getName()));
            }
            Constructor con = ((Class) input).getConstructor(iParamTypes);
            return con.newInstance(iArgs);

        } catch (NoSuchMethodException ex) {
            throw new FunctorException("InstantiateTransformer: The constructor must exist and be public ");
        } catch (InstantiationException ex) {
            throw new FunctorException("InstantiateTransformer: InstantiationException", ex);
        } catch (IllegalAccessException ex) {
            throw new FunctorException("InstantiateTransformer: Constructor must be public", ex);
        } catch (InvocationTargetException ex) {
            throw new FunctorException("InstantiateTransformer: Constructor threw an exception", ex);
        }
    }
    
}