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Wed Oct 7 18:14:31 2009 UTC (4 years, 11 months ago) by nightmorph
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Updated Java guide for 64-bit plugins (bug 287675). Also removed some old cruft related to blackdown and old Sun versions.

1 <?xml version="1.0" encoding="UTF-8"?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/java.xml,v 1.43 2009/09/16 15:26:43 nightmorph Exp $ -->
3 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4
5 <guide link="/doc/en/java.xml">
6 <title>Gentoo Java Guide</title>
7
8 <author title="Author">
9 <mail link="nichoj@gentoo.org">Joshua Nichols</mail>
10 </author>
11 <author title="Author">
12 <mail link="karltk@gentoo.org">Karl Trygve Kalleberg</mail>
13 </author>
14 <author title="Editor">
15 <mail link="nightmorph@gentoo.org">Joshua Saddler</mail>
16 </author>
17
18 <abstract>
19 This guide will introduce you to Java and explain how to use Java with Gentoo
20 Linux.
21 </abstract>
22
23 <!-- The content of this document is licensed under the CC-BY-SA license -->
24 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
25 <license/>
26
27 <version>0.19</version>
28 <date>2009-10-07</date>
29
30 <chapter>
31 <title>What is Java?</title>
32 <section>
33 <title>Overview</title>
34 <body>
35
36 <p>
37 Java is a programming language developed by engineers of Sun Microsystems. The
38 language is object-oriented and designed to run on multiple platforms without
39 the need of recompiling code for each platform. Although Java can be compiled
40 as a native program, much of Java's popularity can be attributed to its
41 portability, along with other features such as garbage collection. To make
42 platform independence possible the Java compiler compiles the Java code to an
43 intermediate representation called "Java bytecode" that runs on a JRE (Java
44 Runtime Environment) and not directly on the operating system.
45 </p>
46
47 <p>
48 In order to run Java bytecode, one needs to have a JRE (Java Runtime
49 Environment) installed. A JRE provides core libraries, a platform dependent
50 Java Virtual Machine, plugins for browsers, among other things. A JDK (Java
51 Development Kit) adds programming tools, such as a bytecode compiler and a
52 debugger.
53 </p>
54
55 </body>
56 </section>
57 </chapter>
58
59 <chapter>
60 <title>Before You Begin</title>
61 <section>
62 <title>Existing installs</title>
63 <body>
64
65 <p>
66 For existing installs, regardless of if you have installed anything Java
67 before, make sure you have followed the <uri
68 link="/proj/en/java/java-upgrade.xml">Java Upgrade Guide</uri>.
69 </p>
70
71 </body>
72 </section>
73 <section>
74 <title>New installs</title>
75 <body>
76
77 <p>
78 New installs should require no further preparation.
79 </p>
80
81 </body>
82 </section>
83 </chapter>
84
85 <chapter>
86 <title>Installing a Virtual Machine</title>
87 <section>
88 <title>The choices</title>
89 <body>
90
91 <p>
92 Gentoo provides numerous Runtime Environments (JREs) and Development Kits
93 (JDKs). Among the current choices, we have:
