136 lines
8.7 KiB
HTML
136 lines
8.7 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 Platform Debugger Architecture" />
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<meta name="abstract" content="The Java Platform Debugger Architecture (JPDA) consists of the JVM Debug Interface/JVM Tool Interface, the Java Debug Wire Protocol, and the Java Debug Interface. All these parts of the JPDA enable any front end of a debugger that uses the JDWP to perform debugging operations. The debugger front end can either run remotely or run as an iSeries application." />
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<meta name="description" content="The Java Platform Debugger Architecture (JPDA) consists of the JVM Debug Interface/JVM Tool Interface, the Java Debug Wire Protocol, and the Java Debug Interface. All these parts of the JPDA enable any front end of a debugger that uses the JDWP to perform debugging operations. The debugger front end can either run remotely or run as an iSeries application." />
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<meta name="DC.Relation" scheme="URI" content="debug.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzahafsdebug.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="jpdebuga" />
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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 Platform Debugger Architecture</title>
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</head>
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<body id="jpdebuga"><a name="jpdebuga"><!-- --></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 Platform Debugger Architecture</h1>
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<div><p>The Java™ Platform Debugger Architecture (JPDA) consists
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of the JVM Debug Interface/JVM Tool Interface, the Java Debug Wire Protocol, and the Java Debug
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Interface. All these parts of the JPDA enable any front end of a debugger
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that uses the JDWP to perform debugging operations. The debugger front end
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can either run remotely or run as an iSeries™ application.</p>
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<div class="section"><img src="./delta.gif" alt="Start of change" /><h4 class="sectiontitle">Java Virtual Machine Tool Interface (JVMTI)</h4><p>JVMTI
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is the superceder of JVMDI and the Java Virtual Machine Profiler Interface
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(JVMPI). JVMTI contains all the functionality of both JVMDI and JVMPI, plus
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new functions. JVMTI was added as part of J2SE 5.0. In future releases, the
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JVMDI and JVMPI interfaces will no longer be offered, and JVMTI will be the
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only option available.</p>
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<p>A service program, called QJVAJVMTI, which resides
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in the QSYS library, supports the JVMTI functions.</p>
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<p>For more information
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about implementing JVMTI, see the <a href="http://java.sun.com/j2se/1.5.0/docs/guide/jvmti/index.html" target="_blank">JVMTI Reference page</a> at the Sun Microsystems, Inc.
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Web site.</p>
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<img src="./deltaend.gif" alt="End of change" /></div>
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<div class="section"><h4 class="sectiontitle">Java Virtual Machine Debug Interface</h4><p>In Java 2
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SDK (J2SDK), Standard Edition, version 1.2 or higher, the Java Virtual
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Machine Debug Interface (JVMDI) is part of Sun Microsystems, Inc. platform
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application program interfaces (APIs). JVMDI allows anyone to write a Java debugger
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for an iSeries server
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in iSeries C
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code. The debugger does not need to know the internal structure of the Java virtual
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machine since it uses JVMDI interfaces. JVMDI is the lowest-level interface
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in JPDA that is closest to the Java virtual machine.</p>
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<p>The debugger
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runs in the same multi-thread capable job as the Java virtual machine. The debugger uses Java Native
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Interface (JNI) Invocation APIs to create a Java virtual machine. It then places a hook
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at the beginning of a user class main method and calls the main method. When
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the main method begins, the hook is hit and debugging begins. Typical debug
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facilities are available, such as setting breakpoints, stepping, displaying
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variables, and changing variables.</p>
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<p>The debugger handles communication
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between the job where the Java virtual machine is running and a job
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handling the user interface. This user interface is either on your iSeries server
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or another system.</p>
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<p>A service program, called QJVAJVMDI that resides
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in the QSYS library, supports the JVMDI functions.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Java Debug Wire Protocol</h4><p>The Java Debug
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Wire Protocol (JDWP) is a defined communication protocol between a debugger
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process and the JVMDI/JVMTI. JDWP can be used from either a remote system
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or over a local socket. It is one layer removed from the JVMDI/JVMTI, but
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is a more complex interface.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Start JDWP in QShell</h4><p><img src="./delta.gif" alt="Start of change" />To start JDWP and
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run the Java class SomeClass, enter the following command in
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QShell:<img src="./deltaend.gif" alt="End of change" /></p>
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<pre>java -interpret -agentlib:jdwp=transport=dt_socket,
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address=8000,server=y,suspend=n SomeClass</pre>
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<p>In this example, JDWP
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listens for connections from remote debuggers on TCP/IP port 8000, but you
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can use any port number you want; dt_socket is the name of the SRVPGM that
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handles the JDWP transport and does not change.</p>
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<p><img src="./delta.gif" alt="Start of change" />For additional
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options that you can use with -Xrunjdwp, see <a href="http://java.sun.com/j2se/1.5.0/docs/guide/jpda/conninv.html" target="_blank">Sun VM Invocation Options</a> by Sun Microsystems, Inc.
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These options are available for both JDK 1.4 and 1.5 on i5/OS.<img src="./deltaend.gif" alt="End of change" /></p>
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</div>
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<div class="section"><img src="./delta.gif" alt="Start of change" /><h4 class="sectiontitle">Start JDWP from a CL command line</h4><p>To
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start JDWP with the CL command, two new options have been added: AGTPGM and
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AGTOPTIONS.</p>
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<p>The value of AGTPGM is JDWP and the value of AGTOPTIONS
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can be defined to be the same string that you would have used on the QShell
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command line. </p>
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<div class="p">To start JDWP and run the Java class SomeClass, enter
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the following command: <pre>JAVA CLASS(SomeClass) INTERPRET(*YES) AGTPGM(JDWP)
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AGTOPTIONS('transport=dt_socket,address=8000,server=y,suspend=n') </pre>
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</div>
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<p>Using
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JVMDI/JVMTI is not recommended for Direct Execution code. You should run your
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application with the interpreter, or use the Just-In_Time (JIT) Compiler with
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full-speed debugging.</p>
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<img src="./deltaend.gif" alt="End of change" /></div>
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<div class="section"><h4 class="sectiontitle">Java Debug Interface</h4><p>Java Debug
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Interface (JDI) is a high-level Java language interface provided for tool
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development. JDI hides the complexity of JVMDI/JVMTI and JDWP behind some Java class
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definitions. JDI is included in the rt.jar file, so the front end of the debugger
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exists on any platform that has Java installed.</p>
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<p>If you want to write
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debuggers for Java, you should use JDI because it is the simplest
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interface and your code is platform-independent.</p>
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<p>For more information
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on JDPA, see <a href="http://java.sun.com/j2se/1.3/docs/guide/jpda/architecture.html" target="_blank">Java Platform Debugger Architecture Overview</a> by
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Sun Microsystems, Inc.</p>
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</div>
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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="rzahafsdebug.htm">Full-Speed Debug</a></strong><br />
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The iSeries Java Virtual
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Machine (JVM) now supports "full-speed debugging". Prior to V5R3, enabling
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debugging meant disabling the Just-In-Time (JIT) compiler. Application performance
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suffered because many methods had to be run with the slow interpreter. This
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significant performance degradation was especially difficult for applications
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that could run for days before getting to the point where you wished to begin
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debugging.</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="debug.htm" title="To debug Java programs from the i5/OS command line, select one of the options listed here.">Debug Java programs from an i5/OS command line</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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