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 * Copyright 2004 The Apache Software Foundation
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// Portions Copyright [2018-2021] [Payara Foundation and/or its affiliates]
package org.apache.catalina;

import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;

import jakarta.servlet.ServletException;
import java.io.IOException;

/**
 * 
 * A Valve is a request processing component associated with a particular Container. A series of Valves are
 * generally associated with each other into a Pipeline. The detailed contract for a Valve is included in the
 * description of the invoke() method below.
 * 
 *
 * HISTORICAL NOTE: The "Valve" name was assigned to this concept because a valve is what you use in a real world
 * pipeline to control and/or modify flows through it.
 *
 * @author Craig R. McClanahan
 * @author Gunnar Rjnning
 * @author Peter Donald
 * @version $Revision: 303352 $ $Date: 2004-10-05 19:12:52 +0200 (mar., 05 oct. 2004) $
 */

public interface Valve {

    // -------------------------------------------------------------- Properties

    /**
     * Return descriptive information about this Valve implementation.
     */
    public String getInfo();

    /**
     * Return the next Valve in the pipeline containing this Valve, if any.
     */
    public Valve getNext();

    /**
     * Set the next Valve in the pipeline containing this Valve.
     *
     * @param valve The new next valve, or null if none
     */
    public void setNext(Valve valve);

    // ---------------------------------------------------------- Public Methods

    /**
     * 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();

    /**
     * 
     * Perform request processing as required by this Valve.
     * 
     *
     * 
     * An individual Valve MAY perform the following actions, in the specified order:
     * 
     * 
     * Examine and/or modify the properties of the specified Request and Response.
     * 
Examine the properties of the specified Request, completely generate the corresponding Response, and return
     * control to the caller.
     * 
Examine the properties of the specified Request and Response, wrap either or both of these objects to supplement
     * their functionality, and pass them on.
     * 
If the corresponding Response was not generated (and control was not returned, call the next Valve in the
     * pipeline (if there is one) by executing context.invokeNext().
     * 
Examine, but not modify, the properties of the resulting Response (which was created by a subsequently invoked
     * Valve or Container).
     * 
     *
     * 
     * A Valve MUST NOT do any of the following things:
     * 
     * 
     * Change request properties that have already been used to direct the flow of processing control for this request
     * (for instance, trying to change the virtual host to which a Request should be sent from a pipeline attached to a Host
     * or Context in the standard implementation).
     * 
Create a completed Response AND pass this Request and Response on to the next Valve in the
     * pipeline.
     * 
Consume bytes from the input stream associated with the Request, unless it is completely generating the response,
     * or wrapping the request before passing it on.
     * 
Modify the HTTP headers included with the Response after the invokeNext() method has returned.
     * 
Perform any actions on the output stream associated with the specified Response after the
     * invokeNext() method has returned.
     * 
     *
     * @param request The servlet request to be processed
     * @param response The servlet response to be created
     *
     * @exception IOException if an input/output error occurs, or is thrown by a subsequently invoked Valve, Filter, or
     * Servlet
     * @exception ServletException if a servlet error occurs, or is thrown by a subsequently invoked Valve, Filter, or
     * Servlet
     */
    public void invoke(Request request, Response response) throws IOException, ServletException;

    /**
     * Process a Comet event.
     *
     * @param request The servlet request to be processed
     * @param response The servlet response to be created
     *
     * @exception IOException if an input/output error occurs, or is thrown by a subsequently invoked Valve, Filter, or
     * Servlet
     * @exception ServletException if a servlet error occurs, or is thrown by a subsequently invoked Valve, Filter, or
     * Servlet
     */
    public void event(Request request, Response response, CometEvent event) throws IOException, ServletException;
}