SimpleXbQueue (xmlBlaster 1.6.2 client API)

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org.xmlBlaster.util
Class SimpleXbQueue

java.lang.Object
  org.xmlBlaster.util.SimpleXbQueue

public class SimpleXbQueue
extends java.lang.Object

This queue (FIFO) implementation may serve as your base class or as a member variable.
It is based on a linked list.

Example:

   int size = 3;
   Queue queue = new Queue("Test", size);
   queue.setModeToDiscardOldest(); // if queue is full, oldest entry is removed
   try {
       queue.push("Hello ");
       queue.push("world.");
   }
   catch (XmlBlasterException e) {
   }
   System.out.println(queue.pull()); // prints "Hello "
   System.out.println(queue.pull()); // prints "world."

TODO: Allow persistence store e.g. via JDBC bridge into Oracle with some smart caching

Version:: $Revision: 1.8 $
Author:: ruff@swand.lake.de

Constructor Summary
`SimpleXbQueue(java.lang.String name, int maxEntries)` Constructs an empty FIFO queue.

Method Summary
`long`	`getNumLost()` Counter for lost messages in 'discard' or 'discardOldest' mode
`boolean`	`isFull()` Check if the queue is filled up.
`static void`	`main(java.lang.String[] args)` This method is for testing only. To start this test type: `java org.xmlBlaster.util.SimpleXbQueue`
`java.lang.Object`	`pull()` Pull the next unit from the end of the queue.
`void`	`push(java.lang.Object obj)` Add a unit to the beginning of the queue.
`java.util.ListIterator`	`queueIterator(int index)` Returns a list-iterator of the elements in this list (in proper sequence), starting at the specified position in the list.
`void`	`setModeToDiscard()` Default is that an Exception is thrown if the queue is full.
`void`	`setModeToDiscardOldest()` Default is that an Exception is thrown if the queue is full.
`int`	`size()` How many objects are in the queue.

Methods inherited from class java.lang.Object

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

Constructor Detail

SimpleXbQueue

public SimpleXbQueue(java.lang.String name,
                     int maxEntries)

Constructs an empty FIFO queue.

Parameters:

name - A nice name, for error reporting only.

maxEntries - The maximum number of nodes for this queue.

Method Detail

isFull

public final boolean isFull()

Check if the queue is filled up.

Returns:: 'true' if space for at least on more entry does exist, 'false' if quota is exceeded.

pull

public final java.lang.Object pull()

Pull the next unit from the end of the queue.

Returns:: The last object of the queue or null if no element is in the queue.

push

public final void push(java.lang.Object obj)
                throws XmlBlasterException

Add a unit to the beginning of the queue.

Parameters:: obj - The object which should be added to the beginning of the queue.
Throws:: JUtilsException - This exception is thrown of no more space is available.; XmlBlasterException

queueIterator

public final java.util.ListIterator queueIterator(int index)
                                           throws java.lang.IndexOutOfBoundsException

Returns a list-iterator of the elements in this list (in proper sequence), starting at the specified position in the list.

TODO: Discuss thread safety when using this list.

Parameters:: index - Position of the first element to be returned from the list-iterator (by a call to next).
Returns:: A ListIterator of the elements in this list (in proper sequence), starting at the specified position in the list.
Throws:: java.lang.IndexOutOfBoundsException - if index is out of range (index < 0 || index > size()).

setModeToDiscardOldest

public void setModeToDiscardOldest()

Default is that an Exception is thrown if the queue is full. Calling this method changes the behavior that if the queue is filled, the supernumerary entries are falling out at the end and are lost.

setModeToDiscard

public void setModeToDiscard()