/*
* 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 jakarta.servlet.ServletException;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
/**
* 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.
*/
public interface Valve {
// -------------------------------------------------------------- Properties
/**
* Returns the next Valve in this pipeline, or <code>null</code> if this is the last Valve in the pipeline.
*
* @return the next Valve in the pipeline containing this Valve, or <code>null</code> if this is the last Valve in
* the pipeline.
*/
Valve getNext();
/**
* Set the next Valve in the pipeline containing this Valve.
*
* @param valve The new next valve, or <code>null</code> if none
*/
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.
*/
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
*/
void invoke(Request request, Response response) throws IOException, ServletException;
boolean isAsyncSupported();
}