94 </p>
95
96 <table>
97 <tr>
98 <th>Vendor</th>
99 <th>JDK</th>
100 <th>JRE</th>
101 </tr>
102 <tr>
103 <ti>The Blackdown Java Kit</ti>
104 <ti>dev-java/blackdown-jdk</ti>
105 <ti>dev-java/blackdown-jre</ti>
106 </tr>
107 <tr>
108 <ti>Sun's Java Kit</ti>
109 <ti>dev-java/sun-jdk</ti>
110 <ti>dev-java/sun-jre-bin</ti>
111 </tr>
112 <tr>
113 <ti>The IBM Java Kit</ti>
114 <ti>dev-java/ibm-jdk-bin</ti>
115 <ti>dev-java/ibm-jre-bin</ti>
116 </tr>
117 <tr>
118 <ti>BEA WebLogic's J2SE Development Kit</ti>
119 <ti>dev-java/jrockit-jdk-bin</ti>
120 </tr>
121 </table>
122
123 <!--
124 TODO: list free implementations?
125 note about not drop-in replacements
126 kaffe/sablevm/gcj/jamvm
127 -->
128 <p>
129 The default for Java 1.6 is the Sun JRE/JDK pair.
130 </p>
131
132 </body>
133 </section>
134 <section>
135 <title>Installing a JRE/JDKs</title>
136 <body>
137
138 <p>
139 To install your profile's default JDK, you can run <c>emerge virtual/jdk</c>.
140 Or to install your profile's default JRE, you can <c>emerge virtual/jre</c>.
141 </p>
142
143 <p>
144 In recent events, Sun has relicensed their JDK and JRE under a more Linux
145 distro friendly license. As a result, Sun releases Java 1.5 and onwards are
146 freely downloadable, without any further hassle.
147 </p>
148
149 <note>
150 A JDK also includes a JRE, so if you install a JDK you shouldn't have to also
151 have to install a JRE.
152 </note>
153
154 </body>
155 </section>
156 <section>
157 <title>Installing fetch-restricted virtual machines</title>
158 <body>
159
160 <p>
161 Some of the JDKs and JREs require you to jump through a few hoops before
162 installing. Simply emerge the packages as you normally would. The ebuilds will
163 then instruct you where to go and what to download.
164 </p>
165
166 <p>
167 You should download the indicated file(s) into
168 <path>/usr/portage/distfiles</path>. Once there, you can rerun the emerge
169 command, at which point the JRE/JDK will be begin to install.
170 </p>
171
172 </body>
173 </section>
174 </chapter>
175
176 <chapter>
177 <title>Configuring your virtual machine</title>
178 <section>
179 <title>Overview</title>
180 <body>
181
182 <p>
183 Gentoo has the ability to have multiple JDKs and JREs installed without causing
184 conflicts.
185 </p>
186
187 <p>
188 Using the <c>java-config</c> tool, you can set the system-wide default
189 (provided you have root access). Users can also use <c>java-config</c> to set
190 up their own personal default.
191 </p>
192
193 <note>
194 You can also use <e>eselect</e> to change the system and user vm. See
195 <c>eselect java-vm help</c>.
196 </note>
197
198 </body>
199 </section>
200 <section>
201 <title>Setting a default virtual machine</title>
202 <body>
203
204 <p>
205 Running the command <c>java-config --list-available-vms</c> will give you a
206 list of all JREs and JDKs installed on your system. Here is an example of
207 output:
208 </p>
209
210 <pre caption="Listing available VMs">
211 # <i>java-config --list-available-vms</i>
212 The following VMs are available for generation-2:
213 1) Blackdown JDK 1.4.2.03 [blackdown-jdk-1.4.2] <comment>(Build Only)</comment>
214 2) Blackdown JRE 1.4.2.03 [blackdown-jre-1.4.2] <comment>(Build Only)</comment>
215 3) IcedTea6-bin 1.4.1 [icedtea6-bin]
216 4) Sun JDK 1.5.0.20 [sun-jdk-1.5] <comment>(Build Only)</comment>
217 *) Sun JDK 1.6.0.16 [sun-jdk-1.6]
218 </pre>
219
220 <note>
221 VMs marked as Build Only may contain security vulnerabilities and/or be EOL.
222 Gentoo recommends not setting these VMs as either your system or user VM.
223 Please see <uri link="java.xml#build-only">Build Only VM</uri> for more
224 information.
225 </note>
226
227 <p>
228 The <e>*</e> indicates this is the current active vm (system-vm or user-vm when
229 set). The name in the brackets (<e>[]</e>) is the handle or ID for that
230 particular VM. You use the handle or the number to <c>java-config
231 --set-system-vm</c>. Here is an example of how to set the system VM.
