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Mon May 9 21:36:03 2011 UTC (3 years, 4 months ago) by nightmorph
Branch: MAIN
Changes since 1.50: +4 -31 lines
File MIME type: application/xml
correct category for icedtea6-bin, remove icedtea since it's only ~arch, remove chapter referencing outdated /proj/en/java/java-upgrade, bug 366257 and bug 366645

1 <?xml version="1.0" encoding="UTF-8"?>
2 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/java.xml,v 1.50 2011/05/09 19:16:31 nightmorph Exp $ -->
4
5 <guide>
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>2</version>
28 <date>2011-05-09</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>Installing a Virtual Machine</title>
61 <section>
62 <title>The choices</title>
63 <body>
64
65 <p>
66 Gentoo provides numerous Runtime Environments (JREs) and Development Kits
67 (JDKs). Among the current choices, we have:
68 </p>
69
70 <table>
71 <tr>
72 <th>Vendor</th>
73 <th>JDK</th>
74 <th>JRE</th>
75 </tr>
76 <tr>
77 <ti>Sun's Java Kit</ti>
78 <ti>dev-java/sun-jdk</ti>
79 <ti>dev-java/sun-jre-bin</ti>
80 </tr>
81 <tr>
82 <ti>The IBM Java Kit</ti>
83 <ti>dev-java/ibm-jdk-bin</ti>
84 <ti>dev-java/ibm-jre-bin</ti>
85 </tr>
86 <tr>
87 <ti>BEA WebLogic's J2SE Development Kit</ti>
88 <ti>dev-java/jrockit-jdk-bin</ti>
89 </tr>
90 <tr>
91 <ti>The IcedTea Open Java Kit</ti>
92 <ti>dev-java/icedtea6-bin</ti>
93 </tr>
94 </table>
95
96 <!--
97 TODO: list free implementations?
98 note about not drop-in replacements
99 kaffe/sablevm/gcj/jamvm
100 -->
101 </body>
102 </section>
103 <section>
104 <title>Installing a JRE/JDKs</title>
105 <body>
106
107 <p>
108 To install your profile's default JDK, you can run <c>emerge virtual/jdk</c>.
109 Or to install your profile's default JRE, you can <c>emerge virtual/jre</c>.
110 </p>
111
112 <p>
113 Some JDKs and JREs, including the Sun packages, require accepting an End User
114 License Agreement, or EULA. If its license (such as dlj-1.1) is not listed in
115 ACCEPT_LICENSE in <path>/etc/make.conf</path>, then you won't be able to install
116 the JDK/JRE. For more information on how to add acceptable licenses to
117 <path>make.conf</path>, please read the <uri
118 link="/doc/en/handbook/handbook-x86.xml?part=2&amp;chap=1#doc_chap4">Portage
119 Handbook</uri>.
120 </p>
121
122 <p>
123 To avoid any restrictive license hassle, consider installing
124 <c>icedtea6-bin</c>, which is an open Java implementation from the OpenJDK
125 project.
126 </p>
127
128 <note>
129 A JDK also includes a JRE, so if you install a JDK you shouldn't have to also
130 have to install a JRE.
131 </note>
132
133 </body>
134 </section>
135 <section>
136 <title>Installing fetch-restricted virtual machines</title>
137 <body>
138
139 <p>
140 Some of the JDKs and JREs require you to jump through a few hoops before
141 installing. Simply emerge the packages as you normally would. The ebuilds will
142 then instruct you where to go and what to download.
143 </p>
144
145 <p>
146 You should download the indicated file(s) into
147 <path>/usr/portage/distfiles</path>. Once there, you can rerun the emerge
148 command, at which point the JRE/JDK will be begin to install.
149 </p>
150
151 </body>
152 </section>
153 </chapter>
154
155 <chapter>
156 <title>Configuring your virtual machine</title>
157 <section>
158 <title>Overview</title>
159 <body>
160
161 <p>
162 Gentoo has the ability to have multiple JDKs and JREs installed without causing
163 conflicts.
164 </p>
165
166 <p>
167 Using the <c>java-config</c> tool, you can set the system-wide default
168 (provided you have root access). Users can also use <c>java-config</c> to set
169 up their own personal default.
170 </p>
171
172 <note>
173 You can also use <e>eselect</e> to change the system and user vm. See
174 <c>eselect java-vm help</c>.
