164 lines
9.7 KiB
HTML
164 lines
9.7 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 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="concept" />
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<meta name="DC.Title" content="Managing native method libraries" />
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<meta name="abstract" content="To use native method libraries, especially when you want to manage multiple versions of a native method library on your iSeries server, you need to understand both the Java library naming conventions and the library search algorithm." />
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<meta name="description" content="To use native method libraries, especially when you want to manage multiple versions of a native method library on your iSeries server, you need to understand both the Java library naming conventions and the library search algorithm." />
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<meta name="DC.Relation" scheme="URI" content="rzahapaseexmplsmain.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzahapasejavaenvvariables.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzahapaseerrors.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzahapaseexmpls.htm" />
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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="rzahapaseexmplslibrary" />
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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>Managing native method libraries</title>
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</head>
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<body id="rzahapaseexmplslibrary"><a name="rzahapaseexmplslibrary"><!-- --></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">Managing native method libraries</h1>
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<div><p>To use native method libraries, especially when you want to manage
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multiple versions of a native method library on your iSeries™ server, you need to understand
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both the Java™ library naming conventions and the library search
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algorithm.</p>
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<p><span class="keyword">i5/OS™</span> uses the first
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native method library that matches the name of the library that the Java virtual
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machine (JVM) loads. In order to ensure that <span class="keyword">i5/OS</span> finds
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the correct native methods, you must avoid library name clashes and confusion
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about which native method library the JVM uses.</p>
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<div class="section"><h4 class="sectiontitle"><span class="keyword">i5/OS</span> PASE
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and AIX<sup>®</sup> Java Library
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Naming Conventions</h4><p>If the Java code loads a library named Sample,
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the corresponding executable file must be named either libSample.a or libSample.so.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Java library search order</h4><p>When you enable <span class="keyword">i5/OS</span> PASE native methods for the
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JVM, your server uses three different lists (in the following order) to create
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a single native method library search path:</p>
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<ol><li><span class="keyword">i5/OS</span> library list</li>
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<li>LIBPATH environment variable</li>
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<li>PASE_LIBPATH environment variable</li>
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</ol>
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<p>In order to perform the search, <span class="keyword">i5/OS</span> converts
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the library list to the integrated file system format. QSYS file system objects
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have equivalent names in the integrated file system, but some integrated file
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system objects do not have equivalent QSYS file system names. Because the
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library loader looks for objects in both the QSYS file system and in the integrated
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file system, <span class="keyword">i5/OS</span> uses
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the integrated file system format to search for native method libraries.</p>
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<p>The
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following table shows how <span class="keyword">i5/OS</span> converts
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entries in the library list to the integrated file system format:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="border" border="1" rules="all"><thead align="left"><tr><th valign="top" id="d0e90">Library list entry</th>
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<th valign="top" id="d0e92">Integrated file system format</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e90 ">QSYS</td>
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<td valign="top" headers="d0e92 ">/qsys.lib</td>
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</tr>
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<tr><td valign="top" headers="d0e90 ">QSYS2</td>
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<td valign="top" headers="d0e92 ">/qsys.lib/qsys2.lib</td>
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</tr>
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<tr><td valign="top" headers="d0e90 ">QGPL</td>
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<td valign="top" headers="d0e92 ">/qsys.lib/qgpl.lib</td>
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</tr>
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<tr><td valign="top" headers="d0e90 ">QTEMP</td>
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<td valign="top" headers="d0e92 ">/qsys.lib/qtemp.lib</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p><strong>Example: Searching for the Sample2 library</strong></p>
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<p>In the
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following example, LIBPATH is set to /home/user1/lib32:/samples/lib32 and
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PASE_LIBPATH is set to /QOpenSys/samples/lib.</p>
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<p>The following table, when
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read from top to bottom, indicates the full search path:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="border" border="1" rules="all"><thead align="left"><tr><th valign="top" id="d0e128">Source</th>
