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package org.apache.catalina;
import java.io.IOException;
import javax.servlet.ServletException;
/**
* <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
* @version $Revision: 1.3 $ $Date: 2007/05/05 05:31:52 $
*/
public interface Valve {
// START OF IASRI 4665318
// ----------------------------------------------------- Manifest Constants
/**
* A valve returns this value to indicate (to the pipeline) that the next
* valve in the pipeline can be invoked.
*/
public static final int INVOKE_NEXT = 1;
/**
* A valve returns this value to indicate that no further processing
* of the request should take place (along the rest of the pipeline).
* All valves that are function as 'basic' valves return this value
* as they are the 'last' valve in the pipeline. A valve (such as an
* authenticator) may return this value to stop a request from being
* processed further because the user/password could not be verified.
*/
public static final int END_PIPELINE = 2;
// END OF IASRI 4665318
//-------------------------------------------------------------- Properties
/**
* Return descriptive information about this Valve implementation.
*/
public String getInfo();
//---------------------------------------------------------- Public Methods
/**
* <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>context.invokeNext()</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>invokeNext()</code> method has returned.
* <li>Perform any actions on the output stream associated with the
* specified Response after the <code>invokeNext()</code> method has
* returned.
* </ul>
*
* @param request The servlet request to be processed
* @param response The servlet response to be created
* @param context The valve context used to invoke the next valve
* in the current processing pipeline
*
* @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
*/
/** START IASRI 4665318
public void invoke(Request request, Response response,
ValveContext context)
throws IOException, ServletException;
*/
// START OF IASRI 4665318
/**
* <li>In order to reduce the stack depth, a ValveContext is no longer
* passed into the <code>invoke()</code> method. Instead, the method
* returns either INVOKE_NEXT or END_PIPELINE to the caller
* (<code>Pipeline.invoke()</code>). This return code is used to
* determine whether the next valve in the pipeline should be
* invoked.
*
* @return <code>INVOKE_NEXT</code> or <code>END_PIPELINE</code>
*/
public int invoke(Request request, Response response)
throws IOException, ServletException;
/**
* <p>Perform post-request processing as required by this Valve.</p>
*
* @param request The servlet request to be processed
* @param response The servlet response to be created
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet error occurs
*/
public void postInvoke(Request request, Response response)
throws IOException, ServletException;
// END OF IASRI 4665318
}
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