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package org.apache.catalina;
import java.io.IOException;
import javax.servlet.ServletException;
/**
* <p>Interface describing a collection of Valves that should be executed
* in sequence when the <code>invoke()</code> method is invoked. It is
* required that a Valve somewhere in the pipeline (usually the last one)
* must process the request and create the corresponding response, rather
* than trying to pass the request on.</p>
*
* <p>There is generally a single Pipeline instance associated with each
* Container. The container's normal request processing functionality is
* generally encapsulated in a container-specific Valve, which should always
* be executed at the end of a pipeline. To facilitate this, the
* <code>setBasic()</code> method is provided to set the Valve instance that
* will always be executed last. Other Valves will be executed in the order
* that they were added, before the basic Valve is executed.</p>
*
* @author Craig R. McClanahan
* @author Peter Donald
* @version $Revision: 1.3 $ $Date: 2007/05/05 05:31:51 $
*/
public interface Pipeline {
// ------------------------------------------------------------- Properties
/**
* <p>Return the Valve instance that has been distinguished as the basic
* Valve for this Pipeline (if any).
*/
public Valve getBasic();
/**
* <p>Set the Valve instance that has been distinguished as the basic
* Valve for this Pipeline (if any). Prioer to setting the basic Valve,
* the Valve's <code>setContainer()</code> will be called, if it
* implements <code>Contained</code>, with the owning Container as an
* argument. The method may throw an <code>IllegalArgumentException</code>
* if this Valve chooses not to be associated with this Container, or
* <code>IllegalStateException</code> if it is already associated with
* a different Container.</p>
*
* @param valve Valve to be distinguished as the basic Valve
*/
public void setBasic(Valve valve);
// --------------------------------------------------------- Public Methods
/**
* <p>Add a new Valve to the end of the pipeline associated with this
* Container. Prior to adding the Valve, the Valve's
* <code>setContainer()</code> method will be called, if it implements
* <code>Contained</code>, with the owning Container as an argument.
* The method may throw an
* <code>IllegalArgumentException</code> if this Valve chooses not to
* be associated with this Container, or <code>IllegalStateException</code>
* if it is already associated with a different Container.</p>
*
* @param valve Valve to be added
*
* @exception IllegalArgumentException if this Container refused to
* accept the specified Valve
* @exception IllegalArgumentException if the specifie Valve refuses to be
* associated with this Container
* @exception IllegalStateException if the specified Valve is already
* associated with a different Container
*/
public void addValve(Valve valve);
/**
* Return the set of Valves in the pipeline associated with this
* Container, including the basic Valve (if any). If there are no
* such Valves, a zero-length array is returned.
*/
public Valve[] getValves();
/**
* Cause the specified request and response to be processed by the Valves
* associated with this pipeline, until one of these valves causes the
* response to be created and returned. The implementation must ensure
* that multiple simultaneous requests (on different threads) can be
* processed through the same Pipeline without interfering with each
* other's control flow.
*
* @param request The servlet request we are processing
* @param response The servlet response we are creating
*
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet exception is thrown
*/
public void invoke(Request request, Response response)
throws IOException, ServletException;
/**
* Remove the specified Valve from the pipeline associated with this
* Container, if it is found; otherwise, do nothing. If the Valve is
* found and removed, the Valve's <code>setContainer(null)</code> method
* will be called if it implements <code>Contained</code>.
*
* @param valve Valve to be removed
*/
public void removeValve(Valve valve);
}
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