org.eclipse.jetty.util

Class IteratingCallback

java.lang.Object

org.eclipse.jetty.util.IteratingCallback

All Implemented Interfaces:

Callback

public abstract class IteratingCallback
extends Object
implements Callback

Iterating Callback.

This specialised callback is used when breaking up an asynchronous task into smaller asynchronous tasks. A typical pattern is that a successful callback is used to schedule the next sub task, but if that task completes quickly and uses the calling thread to callback the success notification, this can result in a growing stack depth.

To avoid this issue, this callback uses an AtomicReference to note if the success callback has been called during the processing of a sub task, and if so then the processing iterates rather than recurses.

This callback is passed to the asynchronous handling of each sub task and a call the succeeded() on this call back represents completion of the subtask. Only once all the subtasks are completed is the Callback.succeeded() method called on the Callback instance passed the the IteratingCallback(Callback) constructor.

Nested Class Summary

Nested classes/interfaces inherited from interface org.eclipse.jetty.util.Callback

Callback.Adapter

Constructor Summary

Constructors

Constructor and Description
IteratingCallback(Callback callback)

Method Summary

Methods

Modifier and Type	Method and Description
void	failed(Throwable x) Callback invoked when the operation fails.
void	iterate() This method is called initially to start processing and is then called by subsequent sub task success to continue processing.
protected abstract boolean	process() Process a subtask.
void	succeeded() Callback invoked when the operation completes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

IteratingCallback

public IteratingCallback(Callback callback)

Method Detail

process

protected abstract boolean process()
                            throws Exception

Process a subtask.

Called by iterate() to process a sub task of the overall task

Returns:

True if the total task is complete. If false is returned then this Callback must be scheduled to receive either a call to succeeded() or failed(Throwable).

Throws:

Exception

iterate

public void iterate()

This method is called initially to start processing and is then called by subsequent sub task success to continue processing.

succeeded

public void succeeded()

Description copied from interface: Callback

Callback invoked when the operation completes.

Specified by:

succeeded in interface Callback

See Also:

Callback.failed(Throwable)

failed

public void failed(Throwable x)

Description copied from interface: Callback

Callback invoked when the operation fails.

Specified by:

failed in interface Callback

Parameters:

x - the reason for the operation failure