Add a first cut of an abstractFacade task. This is supposed to be the base class of the Jspc, Javac, Rmic and similar facade tasks

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271839 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/myrmidon/framework/AbstractFacadeTask.java

@@ -0,0 +1,187 @@
+/*
+ * Copyright (C) The Apache Software Foundation. All rights reserved.
+ *
+ * This software is published under the terms of the Apache Software License
+ * version 1.1, a copy of which has been included with this distribution in
+ * the LICENSE.txt file.
+ */
+package org.apache.myrmidon.framework;
+
+import org.apache.avalon.excalibur.i18n.ResourceManager;
+import org.apache.avalon.excalibur.i18n.Resources;
+import org.apache.avalon.framework.configuration.Configurable;
+import org.apache.avalon.framework.configuration.Configuration;
+import org.apache.avalon.framework.configuration.ConfigurationException;
+import org.apache.avalon.framework.configuration.DefaultConfiguration;
+import org.apache.myrmidon.api.TaskException;
+
+/**
+ * Abstract task used to write tasks that delegate to facades
+ * such as Javac, Jspc and so forth.
+ *
+ * @author <a href="mailto:peter@apache.org">Peter Donald</a>
+ * @version $Revision$ $Date$
+ */
+public abstract class AbstractFacadeTask
+    extends AbstractContainerTask
+    implements Configurable
+{
+    private final static Resources REZ =
+        ResourceManager.getPackageResources( AbstractFacadeTask.class );
+
+    /**
+     * The name of the attribute used to select specific
+     * implementation of facade.
+     */
+    private final String m_selector;
+
+    /**
+     * The Class type for the facade (also used as the role
+     * when looking up TypeManager).
+     */
+    private final Class m_facadeType;
+
+    /**
+     * The default name of implementation if none are specified.
+     */
+    private final String m_defaultName;
+
+    /**
+     * The configuration used to configure the facade implementation.
+     */
+    private Configuration m_configuration;
+
+    /**
+     * Create the facade task that works with specified facade class,
+     * using the selector attribute to find implementation or using
+     * defaultName if selector attribute not specified.
+     */
+    protected AbstractFacadeTask( final String selector,
+                                  final Class facadeType,
+                                  final String defaultName )
+    {
+        m_selector = selector;
+        m_facadeType = facadeType;
+        m_defaultName = defaultName;
+    }
+
+    /**
+     * Supply the configuration for this task.
+     */
+    public void configure( final Configuration configuration )
+        throws ConfigurationException
+    {
+        m_configuration = configuration;
+    }
+
+    /**
+     * Utility method to create and configure the facade
+     * implementation.
+     */
+    protected Object prepareFacade()
+        throws TaskException
+    {
+        final Object facade = createFacade();
+        configureFacade( facade );
+        return facade;
+    }
+
+    /**
+     * Utility method to configure the specified facade.
+     * It will be configured according to normal resolution
+     * rules using the configuration data supplied to task
+     * minus the selector attribute if present.
+     */
+    protected void configureFacade( final Object facade )
+        throws TaskException
+    {
+        Configuration configuration = m_configuration;
+
+        if( null != m_selector &&
+            null != m_configuration.getAttribute( m_selector, null ) )
+        {
+            configuration = rebuildConfiguration( m_configuration, m_selector );
+        }
+
+        try
+        {
+            configureElement( facade, m_facadeType, configuration );
+        }
+        catch( final ConfigurationException ce )
+        {
+            throw new TaskException( ce.getMessage(), ce );
+        }
+    }
+
+    /**
+     * Rebuild the configuration tree with the attribute with specified
+     * name removed from top-level element.
+     */
+    private Configuration rebuildConfiguration( final Configuration configuration,
+                                                final String attribute )
+    {
+        final DefaultConfiguration newConfiguration =
+            new DefaultConfiguration( configuration.getName(),
+                                      configuration.getLocation() );
+
+        //Add all the attributes from old configuration except the one
+        //that was used to select the particular implementation
+        final String[] names = configuration.getAttributeNames();
+        for( int i = 0; i < names.length; i++ )
+        {
+            final String name = names[ i ];
+            if( !name.equals( attribute ) )
+            {
+                final String value = configuration.getAttribute( name, null );
+                newConfiguration.setAttribute( name, value );
+            }
+        }
+
+        //Add all elements to new configuration element in the
+        //correct order
+        final Configuration[] children = configuration.getChildren();
+        for( int i = 0; i < children.length; i++ )
+        {
+            newConfiguration.addChild( children[ i ] );
+        }
+
+        return newConfiguration;
+    }
+
+    /**
+     * Create the instance of the facade. It looks up the name
+     * of the implementation via the <code>getImplementation()</code>
+     * method and then creates a new instance from a TypeFactory
+     * using that name and the facadeType (specified in the
+     * constructor).
+     */
+    protected Object createFacade()
+        throws TaskException
+    {
+        final String implementation = getImplementation();
+        if( null == implementation )
+        {
+            final String message =
+                REZ.getString( "facade.missing-impl.error", getContext().getName() );
+            throw new TaskException( message );
+        }
+        return newInstance( m_facadeType, implementation );
+    }
+
+    /**
+     * Get the shortname of the implementation
+     * to use. It assumes that the implementation is registered in
+     * the TypeFactory under this shortname.
+     */
+    protected String getImplementation()
+    {
+        if( null != m_selector )
+        {
+            return m_configuration.getAttribute( m_selector, m_defaultName );
+        }
+        else
+        {
+            return m_defaultName;
+        }
+    }
+}

proposal/myrmidon/src/java/org/apache/myrmidon/framework/Resources.properties

@@ -14,3 +14,5 @@ type.no-create.error=Unable to create datatype.
 type.no-id.error=Id must be specified.
 
 unknown-family=Don't know how to detect os family "{0}"
+
+facade.missing-impl.error=Unable to determine the name of implementation for facade task "{0}".