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Commons Collections example source code file (FactoryUtils.java)

This example Commons Collections source code file (FactoryUtils.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 Collections tags/keywords

class, class, factory, factory, factoryutils, factoryutils, object, object

The Commons Collections FactoryUtils.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.collections;

import org.apache.commons.collections.functors.ConstantFactory;
import org.apache.commons.collections.functors.InstantiateFactory;
import org.apache.commons.collections.functors.ExceptionFactory;
import org.apache.commons.collections.functors.PrototypeFactory;

/**
 * <code>FactoryUtils provides reference implementations and utilities
 * for the Factory functor interface. The supplied factories are:
 * <ul>
 * <li>Prototype - clones a specified object
 * <li>Reflection - creates objects using reflection
 * <li>Constant - always returns the same object
 * <li>Null - always returns null
 * <li>Exception - always throws an exception
 * </ul>
 * All the supplied factories are Serializable.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 */
public class FactoryUtils {

    /**
     * This class is not normally instantiated.
     */
    public FactoryUtils() {
        super();
    }

    /**
     * Gets a Factory that always throws an exception.
     * This could be useful during testing as a placeholder.
     *
     * @see org.apache.commons.collections.functors.ExceptionFactory
     * 
     * @return the factory
     */
    public static Factory exceptionFactory() {
        return ExceptionFactory.INSTANCE;
    }

    /**
     * Gets a Factory that will return null each time the factory is used.
     * This could be useful during testing as a placeholder.
     *
     * @see org.apache.commons.collections.functors.ConstantFactory
     * 
     * @return the factory
     */
    public static Factory nullFactory() {
        return ConstantFactory.NULL_INSTANCE;
    }

    /**
     * Creates a Factory that will return the same object each time the factory
     * is used. No check is made that the object is immutable. In general, only
     * immutable objects should use the constant factory. Mutable objects should
     * use the prototype factory.
     *
     * @see org.apache.commons.collections.functors.ConstantFactory
     * 
     * @param constantToReturn  the constant object to return each time in the factory
     * @return the <code>constant factory.
     */
    public static Factory constantFactory(Object constantToReturn) {
        return ConstantFactory.getInstance(constantToReturn);
    }

    /**
     * Creates a Factory that will return a clone of the same prototype object
     * each time the factory is used. The prototype will be cloned using one of these
     * techniques (in order):
     * <ul>
     * <li>public clone method
     * <li>public copy constructor
     * <li>serialization clone
     * <ul>
     *
     * @see org.apache.commons.collections.functors.PrototypeFactory
     * 
     * @param prototype  the object to clone each time in the factory
     * @return the <code>prototype factory
     * @throws IllegalArgumentException if the prototype is null
     * @throws IllegalArgumentException if the prototype cannot be cloned
     */
    public static Factory prototypeFactory(Object prototype) {
        return PrototypeFactory.getInstance(prototype);
    }

    /**
     * Creates a Factory that can create objects of a specific type using
     * a no-args constructor.
     *
     * @see org.apache.commons.collections.functors.InstantiateFactory
     * 
     * @param classToInstantiate  the Class to instantiate each time in the factory
     * @return the <code>reflection factory
     * @throws IllegalArgumentException if the classToInstantiate is null
     */
    public static Factory instantiateFactory(Class classToInstantiate) {
        return InstantiateFactory.getInstance(classToInstantiate, null, null);
    }

    /**
     * Creates a Factory that can create objects of a specific type using
     * the arguments specified to this method.
     *
     * @see org.apache.commons.collections.functors.InstantiateFactory
     * 
     * @param classToInstantiate  the Class to instantiate each time in the factory
     * @param paramTypes  parameter types for the constructor, can be null
     * @param args  the arguments to pass to the constructor, can be null
     * @return the <code>reflection factory
     * @throws IllegalArgumentException if the classToInstantiate is null
     * @throws IllegalArgumentException if the paramTypes and args don't match
     * @throws IllegalArgumentException if the constructor doesn't exist
     */
    public static Factory instantiateFactory(Class classToInstantiate, Class[] paramTypes, Object[] args) {
        return InstantiateFactory.getInstance(classToInstantiate, paramTypes, args);
    }

}

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