175 </note>
176
177 </body>
178 </section>
179 <section>
180 <title>Setting a default virtual machine</title>
181 <body>
182
183 <p>
184 Running the command <c>java-config --list-available-vms</c> will give you a
185 list of all JREs and JDKs installed on your system. Here is an example of
186 output:
187 </p>
188
189 <pre caption="Listing available VMs">
190 # <i>java-config --list-available-vms</i>
191 The following VMs are available for generation-2:
192 1) IcedTea6-bin 1.4.1 [icedtea6-bin]
193 2) Sun JDK 1.5.0.20 [sun-jdk-1.5] <comment>(Build Only)</comment>
194 *) Sun JDK 1.6.0.16 [sun-jdk-1.6]
195 </pre>
196
197 <note>
198 VMs marked as Build Only may contain security vulnerabilities and/or be EOL.
199 Gentoo recommends not setting these VMs as either your system or user VM.
200 Please see <uri link="java.xml#build-only">Build Only VM</uri> for more
201 information.
202 </note>
203
204 <p>
205 The <e>*</e> indicates this is the current active vm (system-vm or user-vm when
206 set). The name in the brackets (<e>[]</e>) is the handle or ID for that
207 particular VM. You use the handle or the number to <c>java-config
208 --set-system-vm</c>. Here is an example of how to set the system VM.
209 </p>
210
211 <pre caption="Setting the System VM">
212 <comment>(By handle (preferred))</comment>
213 # <i>java-config --set-system-vm sun-jdk-1.6</i>
214 Now using sun-jdk-1.6 as your generation-2 system JVM
215 <comment>(By number)</comment>
216 # <i>java-config --set-system-vm 3</i>
217 Now using sun-jdk-1.6 as your generation-2 system JVM
218 </pre>
219
220 <p>
221 As a regular user, you can use <c>java-config --set-user-vm</c>.
222 </p>
223
224 <note>
225 You no longer have to <c>source</c> the profile for updates to the user/system
226 VM take place.
227 </note>
228
229 </body>
230 </section>
231 <section id="build-only">
232 <title>Build Only VM</title>
233 <body>
234
235 <p>
236 Some virtual machines are flagged as build-only due to being EOL and/or
237 containing security vulnerabilities. These virtual machines will not
238 automatically be used by Gentoo for the running of applications using Gentoo
239 launchers but will still be available for use by Gentoo's build environment as
240 some packages may require them for building. The setting of these virtual
241 machines as either your system or user VM is strongly discouraged as these VMs
242 will then be used when running the <path>/usr/bin/{java,javac,..}</path>
243 executables and will also be used by any packages not using Gentoo's launcher
244 scripts.
245 </p>
246
247 </body>
248 </section>
249 <section id="preferred-vm">
250 <title>Preferred Build VM</title>
251 <body>
252
253 <p>
254 While merging Java packages, the VM used for building can sometimes be different
255 from the one currently set as the system VM.
256 </p>
257
258 <p>
259 This merge time VM switching is needed when, for example, your system-vm is
260 set to a 1.6 VM and the package you are merging requires a 1.5 VM. While merging
261 it will select and use a 1.5 VM, leaving your system-vm choice intact.
262 </p>
263
264 <p>
265 To define which VM is selected when a switch is needed, we have created a list of <e>default/supported
266 VMs</e> per arch. You can find them in
267 <path>/usr/share/java-config-2/config/jdk-defaults.conf</path>.
268 </p>
269
270 <p>
271 You can override these defaults (and even your selected system VM) in
272 <path>/etc/java-config-2/build/jdk.conf</path> and have complete control over
273 which VM will get used for merging. Some examples:
274 </p>
275
276 <pre caption="Example /etc/java-config-2/build/jdk.conf">
277 <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>
278 *=sun-jdk
279 </pre>
280
281 <pre caption="Example /etc/java-config-2/build/jdk.conf">
282 <comment>(Always use sun-jdk-1.5 wherever possible, except for when a 1.4 or 1.3 VM is explicitly required)</comment>
283 *=sun-jdk-1.5
284 </pre>
285
286 <pre caption="Example /etc/java-config-2/build/jdk.conf">
287 <comment># For 1.3 I prefer sun-jdk 1.4 but when it is not available, use ibm-jdk-bin,
288 # For 1.5, use sun-jdk </comment>
289 1.3=sun-jdk-1.4 ibm-jdk-bin
290 1.5=sun-jdk
291 </pre>
292
293 <warn>
294 You do not <e>have</e> to edit this file. If you change these options to use a
295 unsupported VM, things could possibly break. Because of the wide variety of
296 available VMs, we do not have the resources to test and verify every package
297 works on all of them. Bugs reported with a unsupported VM won't be prioritized
298 as much as bugs present within supported VMs.
