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Further fix bug #388973 - Updates on java VMs. Nightmorph already made the change on icedtea6-bin, this is the remainder of the patch as offered by Vlastimil Babka

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 1.52 2011/11/08 23:38:12 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>4</version>
28 <date>2011-11-15</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>The IcedTea Open Java SE (formerly icedtea6-bin)</ti>
78 <ti>dev-java/icedtea-bin</ti>
79 <ti />
80 </tr>
81 <tr>
82 <ti>Oracle's Java 7 SE</ti>
83 <ti>dev-java/oracle-jdk-bin</ti>
84 <ti>dev-java/oracle-jre-bin</ti>
85 </tr>
86 <tr>
87 <ti>Sun's Java 6 SE</ti>
88 <ti>dev-java/sun-jdk</ti>
89 <ti>dev-java/sun-jre-bin</ti>
90 </tr>
91 <tr>
92 <ti>The IBM Java SE</ti>
93 <ti>dev-java/ibm-jdk-bin</ti>
94 <ti>dev-java/ibm-jre-bin</ti>
95 </tr>
96 </table>
97
98 <!--
99 TODO: list free implementations?
100 note about not drop-in replacements
101 kaffe/sablevm/gcj/jamvm
102 -->
103 </body>
104 </section>
105 <section>
106 <title>Installing a JRE/JDKs</title>
107 <body>
108
109 <p>
110 To install your profile's default JDK, you can run <c>emerge virtual/jdk</c>.
111 Or to install your profile's default JRE, you can <c>emerge virtual/jre</c>.
112 </p>
113
114 <p>
115 Some JDKs and JREs, including the Sun packages, require accepting an End User
116 License Agreement, or EULA. If its license (such as dlj-1.1) is not listed in
117 ACCEPT_LICENSE in <path>/etc/make.conf</path>, then you won't be able to install
118 the JDK/JRE. For more information on how to add acceptable licenses to
119 <path>make.conf</path>, please read the <uri
120 link="/doc/en/handbook/handbook-x86.xml?part=2&amp;chap=1#doc_chap4">Portage
121 Handbook</uri>.
122 </p>
123
124 <p>
125 To avoid any restrictive license hassle, consider installing
126 <c>icedtea-bin</c>, which is an open Java implementation from the OpenJDK
127 project.
128 </p>
129
130 <note>
131 A JDK also includes a JRE, so if you install a JDK you shouldn't have to also
132 have to install a JRE.
133 </note>
134
135 </body>
136 </section>
137 <section>
138 <title>Installing fetch-restricted virtual machines</title>
139 <body>
140
141 <p>
142 Some of the JDKs and JREs require you to jump through a few hoops before
143 installing. Simply emerge the packages as you normally would. The ebuilds will
144 then instruct you where to go and what to download.
145 </p>
146
147 <p>
148 You should download the indicated file(s) into
149 <path>/usr/portage/distfiles</path>. Once there, you can rerun the emerge
150 command, at which point the JRE/JDK will be begin to install.
151 </p>
152
153 </body>
154 </section>
155 </chapter>
156
157 <chapter>
158 <title>Configuring your virtual machine</title>
159 <section>
160 <title>Overview</title>
161 <body>
162
163 <p>
164 Gentoo has the ability to have multiple JDKs and JREs installed without causing
165 conflicts.
166 </p>
167
168 <p>
169 Using the <c>java-config</c> tool, you can set the system-wide default
170 (provided you have root access). Users can also use <c>java-config</c> to set
171 up their own personal default.
172 </p>
173
174 <note>
175 You can also use <e>eselect</e> to change the system and user vm. See
176 <c>eselect java-vm help</c>.
