/*
 * 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 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, Gunnar Rjnning, Peter Donald
/** * <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
Returns:the next Valve in the pipeline containing this Valve, if any.
/** * @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.
Params:
  • valve – The new next valve, or null if none
/** * 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.
/** * 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 getNext().invoke().
  • 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 getNext().invoke() method has returned.
  • Perform any actions on the output stream associated with the specified Response after the getNext().invoke() method has returned.
Params:
  • request – The servlet request to be processed
  • response – The servlet response to be created
Throws:
  • IOException – if an input/output error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
  • ServletException – if a servlet error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
/** * <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; public boolean isAsyncSupported(); }