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<th valign="top" id="d0e130">Integrated file system directories</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e128 ">Library list</td>
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<td valign="top" headers="d0e130 "><p>/qsys.lib<br />
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/qsys.lib/qsys2.lib<br />
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/qsys.lib/qgpl.lib<br />
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/qsys.lib/qtemp.lib</p>
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</td>
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</tr>
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<tr><td valign="top" headers="d0e128 ">LIBPATH</td>
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<td valign="top" headers="d0e130 "><p>/home/user1/lib32<br />
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/samples/lib32</p>
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</td>
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</tr>
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<tr><td valign="top" headers="d0e128 ">PASE_LIBPATH</td>
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<td valign="top" headers="d0e130 ">/QOpenSys/samples/lib</td>
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</tr>
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</tbody>
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</table>
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</div>
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<div class="note"><span class="notetitle">Note:</span> Uppercase and lowercase characters are significant only in the
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/QOpenSys path.</div>
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<p>In order to search for library Sample2, the Java library
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loader searches for file candidates in the following order:</p>
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<ol><li>/qsys.lib/sample2.srvpgm</li>
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<li>/qsys.lib/libSample2.a</li>
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<li>/qsys.lib/libSample2.so</li>
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<li>/qsys.lib/qsys2.lib/sample2.srvpgm</li>
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<li>/qsys.lib/qsys2.lib/libSample2.a</li>
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<li>/qsys.lib/qsys2.lib/libSample2.so</li>
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<li>/qsys.lib/qgpl.lib/sample2.srvpgm</li>
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<li>/qsys.lib/qgpl.lib/libSample2.a</li>
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<li>/qsys.lib/qgpl.lib/libSample2.so</li>
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<li>/qsys.lib/qtemp.lib/sample2.srvpgm</li>
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<li>/qsys.lib/qtemp.lib/libSample2.a</li>
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<li>/qsys.lib/qtemp.lib/libSample2.so</li>
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<li>/home/user1/lib32/sample2.srvpgm</li>
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<li>/home/user1/lib32/libSample2.a</li>
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<li>/home/user1/lib32/libSample2.so</li>
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<li>/samples/lib32/sample2.srvpgm</li>
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<li>/samples/lib32/libSample2.a</li>
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<li>/samples/lib32/libSample2.so</li>
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<li>/QOpenSys/samples/lib/SAMPLE2.srvpgm</li>
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<li>/QOpenSys/samples/lib/libSample2.a</li>
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<li>/QOpenSys/samples/lib/libSample2.so</li>
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</ol>
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<p><span class="keyword">i5/OS</span> loads the
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first candidate in the list that actually exists into the JVM as a native
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method library. Even though candidates like '/qsys.lib/libSample2.a' and '/qsys.lib/libSample2.so'
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occur in the search, it is not possible to create integrated file system files
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or symbolic links in the /qsys.lib directories. Therefore, even though <span class="keyword">i5/OS</span> checks for these candidate
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files, it will never find them in integrated file system directories that
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begin with /qsys.lib.</p>
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<p>However, you can create arbitrary symbolic links
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from other integrated file system directories to <span class="keyword">i5/OS</span> objects
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in the QSYS file system. As a result, valid file candidates include files
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such as /home/user1/lib32/sample2.srvpgm. </p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzahapaseexmplsmain.htm" title="The iSeries Java virtual machine (JVM) supports the use of native methods running in the i5/OS PASE environment. Prior to V5R2, the native iSeries JVM used only ILE native methods.">IBM i5/OS PASE native methods for Java</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rzahapasejavaenvvariables.htm" title="The Java virtual machine (JVM) uses the following variables to start i5/OS PASE environments. You need to set the QIBM_JAVA_PASE_STARTUP variable in order to run the IBM i5/OS PASE native method for Java example.">Java i5/OS PASE environment variables</a></div>
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<div><a href="rzahapaseerrors.htm" title="To help you troubleshoot i5/OS PASE native methods, this topic describes error conditions that are indicated by i5/OS job log messages and Java runtime exceptions. The following lists describe errors that you may encounter at start up or at run time when using i5/OS PASE native methods for Java.">Java i5/OS PASE error codes</a></div>
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<div><a href="rzahapaseexmpls.htm" title="The IBM i5/OS PASE native method for Java example calls an instance of a native C method that then uses Java Native Interface (JNI) to call back into Java code. Rather than accessing the string directly from Java code, the example calls a native method that then calls back into Java through JNI to get the string value.">Example: IBM i5/OS PASE native method for Java</a></div>
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</div>
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</div>
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</body>
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</html>
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