Added the proposed hook for component creation.

Full backward compatibility is provided - the project
is used to create tasks. The mechanism allows full
flexibility in implementing any kind of antlib policy,
and allows applications embeding ant to integrate in the
component creation process.

Probably a good improvement would be to move the 'default'
behavior in a separate plugin ( DefaultComponentFactory - to
use the project component storage ), and deprecate the use
of Project for project component management.

After more feedback is received I'll propose this for the
main branch.


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@273430 13f79535-47bb-0310-9956-ffa450edef68

proposal/embed/src/java/org/apache/tools/ant/ProjectComponentFactory.java

@@ -0,0 +1,117 @@
+/*
+ * 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; 
+
+// XXX It would be a good idea to merge all 'hooks' into one AntInterceptor
+// mechanism. That would make it much easier to read and extend.
+
+/** 
+ * Abstract component creation and configuration.
+ *
+ * TODO: Multiple ComponentHelpers can be registered in a project, either by an
+ * embedding application or by taskdef-like tasks.
+ *
+ * After a ProjectComponentHelper 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->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.
+ *
+ * @author Costin Manolache
+ */
+public interface ProjectComponentFactory {
+
+    /** Creates an ant component..
+     *
+     * A factory may have knowledge about the tasks it creates. It can return
+     * an object extending TaskAdapter that emulates Task/DataType. If null is returned,
+     * the next helper is tried.
+     *
+     * @param project the context for task creation.
+     * @param role Class name for the expected role ( Task, Type, Filter, etc ). Null for 'any'
+     * @param ns namespace if a SAX2 parser is used, null for 'classical' ant
+     * @param taskName the (local) name of the task.
+     */
+    public Object createProjectComponent( Project project,
+                                          String ns,
+                                          String taskName )
+        throws BuildException;
+    // XXX class loader ? Can use the ns, but additional hints may be available in taskdef
+    // 
+}

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

@@ -0,0 +1,139 @@
+/*
+ * 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->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.
+ *
+ * @author Costin Manolache
+ */
+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;
+    }
+}