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package org.apache.catalina;

import java.beans.PropertyChangeListener;

A Loader 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.

In order for a Loader implementation to successfully operate with a Context implementation that implements reloading, it must obey the following constraints:

  • Must implement Lifecycle so that the Context can indicate that a new class loader is required.
  • The start() method must unconditionally create a new ClassLoader implementation.
  • The stop() method must throw away its reference to the ClassLoader previously utilized, so that the class loader, all classes loaded by it, and all objects of those classes, can be garbage collected.
  • Must allow a call to stop() to be followed by a call to start() on the same Loader instance.
  • Based on a policy chosen by the implementation, must call the Context.reload() method on the owning Context when a change to one or more of the class files loaded by this class loader is detected.
Author:Craig R. McClanahan
/** * 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.
/** * 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. */
public void backgroundProcess();
Returns:the Java class loader to be used by this Container.
/** * @return the Java class loader to be used by this Container. */
public ClassLoader getClassLoader();
Returns:the Context with which this Loader has been associated.
/** * @return the Context with which this Loader has been associated. */
public Context getContext();
Set the Context with which this Loader has been associated.
Params:
  • context – The associated Context
/** * Set the Context with which this Loader has been associated. * * @param context The associated Context */
public void setContext(Context context);
Returns:the "follow standard delegation model" flag used to configure our ClassLoader.
/** * @return the "follow standard delegation model" flag used to configure * our ClassLoader. */
public boolean getDelegate();
Set the "follow standard delegation model" flag used to configure our ClassLoader.
Params:
  • delegate – The new flag
/** * Set the "follow standard delegation model" flag used to configure * our ClassLoader. * * @param delegate The new flag */
public void setDelegate(boolean delegate);
Add a property change listener to this component.
Params:
  • listener – The listener to add
/** * Add a property change listener to this component. * * @param listener The listener to add */
public void addPropertyChangeListener(PropertyChangeListener listener);
Has the internal repository associated with this Loader been modified, such that the loaded classes should be reloaded?
Returns:true when the repository has been modified, false otherwise
/** * 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 */
public boolean modified();
Remove a property change listener from this component.
Params:
  • listener – The listener to remove
/** * Remove a property change listener from this component. * * @param listener The listener to remove */
public void removePropertyChangeListener(PropertyChangeListener listener); }