299 </warn>
300
301 </body>
302 </section>
303 </chapter>
304
305 <chapter>
306 <title>Compilers</title>
307 <section>
308 <body>
309
310 <p>
311 The standard Java compiler used for building is <c>javac</c>, which comes with
312 each JDK. In addition to configuring the VM used at build time, it is also
313 possible configure which compiler is used. Essentially, you define a list your
314 preference for which compiler to use in
315 <path>/etc/java-config-2/build/compilers.conf</path>.
316 </p>
317
318 <pre caption="/etc/java-config-2/build/compilers.conf">
319 # If the ebuild supports it
320 # it will check the COMPILERS var front to back and
321 # use the first compiler that is installed
322
323 COMPILERS="ecj-X.Y jikes javac"
324 </pre>
325
326 <p>
327 Some compilers don't support all possible -target and -source arguments.
328 Therefore, each compiler in the list is checked to see if it can support the
329 desired -source/-target. javac will work in all cases, so if no other suitable
330 compiler is found, it will be used instead.
331 </p>
332
333 <p>
334 More details about each compiler are provided below:
335 </p>
336
337 <table>
338 <tr>
339 <th>Name</th>
340 <th>Handle</th>
341 <th>Package</th>
342 <th>Description</th>
343 </tr>
344 <tr>
345 <ti>javac</ti>
346 <ti>javac</ti>
347 <ti>N/A</ti>
348 <ti>
349 This is the default compiler that will be used, and comes with each JDK.
350 </ti>
351 </tr>
352 <tr>
353 <ti>jikes</ti>
354 <ti>jikes</ti>
355 <ti>dev-java/jikes</ti>
356 <ti>
357 Jikes was originally developed by IBM. Anecdotally, it is generally quicker
358 than javac. Note however, that it is more pedantic, and will fail under a
359 few circumstances where javac has no issue. It also does not support Java
360 1.5 syntax yet.
361 </ti>
362 </tr>
363 <tr>
364 <ti>Eclipse Compiler for Java</ti>
365 <ti>ecj</ti>
366 <ti>dev-java/eclipse-ecj</ti>
367 <ti>
368 ECJ is the compiler used by the Eclipse software development kit. It is
369 very full featured, and is pretty fast. It does support Java 1.5 syntax.
370 </ti>
371 </tr>
372 </table>
373
374 </body>
375 </section>
376 </chapter>
377
378 <chapter>
379 <title>Setting a default CLASSPATH</title>
380 <section>
381 <body>
382
383 <warn>
384 The options explained in this section should be considered deprecated and will
385 most likely be removed in the future. We strongly recommend against using
386 these, because your Java projects or application should ideally manage their
387 own classpaths. If you choose to specify a default CLASSPATH, some applications
388 may behave unexpectedly, because classes they weren't expecting would be on the
389 classpath.
390 </warn>
391
392 <p>
393 <c>java-config</c> can also be used to set a system-wide default CLASSPATH, as
394 well a user-specific default CLASSPATH.
395 </p>
396
397 <p>
398 First, you will want to list available Java libraries installed on your system
399 that might want to be put in your CLASSPATH. Here is an example of output:
400 </p>
401
402 <pre caption="Listing classes">
403 # <i>java-config --list-available-packages</i>
404 [xerces-2] The next generation of high performance, fully compliant XML parsers in the Apache Xerces family (/usr/share/xerces-2/package.env)
405 [junit] Simple framework to write repeatable tests (/usr/share/junit/package.env)
406 [bsh] BeanShell: A small embeddable Java source interpreter (/usr/share/bsh/package.env)
407 [bcel] The Byte Code Engineering Library: analyze, create, manipulate Java class files (/usr/share/bcel/package.env)
408 [log4j] A low-overhead robust logging package for Java (/usr/share/log4j/package.env)
409 ...
