Valve (Apache Tomcat 8.0.15 API Documentation)

All Known Subinterfaces:

ClusterValve

All Known Implementing Classes:

AbstractAccessLogValve, AccessLogValve, AuthenticatorBase, BasicAuthenticator, ClusterSingleSignOn, CometConnectionManagerValve, CrawlerSessionManagerValve, DigestAuthenticator, ErrorReportValve, ExtendedAccessLogValve, FormAuthenticator, JDBCAccessLogValve, JvmRouteBinderValve, NonLoginAuthenticator, PersistentValve, RemoteAddrValve, RemoteHostValve, RemoteIpValve, ReplicationValve, RequestFilterValve, RewriteValve, SemaphoreValve, SingleSignOn, SpnegoAuthenticator, SSLAuthenticator, SSLValve, StuckThreadDetectionValve, ValveBase
```
public interface Valve
```
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

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`backgroundProcess()` Execute a periodic task, such as reloading, etc.
`void`	`event(Request request, Response response, CometEvent event)` Process a Comet event.
`Valve`	`getNext()` Return the next Valve in the pipeline containing this Valve, if any.
`void`	`invoke(Request request, Response response)` Perform request processing as required by this Valve.
`boolean`	`isAsyncSupported()`
`void`	`setNext(Valve valve)` Set the next Valve in the pipeline containing this Valve.

- Method Detail
  - getNext
```
Valve getNext()
```
    Return the next Valve in the pipeline containing this Valve, if any.
  - setNext
```
void setNext(Valve valve)
```
    Set the next Valve in the pipeline containing this Valve.
    
    Parameters:
    valve - The new next valve, or null if none
  - backgroundProcess
```
void backgroundProcess()
```
    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.
  - invoke
```
void invoke(Request request,
          Response response)
            throws IOException,
                   ServletException
```
    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.
    Parameters:
    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
  - event
```
void event(Request request,
         Response response,
         CometEvent event)
           throws IOException,
                  ServletException
```
    Process a Comet event.
    
    Parameters:
    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
  - isAsyncSupported
```
boolean isAsyncSupported()
```

Interface Valve

Method Summary

Method Detail

getNext

setNext

backgroundProcess

invoke

event

isAsyncSupported