org.springframework.batch.repeat.support

Class ResultHolderResultQueue

java.lang.Object

org.springframework.batch.repeat.support.ResultHolderResultQueue

public class ResultHolderResultQueue
extends Object

An implementation of the ResultQueue that throttles the number of expected results, limiting it to a maximum at any given time.

Author:

Dave Syer

Constructor Summary

Constructors

Constructor and Description
ResultHolderResultQueue(int throttleLimit)

Method Summary

Methods

Modifier and Type	Method and Description
void	expect() Tell the queue to expect one more result.
boolean	isEmpty() Used by master thread to verify that there are results available from take() without possibly having to block and wait.
boolean	isExpecting() Check if any results are expected.
void	put(org.springframework.batch.repeat.support.ResultHolder holder) Once it is expecting a result, clients call this method to satisfy the expectation.
org.springframework.batch.repeat.support.ResultHolder	take() Get the next result as soon as it becomes available.

Methods inherited from class java.lang.Object

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

Constructor Detail

ResultHolderResultQueue

public ResultHolderResultQueue(int throttleLimit)

Parameters:

throttleLimit - the maximum number of results that can be expected at any given time.

Method Detail

isEmpty

public boolean isEmpty()

Used by master thread to verify that there are results available from take() without possibly having to block and wait.

Returns:

true if there are no results available

isExpecting

public boolean isExpecting()

Check if any results are expected. Usually used by master thread to drain queue when it is finished.

Returns:

true if more results are expected, but possibly not yet available.

expect

public void expect()
            throws InterruptedException

Tell the queue to expect one more result. Blocks until a new result is available if already expecting too many (as determined by the throttle limit).

Throws:

InterruptedException - if the call blocks and is then interrupted.

See Also:

ResultQueue.expect()

put

public void put(org.springframework.batch.repeat.support.ResultHolder holder)
         throws IllegalArgumentException

Once it is expecting a result, clients call this method to satisfy the expectation. In a master-worker pattern, the workers call this method to deposit the result of a finished task on the queue for collection.

Parameters:

holder - the result for later collection.

Throws:

IllegalArgumentException - if the queue is not expecting a new result

take

public org.springframework.batch.repeat.support.ResultHolder take()
                                                           throws NoSuchElementException,
                                                                  InterruptedException

Get the next result as soon as it becomes available.

Release result immediately if:

• There is a result that is continuable.

Otherwise block if either:

• There is no result (as per contract of ResultQueue).
• The number of results is less than the number expected.

Error if either:

• Not expecting.
• Interrupted.

Returns:

a result previously deposited

Throws:

NoSuchElementException - if there is no result expected

InterruptedException - if the operation is interrupted while waiting

See Also:

ResultQueue.take()