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  /*
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   * the License.  You may obtain a copy of the License at
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  * 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.
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 package org.apache.catalina;
 
 
 
 

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(s):
Craig R. McClanahan
Gunnar Rjnning
Peter Donald
Version:
$Revision: 1204 $ $Date: 2009-10-17 12:45:59 +0200 (Sat, 17 Oct 2009) $
 
 
 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.

Parameters:
valve The new next valve, or null 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();


    

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 context.invokeNext().
  • 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 invokeNext() method has returned.
  • Perform any actions on the output stream associated with the specified Response after the invokeNext() method has returned.

Parameters:
request The servlet request to be processed
response The servlet response to be created
Throws:
java.io.IOException if an input/output error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
javax.servlet.ServletException if a servlet error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
    public void invoke(Request requestResponse response)
        throws IOExceptionServletException;

    
    
Process an event.

Parameters:
request The servlet request to be processed
response The servlet response to be processed
event The event to be processed
Throws:
java.io.IOException if an input/output error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
javax.servlet.ServletException if a servlet error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
    public void event(Request requestResponse responseHttpEvent event)
        throws IOExceptionServletException;
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