/*
* Copyright 1999-2004 The Apache Software Foundation
*
* Licensed 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.chain.config;
import org.apache.commons.chain.Catalog;
import org.apache.commons.chain.CatalogFactory;
import org.apache.commons.digester.Rule;
import org.xml.sax.Attributes;
/**
* <p>Digester rule that will cause the top-most element on the Digester
* stack (if it is a {@link Catalog} to be registered with the
* {@link CatalogFactory} instance for our application. If the attribute
* specified to our constructor has a value, that will be used as the name
* under which to register this {@link Catalog}. Otherwise, this will
* become the default {@link Catalog} for this application.</p>
*
* @author Craig R. McClanahan
* @version $Revision: 155403 $ $Date: 2005-02-26 12:52:46 +0000 (Sat, 26 Feb 2005) $
*/
class ConfigCatalogRule extends Rule {
// ----------------------------------------------------------- Constructors
/**
* <p>Construct a new instance of this rule that looks for an attribute
* with the specified name.</p>
*
* @param nameAttribute Name of the attribute containing the name under
* which this command should be registered
* @param catalogClass Name of the implementation class for newly
* created {@link Catalog} instances
*/
public ConfigCatalogRule(String nameAttribute, String catalogClass) {
super();
this.nameAttribute = nameAttribute;
this.catalogClass = catalogClass;
}
// ----------------------------------------------------- Instance Variables
/**
* <p>The fully qualified class name of a {@link Catalog} class to use for
* instantiating new instances.</p>
*/
private String catalogClass = null;
/**
* <p>The name of the attribute under which we can retrieve the name
* this catalog should be registered with (if any).</p>
*/
private String nameAttribute = null;
// --------------------------------------------------------- Public Methods
/**
* <p>Retrieve or create a {@link Catalog} with the name specified by
* the <code>nameAttribute</code> attribute, or the default {@link Catalog}
* if there is no such attribute defined. Push it onto the top of the
* stack.</p>
*
* @param namespace the namespace URI of the matching element, or an
* empty string if the parser is not namespace aware or the element has
* no namespace
* @param name the local name if the parser is namespace aware, or just
* the element name otherwise
* @param attributes The attribute list of this element
*/
public void begin(String namespace, String name, Attributes attributes)
throws Exception {
// Retrieve any current Catalog with the specified name
Catalog catalog = null;
CatalogFactory factory = CatalogFactory.getInstance();
String nameValue = attributes.getValue(nameAttribute);
if (nameValue == null) {
catalog = factory.getCatalog();
} else {
catalog = factory.getCatalog(nameValue);
}
// Create and register a new Catalog instance if necessary
if (catalog == null) {
Class clazz = digester.getClassLoader().loadClass(catalogClass);
catalog = (Catalog) clazz.newInstance();
if (nameValue == null) {
factory.setCatalog(catalog);
} else {
factory.addCatalog(nameValue, catalog);
}
}
// Push this Catalog onto the top of the stack
digester.push(catalog);
}
}