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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.catalina;
import java.beans.PropertyChangeListener;
/**
* A <b>Loader</b> represents a Java ClassLoader implementation that can be used by a Container to load class files
* (within a repository associated with the Loader) that are designed to be reloaded upon request, as well as a
* mechanism to detect whether changes have occurred in the underlying repository.
* <p>
* In order for a <code>Loader</code> implementation to successfully operate with a <code>Context</code> implementation
* that implements reloading, it must obey the following constraints:
* <ul>
* <li>Must implement <code>Lifecycle</code> so that the Context can indicate that a new class loader is required.
* <li>The <code>start()</code> method must unconditionally create a new <code>ClassLoader</code> implementation.
* <li>The <code>stop()</code> method must throw away its reference to the <code>ClassLoader</code> previously utilized,
* so that the class loader, all classes loaded by it, and all objects of those classes, can be garbage collected.
* <li>Must allow a call to <code>stop()</code> to be followed by a call to <code>start()</code> on the same
* <code>Loader</code> instance.
* <li>Based on a policy chosen by the implementation, must call the <code>Context.reload()</code> method on the owning
* <code>Context</code> when a change to one or more of the class files loaded by this class loader is detected.
* </ul>
*
* @author Craig R. McClanahan
*/
public interface Loader {
/**
* Execute a periodic task, such as reloading, etc. This method will be invoked inside the classloading context of
* this container. Unexpected throwables will be caught and logged.
*/
void backgroundProcess();
/**
* @return the Java class loader to be used by this Loader.
*/
ClassLoader getClassLoader();
/**
* @return the Context with which this Loader has been associated.
*/
Context getContext();
/**
* Set the Context with which this Loader has been associated.
*
* @param context The associated Context
*/
void setContext(Context context);
/**
* @return the "follow standard delegation model" flag used to configure our ClassLoader.
*/
boolean getDelegate();
/**
* Set the "follow standard delegation model" flag used to configure our ClassLoader.
*
* @param delegate The new flag
*/
void setDelegate(boolean delegate);
/**
* Add a property change listener to this component.
*
* @param listener The listener to add
*/
void addPropertyChangeListener(PropertyChangeListener listener);
/**
* Has the internal repository associated with this Loader been modified, such that the loaded classes should be
* reloaded?
*
* @return <code>true</code> when the repository has been modified, <code>false</code> otherwise
*/
boolean modified();
/**
* Remove a property change listener from this component.
*
* @param listener The listener to remove
*/
void removePropertyChangeListener(PropertyChangeListener listener);
}
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