177 </note>
178
179 </body>
180 </section>
181 <section>
182 <title>Setting a default virtual machine</title>
183 <body>
184
185 <p>
186 Running the command <c>java-config --list-available-vms</c> will give you a
187 list of all JREs and JDKs installed on your system. Here is an example of
188 output:
189 </p>
190
191 <pre caption="Listing available VMs">
192 # <i>java-config --list-available-vms</i>
193 The following VMs are available for generation-2:
194 1) IcedTea-bin 1.10.4 [icedtea-bin]
195 2) Sun JDK 1.5.0.20 [sun-jdk-1.5] <comment>(Build Only)</comment>
196 *) Sun JDK 1.6.0.16 [sun-jdk-1.6]
197 </pre>
198
199 <note>
200 VMs marked as Build Only may contain security vulnerabilities and/or be EOL.
201 Gentoo recommends not setting these VMs as either your system or user VM.
202 Please see <uri link="java.xml#build-only">Build Only VM</uri> for more
203 information.
204 </note>
205
206 <p>
207 The <e>*</e> indicates this is the current active vm (system-vm or user-vm when
208 set). The name in the brackets (<e>[]</e>) is the handle or ID for that
209 particular VM. You use the handle or the number to <c>java-config
210 --set-system-vm</c>. Here is an example of how to set the system VM.
211 </p>
212
213 <pre caption="Setting the System VM">
214 <comment>(By handle (preferred))</comment>
215 # <i>java-config --set-system-vm sun-jdk-1.6</i>
216 Now using sun-jdk-1.6 as your generation-2 system JVM
217 <comment>(By number)</comment>
218 # <i>java-config --set-system-vm 3</i>
219 Now using sun-jdk-1.6 as your generation-2 system JVM
220 </pre>
221
222 <p>
223 As a regular user, you can use <c>java-config --set-user-vm</c>.
224 </p>
225
226 <note>
227 You no longer have to <c>source</c> the profile for updates to the user/system
228 VM take place.
229 </note>
230
231 </body>
232 </section>
233 <section id="build-only">
234 <title>Build Only VM</title>
235 <body>
236
237 <p>
238 Some virtual machines are flagged as build-only due to being EOL and/or
239 containing security vulnerabilities. These virtual machines will not
240 automatically be used by Gentoo for the running of applications using Gentoo
241 launchers but will still be available for use by Gentoo's build environment as
242 some packages may require them for building. The setting of these virtual
243 machines as either your system or user VM is strongly discouraged as these VMs
244 will then be used when running the <path>/usr/bin/{java,javac,..}</path>
245 executables and will also be used by any packages not using Gentoo's launcher
246 scripts.
247 </p>
248
249 </body>
250 </section>
251 <section id="preferred-vm">
252 <title>Preferred Build VM</title>
253 <body>
254
255 <p>
256 While merging Java packages, the VM used for building can sometimes be different
257 from the one currently set as the system VM.
258 </p>
259
260 <p>
261 This merge time VM switching is needed when, for example, your system-vm is
262 set to a 1.6 VM and the package you are merging requires a 1.5 VM. While merging
263 it will select and use a 1.5 VM, leaving your system-vm choice intact.
264 </p>
265
266 <p>
267 To define which VM is selected when a switch is needed, we have created a list of <e>default/supported
268 VMs</e> per arch. You can find them in
269 <path>/usr/share/java-config-2/config/jdk-defaults.conf</path>.
270 </p>
271
272 <p>
273 You can override these defaults (and even your selected system VM) in
274 <path>/etc/java-config-2/build/jdk.conf</path> and have complete control over
275 which VM will get used for merging. Some examples:
276 </p>
277
278 <pre caption="Example /etc/java-config-2/build/jdk.conf">
279 <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>
280 *=sun-jdk
281 </pre>
282
283 <pre caption="Example /etc/java-config-2/build/jdk.conf">
284 <comment>(Always use sun-jdk-1.5 wherever possible, except for when a 1.4 or 1.3 VM is explicitly required)</comment>
285 *=sun-jdk-1.5
286 </pre>
287
288 <pre caption="Example /etc/java-config-2/build/jdk.conf">
289 <comment># For 1.3 I prefer sun-jdk 1.4 but when it is not available, use ibm-jdk-bin,
290 # For 1.5, use sun-jdk </comment>
291 1.3=sun-jdk-1.4 ibm-jdk-bin
292 1.5=sun-jdk
293 </pre>
294
295 <warn>
296 You do not <e>have</e> to edit this file. If you change these options to use a
297 unsupported VM, things could possibly break. Because of the wide variety of
298 available VMs, we do not have the resources to test and verify every package
299 works on all of them. Bugs reported with a unsupported VM won't be prioritized
300 as much as bugs present within supported VMs.
