// Copyright 2006, 2007 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.tapestry.internal.services;
import org.apache.tapestry.internal.event.InvalidationEventHub;
import org.apache.tapestry.ioc.services.ClassFactory;
/**
* Creates {@link org.apache.tapestry.internal.services.Instantiator}s for components, based on
* component class name. This will involve transforming the component's class before it is loaded.
* <p>
* In addition, a source acts as an event hub for
* {@link org.apache.tapestry.internal.events.InvalidationListener}s, so that any information derived from
* loaded classes can be discarded and rebuilt when classes change.
* <p>
* The strategy used is that when <em>any</em> class (in a controlled package) changes, the entire
* class loader is discarded, along with any instances derived from those classes. A new class
* loader is created, and then invalidation events are fired to listeners.
*/
public interface ComponentInstantiatorSource extends InvalidationEventHub
{
/**
* Given the name of a component class, provides an instantiator for that component.
* Instantiators are cached, so repeated calls to this method with the same class name will
* return the same instance; however, callers should also be aware that the instantiators may
* lose validity after an invalidation (caused by changes to external Java class files).
*
* @param classname
* FQCN to find (and perhaps transform and load)
* @return an object which can instantiate an instance of the component
*/
Instantiator findInstantiator(String classname);
/**
* Adds a controlled package. Only classes within controlled packages are subject to
* transformation.
*
* @param packageName
* the package name to add (must not be blank)
*/
void addPackage(String packageName);
/**
* Checks to see if a fully qualfied class name exists.
*
* @param className
* name of class to check
* @return true if the class exists (there's a ".class" file), false otherwise
*/
boolean exists(String className);
/**
* Returns a class factory that can be used to generate additional classes around enhanced
* classes, or create subclasses of enhanced classes.
*/
ClassFactory getClassFactory();
}
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