232 </p>
233
234 <pre caption="Setting the System VM">
235 <comment>(By handle (preferred))</comment>
236 # <i>java-config --set-system-vm blackdown-jdk-1.4</i>
237 Now using blackdown-jdk-1.4 as your generation-2 system JVM
238 WARNING: blackdown-jdk-1.4 is marked as a build-only JVM. Using this vm is not recommended.
239 <comment>(By number)</comment>
240 # <i>java-config --set-system-vm 5</i>
241 Now using sun-jdk-1.6 as your generation-2 system JVM
242 </pre>
243
244 <p>
245 As a regular user, you can use <c>java-config --set-user-vm</c>.
246 </p>
247
248 <note>
249 You no longer have to <c>source</c> the profile for updates to the user/system
250 VM take place.
251 </note>
252
253 </body>
254 </section>
255 <section id="build-only">
256 <title>Build Only VM</title>
257 <body>
258
259 <p>
260 Some virtual machines are flagged as build-only due to being EOL and/or
261 containing security vulnerabilities. These virtual machines will not
262 automatically be used by Gentoo for the running of applications using Gentoo
263 launchers but will still be available for use by Gentoo's build environment as
264 some packages may require them for building. The setting of these virtual
265 machines as either your system or user VM is strongly discouraged as these VMs
266 will then be used when running the <path>/usr/bin/{java,javac,..}</path>
267 executables and will also be used by any packages not using Gentoo's launcher
268 scripts.
269 </p>
270
271 </body>
272 </section>
273 <section id="preferred-vm">
274 <title>Preferred VM</title>
275 <body>
276
277 <p>
278 While merging Java packages, the VM can and will be switched as necessary.
279 </p>
280
281 <p>
282 Because of the wide variety of available VMs, we do not have the resources to
283 test and verify every package works on all of them. So to ensure that every
284 packages merges smoothly, we have defined a list of <e>default/supported
285 VMs</e> per arch. You can find them in
286 <path>/usr/share/java-config-2/config/jdk-defaults.conf</path>. When you are
287 merging a Java package, and it detects one of the VM in that file is installed,
288 it will automatically use that VM, instead of the system-vm.
289 </p>
290
291 <p>
292 The merge time VM switching is also needed when, for example, your system-vm is
293 set a 1.4 VM and the package you are merging requires a 1.5 VM. While merging
294 it will use the preferred 1.5 VM, leaving your system-vm choice intact.
295 </p>
296
297 <p>
298 Of course, Gentoo is all about choice, so you can override these defaults in
299 <path>/etc/java-config-2/build/jdk.conf</path> and have complete control over
300 which VM will get used. Some examples:
301 </p>
302
303 <pre caption="Example /etc/java-config-2/build/jdk.conf">
304 <comment>(I always want it to use a sun-jdk, ie sun-jdk-1.4 for 1.4, sun-jdk-1.5 for 1.5, etc)</comment>
305 *=sun-jdk
306 </pre>
307
308 <pre caption="Example /etc/java-config-2/build/jdk.conf">
309 <comment>(Always use sun-jdk-1.5 wherever possible, except for when a 1.4 or 1.3 VM is explicitly required)</comment>
310 *=sun-jdk-1.5
311 </pre>
312
313 <pre caption="Example /etc/java-config-2/build/jdk.conf">
314 <comment># For 1.3 I prefer sun-jdk 1.4 but when it is not available, use ibm-jdk-bin,
315 # For 1.4, use blackdown-jdk, and for 1.5, use sun-jdk </comment>
316 1.3=sun-jdk-1.4 ibm-jdk-bin
317 1.4=blackdown-jdk
318 1.5=sun-jdk
319 </pre>
320
321 <warn>
322 You do not have to edit this file. If you change these options to use a
323 unsupported VM, things could possibly break. Bugs reported with a unsupported
324 VM won't be prioritized as much as bugs present within supported VMs.
325 </warn>
326
327 </body>
328 </section>
329 </chapter>
330
331 <chapter>
332 <title>Compilers</title>
333 <section>
334 <body>
335
336 <p>
337 The standard Java compiler used for building is javac, which comes with each
338 JDK. In addition to configuring the VM used at build time, it is also possible
339 configure which compiler is used. Essentially, you define a list your
340 preference for which compiler to use in
341 <path>/etc/java-config-2/build/compilers.conf</path>.