410 </pre>
411
412 <p>
413 Again, the names in brackets (<e>[]</e>) are the IDs that you have to pass to
414 <c>java-config --set-system-classpath</c>. Here is an example:
415 </p>
416
417 <pre caption="Setting classpaths">
418 # <i>java-config --set-system-classpath log4j,xerces-2</i>
419 </pre>
420
421 <note>
422 The current directory (<path>.</path>) will not be part of the system
423 classpath, as that should be added in your system's login profile.
424 </note>
425
426 <p>
427 You will have to update your environment by logging out, then in again or
428 sourcing <path>/etc/profile</path>.
429 </p>
430
431 <p>
432 For users, <c>java-config --set-user-classpath</c> will create
433 <path>~/.gentoo/java-env-classpath</path>, which you should then source from
434 your shell's profile.
435 </p>
436
437 <pre caption="Sourcing user specific classpath">
438 <i>if [[ -f "${HOME}/.gentoo/java-env-classpath" ]]; then
439 source ${HOME}/.gentoo/java-env-classpath
440 fi</i>
441 </pre>
442
443 <p>
444 If you really want a system wide or user default classpath you can add
445 something like the following to your shell's profile. But we would advise
446 against it.
447 </p>
448
449 <pre caption="Setting classpath">
450 # <i>export CLASSPATH="${CLASSPATH}:$(java-config --classpath log4j,xerces-2)"</i>
451 </pre>
452
453 </body>
454 </section>
455 </chapter>
456
457 <chapter>
458 <title>Java Browser Plugins</title>
459 <section>
460 <title>Installing a plugin</title>
461 <body>
462
463 <p>
464 You can install a Java plugin for your web browser by emerging a Java VM with
465 the <c>nsplugin</c> USE flag set.
466 </p>
467
468 <note>
469 <c>nsplugin</c> is not available for all architectures. Check for available
470 plugins on your arch before trying to install a VM by running <c>emerge -pv
471 &lt;java-vm&gt;</c>.
472 </note>
473
474 <p>
475 Portage will allow you to install multiple versions of Java plugins, though
476 only one will be used by your browser. You can check the list of available
477 plugins by running:
478 </p>
479
480 <pre caption="Viewing available plugins">
481 # <i>eselect java-nsplugin list</i>
482 [1] sun-jre-bin-1.6
483 [2] icedtea6-bin
484 </pre>
485
486 <p>
487 In this example, <c>sun-jre-bin</c> is selected for the browser plugin.
488 </p>
489
490 <pre caption="Selecting a plugin">
491 # <i>eselect java-nsplugin set sun-jre-bin-1.6</i>
492 </pre>
493
494 <p>
495 Verify that the correct plugin was selected:
496 </p>
497
498 <pre caption="Verifying the correct plugin">
499 # <i>eselect java-nsplugin list</i>
500 [1] sun-jre-bin-1.6 current
501 [2] icedtea6-bin
502 </pre>
503
504 <p>
505 Java.com also provides a link to <uri
506 link="http://java.com/en/download/installed.jsp">verify your installed
507 plugin</uri>. Additionally, if you are using a Mozilla-based browser, you can
508 verify your Java plugin by typing <c>about:plugins</c> into the address bar.
509 </p>
510
511 </body>
512 </section>
513 <section>
514 <title>Plugins on multilib systems</title>
515 <body>
516
517 <p>
518 If you are running a mixed 64-bit and 32-bit multilib system (for example, on
519 AMD64), you can use 64-bit and 32-bit Java plugins. Unless you have a pressing
520 need to run 32-bit Java applications, we recommend using native 64-bit plugins
521 on 64-bit web browsers.
522 </p>
523
524 <p>
525 There are several native 64-bit browser plugins available. The default JDK/JRE
526 pair, <c>sun-jdk</c> and <c>sun-jre-bin</c>, both include browser plugins. Just
527 emerge one of them with the <c>nsplugin</c> USE flag enabled.
528 </p>
529
530 <pre caption="Installing a 64-bit plugin">
531 # <i>echo "dev-java/sun-jre-bin nsplugin" >> /etc/portage/package.use</i>
532 # <i>emerge sun-jre-bin</i>
533 </pre>
534
535 <p>
536 To use a 32-bit plugin on a 32-bit browser, you will need to emerge
537 <c>emul-linux-x86-java</c> with the <c>nsplugin</c> USE flag enabled.
