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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.io.IOException;
import javax.servlet.ServletException;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
/**
* <p>A <b>Valve</b> 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 <code>invoke()</code> method below.</p>
*
* <b>HISTORICAL NOTE</b>: 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
*
*/
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 <code>null</code> 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();
/**
* <p>Perform request processing as required by this Valve.</p>
*
* <p>An individual Valve <b>MAY</b> perform the following actions, in
* the specified order:</p>
* <ul>
* <li>Examine and/or modify the properties of the specified Request and
* Response.
* <li>Examine the properties of the specified Request, completely generate
* the corresponding Response, and return control to the caller.
* <li>Examine the properties of the specified Request and Response, wrap
* either or both of these objects to supplement their functionality,
* and pass them on.
* <li>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 <code>getNext().invoke()</code>.
* <li>Examine, but not modify, the properties of the resulting Response
* (which was created by a subsequently invoked Valve or Container).
* </ul>
*
* <p>A Valve <b>MUST NOT</b> do any of the following things:</p>
* <ul>
* <li>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).
* <li>Create a completed Response <strong>AND</strong> pass this
* Request and Response on to the next Valve in the pipeline.
* <li>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.
* <li>Modify the HTTP headers included with the Response after the
* <code>getNext().invoke()</code> method has returned.
* <li>Perform any actions on the output stream associated with the
* specified Response after the <code>getNext().invoke()</code> method has
* returned.
* </ul>
*
* @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;
}
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