342 </p>
343
344 <pre caption="/etc/java-config-2/build/compilers.conf">
345 # If the ebuild supports it
346 # it will check the COMPILERS var front to back and
347 # use the first compiler that is installed
348
349 COMPILERS="ecj-3.1 jikes javac"
350 </pre>
351
352 <p>
353 Some compilers don't support all possible -target and -source arguments.
354 Therefore, each compiler in the list is checked to see if it can support the
355 desired -source/-target. javac will work in all cases, so if no other suitable
356 compiler is found, it will be used instead.
357 </p>
358
359 <p>
360 More details about each compiler are provided below:
361 </p>
362
363 <table>
364 <tr>
365 <th>Name</th>
366 <th>Handle</th>
367 <th>Package</th>
368 <th>Description</th>
369 </tr>
370 <tr>
371 <ti>javac</ti>
372 <ti>javac</ti>
373 <ti>N/A</ti>
374 <ti>
375 This is the default compiler that will be used, and comes with each JDK.
376 </ti>
377 </tr>
378 <tr>
379 <ti>jikes</ti>
380 <ti>jikes</ti>
381 <ti>dev-java/jikes</ti>
382 <ti>
383 Jikes was originally developed by IBM. Anecdotally, it is generally quicker
384 than javac. Note however, that it is more pedantic, and will fail under a
385 few circumstances where javac has no issue. It also does not support Java
386 1.5 syntax yet.
387 </ti>
388 </tr>
389 <tr>
390 <ti>Eclipse Compiler for Java</ti>
391 <ti>ecj-3.1</ti>
392 <ti>=dev-java/eclipse-ecj-3.1*</ti>
393 <ti>
394 ECJ is the compiler used by the Eclipse software development kit. It is
395 very full featured, and is pretty fast. It does support Java 1.5 syntax.
396 </ti>
397 </tr>
398 </table>
399
400 </body>
401 </section>
402 </chapter>
403
404 <chapter>
405 <title>Setting a default CLASSPATH</title>
406 <section>
407 <body>
408
409 <warn>
410 The options explained in this section should be considered deprecated and will
411 most likely be removed in the future. We strongly recommend against using
412 these, because your Java projects or application should ideally manage their
413 own classpaths. If you choose to specify a default CLASSPATH, some applications
414 may behave unexpectedly, because classes they weren't expecting would be on the
415 classpath.
416 </warn>
417
418 <p>
419 <c>java-config</c> can also be used to set a system-wide default CLASSPATH, as
420 well a user-specific default CLASSPATH.
421 </p>
422
423 <p>
424 First, you will want to list available Java libraries installed on your system
425 that might want to be put in your CLASSPATH. Here is an example of output:
426 </p>
427
428 <pre caption="Listing classes">
429 # <i>java-config --list-available-packages</i>
430 [xerces-2] The next generation of high performance, fully compliant XML parsers in the Apache Xerces family (/usr/share/xerces-2/package.env)
431 [junit] Simple framework to write repeatable tests (/usr/share/junit/package.env)
432 [bsh] BeanShell: A small embeddable Java source interpreter (/usr/share/bsh/package.env)
433 [bcel] The Byte Code Engineering Library: analyze, create, manipulate Java class files (/usr/share/bcel/package.env)
434 [log4j] A low-overhead robust logging package for Java (/usr/share/log4j/package.env)
435 ...
436 </pre>
437
438 <p>
439 Again, the names in brackets (<e>[]</e>) are the IDs that you have to pass to
440 <c>java-config --set-system-classpath</c>. Here is an example:
441 </p>
442
443 <pre caption="Setting classpaths">
444 # <i>java-config --set-system-classpath log4j,xerces-2</i>
445 </pre>
446
447 <note>
448 The current directory (<path>.</path>) will not be part of the system
449 classpath, as that should be added in your system's login profile.
450 </note>
451
452 <p>
453 You will have to update your environment by logging out, then in again or
454 sourcing <path>/etc/profile</path>.
