trunk/proposal/embed/src/java/org/apache/tools/ant/ProjectComponentHelper.java

/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000-2002 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 acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Ant", 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 apache@apache.org.
 *
 * 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 Group.
 *
 * 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
 * <http://www.apache.org/>.
 */

package org.apache.tools.ant;

import java.io.File;
import java.io.InputStream;
import java.io.IOException;
import java.util.Hashtable;
import java.util.Vector;
import java.util.Properties;
import java.util.Enumeration;
import java.util.Stack;
import java.lang.reflect.Modifier;


import org.apache.tools.ant.types.FilterSet; 
import org.apache.tools.ant.types.FilterSetCollection; 
import org.apache.tools.ant.util.FileUtils; 

/** 
 * Component creation and configuration.
 *
 * After a ProjectComponentFactory is registered, it'll manage the construction and 
 * configuration of tasks/types/etc. It has full control over how the
 * component is created - and may provide runtime wrapping for components
 * not implementing the Task/DataType interfaces.
 * It works in close relation with TaskAdapter and RuntimeConfigurable
 * to handle delayed evaluation of tasks or custom attribute-&gt;task mapping.
 * If it returns a wrapper for Task, the wrapper is required to extend
 * TaskAdapter.
 *
 * The common 'Chain' pattern is used to construct
 * tasks, with the original behavior ( Class registry ) tried last, by the
 * default helper implementation.
 *
 * Note that 'delayed' construction of tasks is used.
 *
 */
public class ProjectComponentHelper  {
    static private ProjectComponentHelper singleton=new ProjectComponentHelper();
    
    Vector factories=new Vector();

    /**
     */
    public static ProjectComponentHelper getProjectComponentHelper() {
        // Singleton for now, it may change ( per/classloader )
        return singleton;
    }

    public void addComponentFactory( ProjectComponentFactory fact ) {
        factories.addElement( fact );
    }
    
    public Object createProjectComponent( UnknownElement ue, Project project,
                                          String ns,
                                          String taskName )
        throws BuildException
    {
        Object component=null;
        for( int i=0; i< factories.size(); i++ ) {
            ProjectComponentFactory fact=(ProjectComponentFactory)factories.elementAt(i);
            component=fact.createProjectComponent( project, ns, taskName );
            if( component!=null ) return component;
        }

        // System.out.println("Fallback to project default " + taskName );
        // Can't create component. Default is to use the old methods in project.

        // This policy is taken from 1.5 ProjectHelper. In future the difference between
        // task and type should disapear.
        if( project.getDataTypeDefinitions().get(taskName) != null ) {
            // This is the original policy in ProjectHelper. The 1.5 version of UnkwnonwElement
            // used to try first to create a task, and if it failed tried a type. In 1.6 the diff
            // should disapear.
            component = project.createDataType(taskName);
            if( component!=null ) return component;
        }

        // from UnkwnonwElement.createTask. The 'top level' case is removed, we're
        // allways lazy
        component = project.createTask(taskName);

        return component;
    }
}