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package javax.servlet;

import java.util.Set;

/**
 * Interface which allows a library/runtime to be notified of a web
 * application's startup phase and perform any required programmatic
 * registration of servlets, filters, and listeners in response to it.
 *
 * Implementations of this interface may be annotated with
 * {@link javax.servlet.annotation.HandlesTypes HandlesTypes}, in order to
 * receive (at their {@link #onStartup} method) the Set of application
 * classes that implement, extend, or have been annotated with the class
 * types specified by the annotation.
 * 
 * 
If an implementation of this interface does not use this annotation,
 * or none of the application classes match the ones specified
 * by the annotation, the container must pass a null Set of classes
 * to {@link #onStartup}.
 *
 * 
When examining the classes of an application to
 * see if they match any of the criteria specified by the HandlesTypes
 * annotation of a ServletContainerInitializer, the container may run into
 * classloading problems if any of the application's optional JAR
 * files are missing. Because the container is not in a position to decide
 * whether these types of classloading failures will prevent
 * the application from working correctly, it must ignore them,
 * while at the same time providing a configuration option that would
 * log them. 
 *
 * 
Implementations of this interface must be declared by a JAR file
 * resource located inside the META-INF/services directory and
 * named for the fully qualified class name of this interface, and will be 
 * discovered using the runtime's service provider lookup mechanism
 * or a container specific mechanism that is semantically equivalent to
 * it. In either case, ServletContainerInitializer services from web
 * fragment JAR files excluded from an absolute ordering must be ignored,
 * and the order in which these services are discovered must follow the
 * application's classloading delegation model.
 *
 * @see javax.servlet.annotation.HandlesTypes
 *
 * @since Servlet 3.0
 */
public interface ServletContainerInitializer {

    /**
     * Notifies this ServletContainerInitializer of the startup
     * of the application represented by the given ServletContext.
     *
     * If this ServletContainerInitializer is bundled in a JAR
     * file inside the WEB-INF/lib directory of an application,
     * its onStartup method will be invoked only once during the
     * startup of the bundling application. If this
     * ServletContainerInitializer is bundled inside a JAR file
     * outside of any WEB-INF/lib directory, but still
     * discoverable as described above, its onStartup method
     * will be invoked every time an application is started.
     *
     * @param c the Set of application classes that extend, implement, or
     * have been annotated with the class types specified by the 
     * {@link javax.servlet.annotation.HandlesTypes HandlesTypes} annotation,
     * or null if there are no matches, or this
     * ServletContainerInitializer has not been annotated with
     * HandlesTypes
     *
     * @param ctx the ServletContext of the web application that
     * is being started and in which the classes contained in c
     * were found
     *
     * @throws ServletException if an error has occurred
     */
    public void onStartup(Set> c, ServletContext ctx)
        throws ServletException; 
}