455 </p>
456
457 <p>
458 For users, <c>java-config --set-user-classpath</c> will create
459 <path>~/.gentoo/java-env-classpath</path>, which you should then source from
460 your shell's profile.
461 </p>
462
463 <pre caption="Sourcing user specific classpath">
464 <i>if [[ -f "${HOME}/.gentoo/java-env-classpath" ]]; then
465 source ${HOME}/.gentoo/java-env-classpath
466 fi</i>
467 </pre>
468
469 <p>
470 If you really want a system wide or user default classpath you can add
471 something like the following to your shell's profile. But we would advise
472 against it.
473 </p>
474
475 <pre caption="Setting classpath">
476 # <i>export CLASSPATH="${CLASSPATH}:$(java-config --classpath log4j,xerces-2)"</i>
477 </pre>
478
479 </body>
480 </section>
481 </chapter>
482
483 <chapter>
484 <title>Java Browser Plugins</title>
485 <section>
486 <title>Installing a plugin</title>
487 <body>
488
489 <p>
490 You can install a Java plugin for your web browser by emerging a Java VM with
491 the <c>nsplugin</c> USE flag set.
492 </p>
493
494 <note>
495 <c>nsplugin</c> is not available for all architectures. Check for available
496 plugins on your arch before trying to install a VM by running <c>emerge -pv
497 &lt;java-vm&gt;</c>.
498 </note>
499
500 <p>
501 Portage will allow you to install multiple versions of Java plugins, though
502 only one will be used by your browser. You can check the list of available
503 plugins by running:
504 </p>
505
506 <pre caption="Viewing available plugins">
507 # <i>eselect java-nsplugin list</i>
508 [1] sun-jre-bin-1.6
509 [2] icedtea6-bin
510 </pre>
511
512 <p>
513 In this example, <c>sun-jre-bin</c> is selected for the browser plugin.
514 </p>
515
516 <pre caption="Selecting a plugin">
517 # <i>eselect java-nsplugin set sun-jre-bin-1.6</i>
518 </pre>
519
520 <p>
521 Verify that the correct plugin was selected:
522 </p>
523
524 <pre caption="Verifying the correct plugin">
525 # <i>eselect java-nsplugin list</i>
526 [1] sun-jre-bin-1.6 current
527 [2] icedtea6-bin
528 </pre>
529
530 <p>
531 Java.com also provides a link to <uri
532 link="http://java.com/en/download/installed.jsp">verify your installed
533 plugin</uri>. Additionally, if you are using a Mozilla-based browser, you can
534 verify your Java plugin by typing <c>about:plugins</c> into the address bar.
535 </p>
536
537 </body>
538 </section>
539 <section>
540 <title>Plugins on multilib systems</title>
541 <body>
542
543 <p>
544 If you are running a mixed 64-bit and 32-bit multilib system (for example, on
545 AMD64), you can use 64-bit and 32-bit Java plugins. Unless you have a pressing
546 need to run 32-bit Java applications, we recommend using native 64-bit plugins
547 on 64-bit web browsers.
548 </p>
549
550 <p>
551 There are several native 64-bit browser plugins available. The default JDK/JRE
552 pair, <c>sun-jdk</c> and <c>sun-jre-bin</c>, both include browser plugins. Just
553 emerge one of them with the <c>nsplugin</c> USE flag enabled.
554 </p>
555
556 <pre caption="Installing a 64-bit plugin">
557 # <i>echo "dev-java/sun-jre-bin nsplugin" >> /etc/portage/package.use</i>
558 # <i>emerge sun-jre-bin</i>
559 </pre>
560
561 <p>
562 To use a 32-bit plugin on a 32-bit browser, you will need to emerge
563 <c>emul-linux-x86-java</c> with the <c>nsplugin</c> USE flag enabled.
