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//
// ========================================================================
// Copyright (c) 1995 Mort Bay Consulting Pty Ltd and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
// which is available at https://www.apache.org/licenses/LICENSE-2.0.
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
// ========================================================================
//
package org.eclipse.jetty.ee9.webapp;
import java.util.Collection;
import java.util.Collections;
import java.util.ServiceLoader;
import org.eclipse.jetty.util.TopologicalSort;
/**
* A pluggable Configuration for {@link WebAppContext}s.
*
* A {@link WebAppContext} is configured by the application of one or more {@link Configuration}
* instances. Typically each implemented Configuration is responsible for an aspect of the
* servlet specification (eg {@link WebXmlConfiguration}, {@link FragmentConfiguration}, etc.)
* or feature (eg {@code JakartaWebSocketConfiguration}, {@code JmxConfiguration} etc.)
*
* Configuration instances are discovered by the {@link Configurations} class using either the
* {@link ServiceLoader} mechanism or by an explicit call to {@link Configurations#setKnown(String...)}.
* By default, all Configurations that do not return false from {@link #isEnabledByDefault()}
* are applied to all {@link WebAppContext}s within the JVM. However a Server wide default {@link Configurations}
* collection may also be defined with {@link Configurations#setServerDefault(org.eclipse.jetty.server.Server)}.
* Furthermore, each individual Context may have its Configurations list explicitly set and/or amended with
* {@link WebAppContext#setConfigurations(Configuration[])}, {@link WebAppContext#addConfiguration(Configuration...)}
* or {@link WebAppContext#getConfigurations()}.
*
* Since Jetty-9.4, Configurations are self ordering using the {@link #getDependencies()} and
* {@link #getDependents()} methods for a {@link TopologicalSort} initiated by {@link Configurations#sort()}
* when a {@link WebAppContext} is started. This means that feature configurations
* (eg {@link JndiConfiguration}, {@link JaasConfiguration}} etc.) can be added or removed without concern
* for ordering.
*
* Also since Jetty-9.4, Configurations are responsible for providing {@link #getServerClasses()} and
* {@link #getSystemClasses()} to configure the {@link WebAppClassLoader} for each context.
*
*/
public interface Configuration
{
String ATTR = "org.eclipse.jetty.ee9.webapp.configuration";
/**
* @return True if the feature this configuration represents is available and has all its dependencies.
*/
default boolean isAvailable()
{
return true;
}
/**
* Get a class that this class replaces/extends.
* If this is added to {@link Configurations} collection that already contains a
* configuration of the replaced class or that reports to replace the same class, then
* it is replaced with this instance.
*
* @return The class this Configuration replaces/extends or null if it replaces no other configuration
*/
default Class replaces()
{
return null;
}
/**
* Get known Configuration Dependencies.
*
* @return The names of Configurations that {@link TopologicalSort} must order
* before this configuration.
*/
default Collection getDependencies()
{
return Collections.emptyList();
}
/**
* Get known Configuration Dependents.
*
* @return The names of Configurations that {@link TopologicalSort} must order
* after this configuration.
*/
default Collection getDependents()
{
return Collections.emptyList();
}
/**
* Get the system classes associated with this Configuration.
*
* @return ClassMatcher of system classes.
*/
default ClassMatcher getSystemClasses()
{
return new ClassMatcher();
}
/**
* Get the server classes associated with this Configuration.
*
* @return ClassMatcher of server classes.
*/
default ClassMatcher getServerClasses()
{
return new ClassMatcher();
}
/**
* Set up for configuration.
*
* Typically this step discovers configuration resources.
* Calls to preConfigure may alter the Configurations configured on the
* WebAppContext, so long as configurations prior to this configuration
* are not altered.
*
* @param context The context to configure
* @throws Exception if unable to pre configure
*/
void preConfigure(WebAppContext context) throws Exception;
/**
* Configure WebApp.
*
* Typically this step applies the discovered configuration resources to
* either the {@link WebAppContext} or the associated {@link MetaData}.
*
* @param context The context to configure
* @throws Exception if unable to configure
*/
void configure(WebAppContext context) throws Exception;
/**
* Clear down after configuration.
*
* @param context The context to configure
* @throws Exception if unable to post configure
*/
void postConfigure(WebAppContext context) throws Exception;
/**
* DeConfigure WebApp.
* This method is called to undo all configuration done. This is
* called to allow the context to work correctly over a stop/start cycle
*
* @param context The context to configure
* @throws Exception if unable to deconfigure
*/
void deconfigure(WebAppContext context) throws Exception;
/**
* Destroy WebApp.
* This method is called to destroy a webappcontext. It is typically called when a context
* is removed from a server handler hierarchy by the deployer.
*
* @param context The context to configure
* @throws Exception if unable to destroy
*/
void destroy(WebAppContext context) throws Exception;
/**
* @return true if configuration is enabled by default
*/
boolean isEnabledByDefault();
/**
* @return true if configuration should be aborted
*/
boolean abort(WebAppContext context);
/**
* Experimental Wrapper mechanism for WebApp Configuration components.
*
* Beans in WebAppContext that implement this interface
* will be called to optionally wrap any newly created {@link Configuration}
* objects before they are used for the first time.
*
*/
interface WrapperFunction
{
Configuration wrapConfiguration(Configuration configuration);
}
class Wrapper implements Configuration
{
private Configuration delegate;
public Wrapper(Configuration delegate)
{
this.delegate = delegate;
}
public Configuration getWrapped()
{
return delegate;
}
@Override
public void preConfigure(WebAppContext context) throws Exception
{
delegate.preConfigure(context);
}
@Override
public void configure(WebAppContext context) throws Exception
{
delegate.configure(context);
}
@Override
public void postConfigure(WebAppContext context) throws Exception
{
delegate.postConfigure(context);
}
@Override
public void deconfigure(WebAppContext context) throws Exception
{
delegate.deconfigure(context);
}
@Override
public void destroy(WebAppContext context) throws Exception
{
delegate.destroy(context);
}
@Override
public boolean isEnabledByDefault()
{
return delegate.isEnabledByDefault();
}
@Override
public boolean abort(WebAppContext context)
{
return delegate.abort(context);
}
}
}