301 </warn>
302
303 </body>
304 </section>
305 </chapter>
306
307 <chapter>
308 <title>Compilers</title>
309 <section>
310 <body>
311
312 <p>
313 The standard Java compiler used for building is <c>javac</c>, which comes with
314 each JDK. In addition to configuring the VM used at build time, it is also
315 possible configure which compiler is used. Essentially, you define a list your
316 preference for which compiler to use in
317 <path>/etc/java-config-2/build/compilers.conf</path>.
318 </p>
319
320 <pre caption="/etc/java-config-2/build/compilers.conf">
321 # If the ebuild supports it
322 # it will check the COMPILERS var front to back and
323 # use the first compiler that is installed
324
325 COMPILERS="ecj-X.Y jikes javac"
326 </pre>
327
328 <p>
329 Some compilers don't support all possible -target and -source arguments.
330 Therefore, each compiler in the list is checked to see if it can support the
331 desired -source/-target. javac will work in all cases, so if no other suitable
332 compiler is found, it will be used instead.
333 </p>
334
335 <p>
336 More details about each compiler are provided below:
337 </p>
338
339 <table>
340 <tr>
341 <th>Name</th>
342 <th>Handle</th>
343 <th>Package</th>
344 <th>Description</th>
345 </tr>
346 <tr>
347 <ti>javac</ti>
348 <ti>javac</ti>
349 <ti>N/A</ti>
350 <ti>
351 This is the default compiler that will be used, and comes with each JDK.
352 </ti>
353 </tr>
354 <tr>
355 <ti>jikes</ti>
356 <ti>jikes</ti>
357 <ti>dev-java/jikes</ti>
358 <ti>
359 Jikes was originally developed by IBM. Anecdotally, it is generally quicker
360 than javac. Note however, that it is more pedantic, and will fail under a
361 few circumstances where javac has no issue. It also does not support Java
362 1.5 syntax yet.
363 </ti>
364 </tr>
365 <tr>
366 <ti>Eclipse Compiler for Java</ti>
367 <ti>ecj</ti>
368 <ti>dev-java/eclipse-ecj</ti>
369 <ti>
370 ECJ is the compiler used by the Eclipse software development kit. It is
371 very full featured, and is pretty fast. It does support Java 1.5 syntax.
372 </ti>
373 </tr>
374 </table>
375
376 </body>
377 </section>
378 </chapter>
379
380 <chapter>
381 <title>Setting a default CLASSPATH</title>
382 <section>
383 <body>
384
385 <warn>
386 The options explained in this section should be considered deprecated and will
387 most likely be removed in the future. We strongly recommend against using
388 these, because your Java projects or application should ideally manage their
389 own classpaths. If you choose to specify a default CLASSPATH, some applications
390 may behave unexpectedly, because classes they weren't expecting would be on the
391 classpath.
392 </warn>
393
394 <p>
395 <c>java-config</c> can also be used to set a system-wide default CLASSPATH, as
396 well a user-specific default CLASSPATH.
397 </p>
398
399 <p>
400 First, you will want to list available Java libraries installed on your system
401 that might want to be put in your CLASSPATH. Here is an example of output:
402 </p>
403
404 <pre caption="Listing classes">
405 # <i>java-config --list-available-packages</i>
406 [xerces-2] The next generation of high performance, fully compliant XML parsers in the Apache Xerces family (/usr/share/xerces-2/package.env)
407 [junit] Simple framework to write repeatable tests (/usr/share/junit/package.env)
408 [bsh] BeanShell: A small embeddable Java source interpreter (/usr/share/bsh/package.env)
409 [bcel] The Byte Code Engineering Library: analyze, create, manipulate Java class files (/usr/share/bcel/package.env)
410 [log4j] A low-overhead robust logging package for Java (/usr/share/log4j/package.env)
411 ...
