110 lines
6.4 KiB
HTML
110 lines
6.4 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Data queues" />
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<meta name="abstract" content="The DataQueue classes allow the Java program to interact with server data queues." />
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<meta name="description" content="The DataQueue classes allow the Java program to interact with server data queues." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="dtaq" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Data queues</title>
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</head>
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<body id="dtaq"><a name="dtaq"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Data queues</h1>
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<div><p>The DataQueue classes allow the Java™ program to interact with server data
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queues. </p>
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<div class="section"><p>Data queues on iSeries™ servers have the following characteristics:</p>
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<ul><li>The data queue allows for fast communications between jobs. Therefore,
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it is an excellent way to synchronize and pass data between jobs.</li>
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<li>Many jobs can simultaneously access the data queues.</li>
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<li>Messages on a data queue are free format. Fields are not required as they
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are in database files.</li>
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<li>The data queue can be used for either synchronous or asynchronous processing.</li>
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<li>The messages on a data queue can be ordered in one the following ways:
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<ul><li>Last-in first-out (LIFO). The last (newest) message that is placed on
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the data queue is the first message that is taken off the queue.</li>
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<li>First-in first-out (FIFO). The first (oldest) message that is placed on
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the data queue is the first message that is taken off the queue.</li>
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<li>Keyed. Each message on the data queue has a key associated with it. A
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message can be taken off the queue only by specifying the key that is associated
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with it.</li>
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</ul>
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</li>
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</ul>
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<p>The data queue classes provide a complete set of interfaces for accessing
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server data queues from your Java program. It is an excellent way to
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communicate between Java programs and programs on the server
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that are written in any programming language.</p>
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<p>A required parameter of
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each data queue object is the <a href="javadoc/com/ibm/as400/access/AS400.html#NAVBAR_TOP">AS400</a> object that represents the server that has the
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data queue or where the data queue is to be created.</p>
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<p>Using the data
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queue classes causes the AS400 object to connect to the server. See <a href="mngcon.htm#mngcon">managing connections</a> for information about
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managing connections.</p>
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<p>Each data queue object requires the integrated
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file system path name of the data queue. The type for the data queue is DTAQ.
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See <a href="ifspath.htm#ifspath"> integrated file system path names</a> for
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more information. </p>
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</div>
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<div class="section" id="dtaq__sequentialandkeyeddataqueues"><a name="dtaq__sequentialandkeyeddataqueues"><!-- --></a><h4 class="sectiontitle">Sequential and keyed data
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queues</h4><p>The data queue classes support the following data queues:</p>
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<ul><li><a href="dtaqseq.htm#dtaqseq">Sequential data queues</a></li>
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<li><a href="dtaqkey.htm#dtaqkey">Keyed data queues</a></li>
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</ul>
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<p>Methods common to both types of queues are in the <a href="javadoc/com/ibm/as400/access/BaseDataQueue.html#NAVBAR_TOP">BaseDataQueue</a> class.
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The <a href="javadoc/com/ibm/as400/access/DataQueue.html#NAVBAR_TOP"> DataQueue</a> class extends the BaseDataQueue class in order
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to complete the implementation of sequential data queues. The BaseDataQueue
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class is extended by the <a href="javadoc/com/ibm/as400/access/KeyedDataQueue.html#NAVBAR_TOP"> KeyedDataQueue</a> class to complete the implementation
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of keyed data queues.</p>
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<p>When data is read from a data queue, the data
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is placed in a <a href="javadoc/com/ibm/as400/access/DataQueueEntry.html#NAVBAR_TOP"> DataQueueEntry</a> object. This object holds the data for
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both keyed and sequential data queues. Additional data available when reading
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from a keyed data queue is placed in a <a href="javadoc/com/ibm/as400/access/KeyedDataQueueEntry.html#NAVBAR_TOP"> KeyedDataQueueEntry</a> object that extends the DataQueueEntry
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class.</p>
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<p>The data queue classes do not alter data that is written to or
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is read from the server data queue. The Java program must correctly format the data.
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The <a href="dtad.htm#dtad">data conversion classes</a> provide methods
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for converting data.</p>
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</div>
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<div class="section" id="dtaq__dqex1"><a name="dtaq__dqex1"><!-- --></a><h4 class="sectiontitle">Example: Using DataQueue and DataQueueEntry</h4><div class="p">The
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following example creates a DataQueue object, reads data from the DataQueueEntry
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object, and then disconnects from the system. <div class="note"><span class="notetitle">Note:</span> Read the <a href="codedisclaimer.htm#codedisclaimer">Code
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example disclaimer</a> for important legal information.</div>
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</div>
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<pre> // Create an AS400 object
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AS400 sys = new AS400("mySystem.myCompany.com");
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// Create the DataQueue object
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DataQueue dq = new DataQueue(sys, "/QSYS.LIB/MYLIB.LIB/MYQUEUE.DTAQ");
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// read data from the queue
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DataQueueEntry dqData = dq.read();
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// get the data out of the DataQueueEntry object.
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byte[] data = dqData.getData();
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// ... process the data
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// Disconnect since I am done using data queues
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sys.disconnectService(AS400.DATAQUEUE);</pre>
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</div>
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</div>
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</body>
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</html>
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