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org.apache.catalina.valves
Class SemaphoreValve

java.lang.Object
  extended by org.apache.catalina.valves.ValveBase
      extended by org.apache.catalina.valves.SemaphoreValve
All Implemented Interfaces:
javax.management.MBeanRegistration, Contained, Lifecycle, Valve
public class SemaphoreValve
extends ValveBase
implements Lifecycle

Implementation of a Valve that limits concurrency.

This Valve may be attached to any Container, depending on the granularity of the concurrency control you wish to perform.

Author:
Remy Maucherat

Field Summary
protected  boolean block
          Block until a permit is available.
protected  int concurrency
          Concurrency level of the semaphore.
protected  boolean fairness
          Fairness of the semaphore.
protected  boolean interruptible
          Block interruptibly until a permit is available.
protected  LifecycleSupport lifecycle
          The lifecycle event support for this component.
protected  java.util.concurrent.Semaphore semaphore
          Semaphore.
 
Fields inherited from class org.apache.catalina.valves.ValveBase
container, containerLog, controller, domain, mserver, next, oname
 
Fields inherited from interface org.apache.catalina.Lifecycle
AFTER_START_EVENT, AFTER_STOP_EVENT, BEFORE_START_EVENT, BEFORE_STOP_EVENT, DESTROY_EVENT, INIT_EVENT, PERIODIC_EVENT, START_EVENT, STOP_EVENT
 
Constructor Summary
SemaphoreValve()
           
 
Method Summary
 void addLifecycleListener(LifecycleListener listener)
          Add a lifecycle event listener to this component.
 boolean controlConcurrency(Request request, Response response)
          Subclass friendly method to add conditions.
 LifecycleListener[] findLifecycleListeners()
          Get the lifecycle listeners associated with this lifecycle.
 boolean getBlock()
           
 int getConcurrency()
           
 boolean getFairness()
           
 java.lang.String getInfo()
          Return descriptive information about this Valve implementation.
 boolean getInterruptible()
           
 void invoke(Request request, Response response)
          Do concurrency control on the request using the semaphore.
 void permitDenied(Request request, Response response)
          Subclass friendly method to add error handling when a permit isn't granted.
 void removeLifecycleListener(LifecycleListener listener)
          Remove a lifecycle event listener from this component.
 void setBlock(boolean block)
           
 void setConcurrency(int concurrency)
           
 void setFairness(boolean fairness)
           
 void setInterruptible(boolean interruptible)
           
 void start()
          Prepare for the beginning of active use of the public methods of this component.
 void stop()
          Gracefully terminate the active use of the public methods of this component.
 
Methods inherited from class org.apache.catalina.valves.ValveBase
backgroundProcess, createObjectName, event, getContainer, getContainerName, getController, getDomain, getNext, getObjectName, getParentName, postDeregister, postRegister, preDeregister, preRegister, setContainer, setController, setNext, setObjectName, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

semaphore

protected java.util.concurrent.Semaphore semaphore
Semaphore.

lifecycle

protected LifecycleSupport lifecycle
The lifecycle event support for this component.

concurrency

protected int concurrency
Concurrency level of the semaphore.

fairness

protected boolean fairness
Fairness of the semaphore.

block

protected boolean block
Block until a permit is available.

interruptible

protected boolean interruptible
Block interruptibly until a permit is available.

Constructor Detail

SemaphoreValve

public SemaphoreValve()
Method Detail

getConcurrency

public int getConcurrency()

setConcurrency

public void setConcurrency(int concurrency)

getFairness

public boolean getFairness()

setFairness

public void setFairness(boolean fairness)

getBlock

public boolean getBlock()

setBlock

public void setBlock(boolean block)

getInterruptible

public boolean getInterruptible()

setInterruptible

public void setInterruptible(boolean interruptible)

addLifecycleListener

public void addLifecycleListener(LifecycleListener listener)
Add a lifecycle event listener to this component.

Specified by:
addLifecycleListener in interface Lifecycle
Parameters:
listener - The listener to add

findLifecycleListeners

public LifecycleListener[] findLifecycleListeners()
Get the lifecycle listeners associated with this lifecycle. If this Lifecycle has no listeners registered, a zero-length array is returned.

Specified by:
findLifecycleListeners in interface Lifecycle

removeLifecycleListener

public void removeLifecycleListener(LifecycleListener listener)
Remove a lifecycle event listener from this component.

Specified by:
removeLifecycleListener in interface Lifecycle
Parameters:
listener - The listener to add

start

public void start()
           throws LifecycleException
Prepare for the beginning of active use of the public methods of this component. This method should be called after configure(), and before any of the public methods of the component are utilized.

Specified by:
start in interface Lifecycle
Throws:
LifecycleException - if this component detects a fatal error that prevents this component from being used

stop

public void stop()
          throws LifecycleException
Gracefully terminate the active use of the public methods of this component. This method should be the last one called on a given instance of this component.

Specified by:
stop in interface Lifecycle
Throws:
LifecycleException - if this component detects a fatal error that needs to be reported

getInfo

public java.lang.String getInfo()
Return descriptive information about this Valve implementation.

Specified by:
getInfo in interface Valve
Overrides:
getInfo in class ValveBase

invoke

public void invoke(Request request,
                   Response response)
            throws java.io.IOException,
                   javax.servlet.ServletException
Do concurrency control on the request using the semaphore.

Specified by:
invoke in interface Valve
Specified by:
invoke in class ValveBase
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
javax.servlet.ServletException - if a servlet error occurs

controlConcurrency

public boolean controlConcurrency(Request request,
                                  Response response)
Subclass friendly method to add conditions.

permitDenied

public void permitDenied(Request request,
                         Response response)
                  throws java.io.IOException,
                         javax.servlet.ServletException
Subclass friendly method to add error handling when a permit isn't granted.

Throws:
java.io.IOException
javax.servlet.ServletException
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