org.apache.catalina.Valve Maven / Gradle / Ivy
/*
* 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;
/**
* 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
*/
public interface Valve {
//-------------------------------------------------------------- Properties
/**
* Returns the next Valve in this pipeline, or null if this is
* the last Valve in the pipeline.
*
* @return the next Valve in the pipeline containing this Valve, or
* null 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 null 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();
/**
* 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.
*
*
* @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();
}