412 </pre>
413
414 <p>
415 Again, the names in brackets (<e>[]</e>) are the IDs that you have to pass to
416 <c>java-config --set-system-classpath</c>. Here is an example:
417 </p>
418
419 <pre caption="Setting classpaths">
420 # <i>java-config --set-system-classpath log4j,xerces-2</i>
421 </pre>
422
423 <note>
424 The current directory (<path>.</path>) will not be part of the system
425 classpath, as that should be added in your system's login profile.
426 </note>
427
428 <p>
429 You will have to update your environment by logging out, then in again or
430 sourcing <path>/etc/profile</path>.
431 </p>
432
433 <p>
434 For users, <c>java-config --set-user-classpath</c> will create
435 <path>~/.gentoo/java-env-classpath</path>, which you should then source from
436 your shell's profile.
437 </p>
438
439 <pre caption="Sourcing user specific classpath">
440 <i>if [[ -f "${HOME}/.gentoo/java-env-classpath" ]]; then
441 source ${HOME}/.gentoo/java-env-classpath
442 fi</i>
443 </pre>
444
445 <p>
446 If you really want a system wide or user default classpath you can add
447 something like the following to your shell's profile. But we would advise
448 against it.
449 </p>
450
451 <pre caption="Setting classpath">
452 # <i>export CLASSPATH="${CLASSPATH}:$(java-config --classpath log4j,xerces-2)"</i>
453 </pre>
454
455 </body>
456 </section>
457 </chapter>
458
459 <chapter>
460 <title>Java Browser Plugins</title>
461 <section>
462 <title>Installing a plugin</title>
463 <body>
464
465 <p>
466 You can install a Java plugin for your web browser by emerging a Java VM with
467 the <c>nsplugin</c> USE flag set.
468 </p>
469
470 <note>
471 <c>nsplugin</c> is not available for all architectures. Check for available
472 plugins on your arch before trying to install a VM by running <c>emerge -pv
473 &lt;java-vm&gt;</c>.
474 </note>
475
476 <p>
477 Portage will allow you to install multiple versions of Java plugins, though
478 only one will be used by your browser. You can check the list of available
479 plugins by running:
480 </p>
481
482 <pre caption="Viewing available plugins">
483 # <i>eselect java-nsplugin list</i>
484 [1] sun-jre-bin-1.6
485 [2] icedtea-bin
486 </pre>
487
488 <p>
489 In this example, <c>sun-jre-bin</c> is selected for the browser plugin.
490 </p>
491
492 <pre caption="Selecting a plugin">
493 # <i>eselect java-nsplugin set sun-jre-bin-1.6</i>
494 </pre>
495
496 <p>
497 Verify that the correct plugin was selected:
498 </p>
499
500 <pre caption="Verifying the correct plugin">
501 # <i>eselect java-nsplugin list</i>
502 [1] sun-jre-bin-1.6 current
503 [2] icedtea-bin
504 </pre>
505
506 <p>
507 Java.com also provides a link to <uri
508 link="http://java.com/en/download/installed.jsp">verify your installed
509 plugin</uri>. Additionally, if you are using a Mozilla-based browser, you can
510 verify your Java plugin by typing <c>about:plugins</c> into the address bar.
511 </p>
512
513 </body>
514 </section>
515 <section>
516 <title>Plugins on multilib systems</title>
517 <body>
518
519 <p>
520 If you are running a mixed 64-bit and 32-bit multilib system (for example, on
521 AMD64), you can use 64-bit and 32-bit Java plugins. Unless you have a pressing
522 need to run 32-bit Java applications, we recommend using native 64-bit plugins
523 on 64-bit web browsers.
524 </p>
525
526 <p>
527 There are several native 64-bit browser plugins available. The default JDK/JRE
528 pair, <c>sun-jdk</c> and <c>sun-jre-bin</c>, both include browser plugins. Just
529 emerge one of them with the <c>nsplugin</c> USE flag enabled.
530 </p>
531
532 <pre caption="Installing a 64-bit plugin">
533 # <i>echo "dev-java/sun-jre-bin nsplugin" >> /etc/portage/package.use</i>
534 # <i>emerge sun-jre-bin</i>
535 </pre>
536
537 <p>
538 To use a 32-bit plugin on a 32-bit browser, you will need to emerge
539 <c>emul-linux-x86-java</c> with the <c>nsplugin</c> USE flag enabled.