564 </p>
565
566 <pre caption="Installing a 32-bit plugin">
567 # <i>echo "app-emulation/emul-linux-x86-java nsplugin" >> /etc/portage/package.use</i>
568 # <i>emerge emul-linux-x86-java</i>
569 </pre>
570
571 <p>
572 Next, check which plugins are available:
573 </p>
574
575 <pre caption="Viewing available plugins">
576 # <i>eselect java-nsplugin list</i>
577 Available 32-bit Java browser plugins
578 [1] emul-linux-x86-java-1.5
579 [2] emul-linux-x86-java-1.6
580 Available 64-bit Java browser plugins
581 [1] icedtea6-bin
582 [2] sun-jre-bin-1.6
583 </pre>
584
585 <p>
586 Now select the right plugin for your browsers:
587 </p>
588
589 <pre caption="Selecting plugins">
590 <comment>(Choose the plugins for 32-bit and 64-bit browsers)</comment>
591 # <i>eselect java-nsplugin set 32bit emul-linux-x86-java-1.6</i>
592 # <i>eselect java-nsplugin set 64bit sun-jre-bin-1.6</i>
593 </pre>
594
595 <p>
596 Verify the correct plugin was selected:
597 </p>
598
599 <pre caption="Verifying the correct plugin">
600 # <i>eselect java-nsplugin list</i>
601 Available 32-bit Java browser plugins
602 [1] emul-linux-x86-java-1.5
603 [2] emul-linux-x86-java-1.6 current
604 Available 64-bit Java browser plugins
605 [1] icedtea6-bin
606 [2] sun-jre-bin-1.6 current
607 </pre>
608
609 </body>
610 </section>
611 </chapter>
612
613 <chapter>
614 <title>USE flags for use with Java</title>
615 <section>
616 <title>Setting USE flags</title>
617 <body>
618
619 <p>
620 For more information regarding USE flags, refer to the <uri
621 link="/doc/en/handbook/handbook-x86.xml?part=2&amp;chap=2">USE flags</uri>
622 chapter from the Gentoo Handbook.
623 </p>
624
625 </body>
626 </section>
627 <section>
628 <title>The flags</title>
629 <body>
630
631 <ul>
632 <li>The <b>java</b> flag adds support for Java in a variety of programs</li>
633 <li>
634 The <b>nsplugin</b> flag adds support for Mozilla-like browsers (including
635 Firefox). You will need this for viewing Java applets in your Mozilla-like
636 browser.
637 </li>
638 <li>
639 The <b>source</b> flag installs a zip of the source code of a package.
640 This is traditionally used for IDEs to 'attach' source to the libraries you
641 are using.
642 </li>
643 <li>The <b>jce</b> flag adds support for the Java Cryptography Engine</li>
644 <li>
645 For Java packages, the <b>doc</b> flag will build API documentation using
646 javadoc.
647 </li>
648 </ul>
649
650 </body>
651 </section>
652 </chapter>
653
654 <chapter>
655 <title>Additional resources</title>
656 <section>
657 <title>Off-line resources</title>
658 <body>
659
660 <ul>
661 <li>java-config man page</li>
662 <li><c>java-config --help</c></li>
663 </ul>
664
665 </body>
666 </section>
667 <section>
668 <title>Online resources</title>
669 <body>
670
671 <ul>
672 <li>
673 The <uri link="http://www.gentoo.org/proj/en/java/">Java Project
674 Page</uri>
675 </li>
676 <li>
677 The <uri
678 link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>,
679 <uri
680 link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user</uri>, and
681 <uri
682 link="http://news.gmane.org/gmane.linux.gentoo.devel">gentoo-dev</uri>
683 mailing list archives
684 </li>
685 <li>
686 <uri link="irc://irc.gentoo.org/gentoo">#gentoo</uri> and <uri
687 link="irc://irc.gentoo.org/gentoo-java">#gentoo-java</uri> on IRC
688 </li>
689 <li>
690 <uri
691 link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's
692 entry for Java</uri>
693 </li>
694 <li>
695 If you have suggestions or questions regarding this document, please email
696 the Gentoo Java team: <mail>java@gentoo.org</mail>
697 </li>
698 </ul>
699
700 </body>
701 </section>
702 </chapter>
703 </guide>

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