538 </p>
539
540 <pre caption="Installing a 32-bit plugin">
541 # <i>echo "app-emulation/emul-linux-x86-java nsplugin" >> /etc/portage/package.use</i>
542 # <i>emerge emul-linux-x86-java</i>
543 </pre>
544
545 <p>
546 Next, check which plugins are available:
547 </p>
548
549 <pre caption="Viewing available plugins">
550 # <i>eselect java-nsplugin list</i>
551 Available 32-bit Java browser plugins
552 [1] emul-linux-x86-java-1.5
553 [2] emul-linux-x86-java-1.6
554 Available 64-bit Java browser plugins
555 [1] icedtea6-bin
556 [2] sun-jre-bin-1.6
557 </pre>
558
559 <p>
560 Now select the right plugin for your browsers:
561 </p>
562
563 <pre caption="Selecting plugins">
564 <comment>(Choose the plugins for 32-bit and 64-bit browsers)</comment>
565 # <i>eselect java-nsplugin set 32bit emul-linux-x86-java-1.6</i>
566 # <i>eselect java-nsplugin set 64bit sun-jre-bin-1.6</i>
567 </pre>
568
569 <p>
570 Verify the correct plugin was selected:
571 </p>
572
573 <pre caption="Verifying the correct plugin">
574 # <i>eselect java-nsplugin list</i>
575 Available 32-bit Java browser plugins
576 [1] emul-linux-x86-java-1.5
577 [2] emul-linux-x86-java-1.6 current
578 Available 64-bit Java browser plugins
579 [1] icedtea6-bin
580 [2] sun-jre-bin-1.6 current
581 </pre>
582
583 </body>
584 </section>
585 </chapter>
586
587 <chapter>
588 <title>USE flags for use with Java</title>
589 <section>
590 <title>Setting USE flags</title>
591 <body>
592
593 <p>
594 For more information regarding USE flags, refer to the <uri
595 link="/doc/en/handbook/handbook-x86.xml?part=2&amp;chap=2">USE flags</uri>
596 chapter from the Gentoo Handbook.
597 </p>
598
599 </body>
600 </section>
601 <section>
602 <title>The flags</title>
603 <body>
604
605 <ul>
606 <li>The <b>java</b> flag adds support for Java in a variety of programs</li>
607 <li>
608 The <b>nsplugin</b> flag adds support for Mozilla-like browsers (including
609 Firefox). You will need this for viewing Java applets in your Mozilla-like
610 browser.
611 </li>
612 <li>
613 The <b>source</b> flag installs a zip of the source code of a package.
614 This is traditionally used for IDEs to 'attach' source to the libraries you
615 are using.
616 </li>
617 <li>The <b>jce</b> flag adds support for the Java Cryptography Engine</li>
618 <li>
619 For Java packages, the <b>doc</b> flag will build API documentation using
620 javadoc.
621 </li>
622 </ul>
623
624 </body>
625 </section>
626 </chapter>
627
628 <chapter>
629 <title>Additional resources</title>
630 <section>
631 <title>Off-line resources</title>
632 <body>
633
634 <ul>
635 <li>java-config man page</li>
636 <li><c>java-config --help</c></li>
637 </ul>
638
639 </body>
640 </section>
641 <section>
642 <title>Online resources</title>
643 <body>
644
645 <ul>
646 <li>
647 The <uri link="http://www.gentoo.org/proj/en/java/">Java Project
648 Page</uri>
649 </li>
650 <li>
651 The <uri
652 link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>,
653 <uri
654 link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user</uri>, and
655 <uri
656 link="http://news.gmane.org/gmane.linux.gentoo.devel">gentoo-dev</uri>
657 mailing list archives
658 </li>
659 <li>
660 <uri link="irc://irc.gentoo.org/gentoo">#gentoo</uri> and <uri
661 link="irc://irc.gentoo.org/gentoo-java">#gentoo-java</uri> on IRC
662 </li>
663 <li>
664 <uri
665 link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's
666 entry for Java</uri>
667 </li>
668 <li>
669 If you have suggestions or questions regarding this document, please email
670 the Gentoo Java team: <mail>java@gentoo.org</mail>
671 </li>
672 </ul>
673
674 </body>
675 </section>
676 </chapter>
677 </guide>

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