540 </p>
541
542 <pre caption="Installing a 32-bit plugin">
543 # <i>echo "app-emulation/emul-linux-x86-java nsplugin" >> /etc/portage/package.use</i>
544 # <i>emerge emul-linux-x86-java</i>
545 </pre>
546
547 <p>
548 Next, check which plugins are available:
549 </p>
550
551 <pre caption="Viewing available plugins">
552 # <i>eselect java-nsplugin list</i>
553 Available 32-bit Java browser plugins
554 [1] emul-linux-x86-java-1.5
555 [2] emul-linux-x86-java-1.6
556 Available 64-bit Java browser plugins
557 [1] icedtea-bin
558 [2] sun-jre-bin-1.6
559 </pre>
560
561 <p>
562 Now select the right plugin for your browsers:
563 </p>
564
565 <pre caption="Selecting plugins">
566 <comment>(Choose the plugins for 32-bit and 64-bit browsers)</comment>
567 # <i>eselect java-nsplugin set 32bit emul-linux-x86-java-1.6</i>
568 # <i>eselect java-nsplugin set 64bit sun-jre-bin-1.6</i>
569 </pre>
570
571 <p>
572 Verify the correct plugin was selected:
573 </p>
574
575 <pre caption="Verifying the correct plugin">
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 current
580 Available 64-bit Java browser plugins
581 [1] icedtea-bin
582 [2] sun-jre-bin-1.6 current
583 </pre>
584
585 </body>
586 </section>
587 </chapter>
588
589 <chapter>
590 <title>USE flags for use with Java</title>
591 <section>
592 <title>Setting USE flags</title>
593 <body>
594
595 <p>
596 For more information regarding USE flags, refer to the <uri
597 link="/doc/en/handbook/handbook-x86.xml?part=2&amp;chap=2">USE flags</uri>
598 chapter from the Gentoo Handbook.
599 </p>
600
601 </body>
602 </section>
603 <section>
604 <title>The flags</title>
605 <body>
606
607 <ul>
608 <li>The <b>java</b> flag adds support for Java in a variety of programs</li>
609 <li>
610 The <b>nsplugin</b> flag adds support for Mozilla-like browsers (including
611 Firefox). You will need this for viewing Java applets in your Mozilla-like
612 browser.
613 </li>
614 <li>
615 The <b>source</b> flag installs a zip of the source code of a package.
616 This is traditionally used for IDEs to 'attach' source to the libraries you
617 are using.
618 </li>
619 <li>The <b>jce</b> flag adds support for the Java Cryptography Engine</li>
620 <li>
621 For Java packages, the <b>doc</b> flag will build API documentation using
622 javadoc.
623 </li>
624 </ul>
625
626 </body>
627 </section>
628 </chapter>
629
630 <chapter>
631 <title>Additional resources</title>
632 <section>
633 <title>Off-line resources</title>
634 <body>
635
636 <ul>
637 <li>java-config man page</li>
638 <li><c>java-config --help</c></li>
639 </ul>
640
641 </body>
642 </section>
643 <section>
644 <title>Online resources</title>
645 <body>
646
647 <ul>
648 <li>
649 The <uri link="http://www.gentoo.org/proj/en/java/">Java Project
650 Page</uri>
651 </li>
652 <li>
653 The <uri
654 link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>,
655 <uri
656 link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user</uri>, and
657 <uri
658 link="http://news.gmane.org/gmane.linux.gentoo.devel">gentoo-dev</uri>
659 mailing list archives
660 </li>
661 <li>
662 <uri link="irc://irc.gentoo.org/gentoo">#gentoo</uri> and <uri
663 link="irc://irc.gentoo.org/gentoo-java">#gentoo-java</uri> on IRC
664 </li>
665 <li>
666 <uri
667 link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's
668 entry for Java</uri>
669 </li>
670 <li>
671 If you have suggestions or questions regarding this document, please email
672 the Gentoo Java team: <mail>java@gentoo.org</mail>
673 </li>
674 </ul>
675
676 </body>
677 </section>
678 </chapter>
679 </guide>

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