99 lines
6.7 KiB
HTML
99 lines
6.7 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 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="concept" />
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<meta name="DC.Title" content="Java Invocation API" />
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<meta name="abstract" content="The Invocation API, which is part of the Java Native Interface (JNI), allows non-Java code to create a Java virtual machine, and load and use Java classes. This function lets a multithreaded program make use of Java classes that are running in a single Java virtual machine in multiple threads." />
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<meta name="description" content="The Invocation API, which is part of the Java Native Interface (JNI), allows non-Java code to create a Java virtual machine, and load and use Java classes. This function lets a multithreaded program make use of Java classes that are running in a single Java virtual machine in multiple threads." />
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<meta name="DC.Relation" scheme="URI" content="jni.htm" />
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<meta name="DC.Relation" scheme="URI" content="invofunc.htm" />
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<meta name="DC.Relation" scheme="URI" content="multjvm.htm" />
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<meta name="DC.Relation" scheme="URI" content="invapiex.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="invocapi" />
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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>Java Invocation API</title>
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</head>
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<body id="invocapi"><a name="invocapi"><!-- --></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">Java Invocation API</h1>
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<div><p>The Invocation API, which is part of the Java™ Native
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Interface (JNI), allows non-Java code to create a Java virtual machine, and load and use Java classes.
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This function lets a multithreaded program make use of Java classes
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that are running in a single Java virtual machine in multiple threads.</p>
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<p></p>
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<p>The IBM<sup>®</sup> Developer
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Kit for Java supports the Java Invocation API for the following types
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of callers:</p>
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<ul><li>An ILE program or service program created for <samp class="codeph">STGMDL(*SNGLVL)</samp> and <samp class="codeph">DTAMDL(*P128)</samp></li>
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<li>An ILE program or service program created for <samp class="codeph">STGMDL(*TERASPACE)</samp> and <samp class="codeph">DTAMDL(*LLP64)</samp></li>
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<li>An <span class="keyword">i5/OS™</span> PASE executable
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created for either 32-bit or 64-bit AIX<sup>®</sup></li>
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</ul>
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<p>The application controls the Java virtual machine. The application can
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create the Java virtual machine, call Java methods (similar to the way in which
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an application calls subroutines), and destroy the Java virtual machine. Once you create the Java virtual
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machine, it remains ready to run within the process until the application
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explicitly destroys it. While being destroyed, the Java virtual machine performs clean-up,
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such as running finalizers, ending Java virtual machine threads, and releasing Java virtual
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machine resources.</p>
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<p>With a Java virtual machine that is ready to run, an application
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written in ILE languages, such as C and RPG, can call into the Java virtual
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machine to perform any function. It also can return from the Java virtual
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machine to the C application, call into the Java virtual machine again, and so on. The Java virtual
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machine is created once and does not have to be re-created before calling
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into the Java virtual machine to run a little or a lot of Java code.</p>
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<p>When using the Invocation API to run Java programs, the destination for STDOUT
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and STDERR is controlled by the use of an environment variable called QIBM_USE_DESCRIPTOR_STDIO.
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If this environment variable is set to Y or I (for example, QIBM_USE_DESCRIPTOR_STDIO=Y),
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the Java virtual
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machine uses file descriptors for STDIN (fd 0), STDOUT (fd 1), and STDERR
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(fd 2). In this case, the program must set these file descriptors to valid
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values by opening them as the first three files or pipes in this job. The
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first file opened in the job is given fd of 0, the second fd of 1, and third
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is fd of 2. For jobs initiated with the spawn API, these descriptors can be
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preassigned using a file descriptor map (see documentation on Spawn API).
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If the environment variable QIBM_USE_DESCRIPTOR_STDIO is not set or is set
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to any other value, file descriptors are not used for STDIN, STDOUT, or STDERR.
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Instead, STDOUT and STDERR are routed to a spooled file that is owned by the
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current job, and use of STDIN results in an IO exception.</p>
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<p>For an example that uses the Invocation API, see <a href="invapiex.htm">Example: Java Invocation
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API</a>. See <a href="invofunc.htm">Invocation API functions</a> for
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details about the Invocation API functions that are supported by the IBM Developer
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Kit for Java.</p>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="invofunc.htm">Invocation API functions</a></strong><br />
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The IBM Developer
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Kit for Java supports these Invocation API functions.</li>
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<li class="ulchildlink"><strong><a href="multjvm.htm">Support for multiple Java virtual machines</a></strong><br />
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Java on the iSeries™ server no longer supports creating
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more than one Java virtual machine (JVM) within a single job or process.
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This restriction affects only those users who create JVMs by using the Java Native
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Interface Invocation (JNI) API. This change in support does not affect how
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you use the java command to run your Java programs.</li>
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<li class="ulchildlink"><strong><a href="invapiex.htm">Example: Java Invocation API</a></strong><br />
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This example follows the standard Invocation API paradigm.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="jni.htm" title="You should only use native methods in cases where pure Java cannot meet your programming needs.">Use the Java Native Interface for native methods</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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