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1 neysx 1.11 <?xml version="1.0" encoding="UTF-8"?>
2 nightmorph 1.24 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/java.xml,v 1.23 2006/06/24 18:28:06 nightmorph Exp $ -->
3 swift 1.8 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4 zhen 1.4
5 neysx 1.11 <guide link="/doc/en/java.xml">
6     <title>Gentoo Java Guide</title>
7    
8 nightmorph 1.23 <author title="Author">
9 neysx 1.11 <mail link="karltk@gentoo.org">Karl Trygve Kalleberg</mail>
10     </author>
11 nightmorph 1.23 <author title="Author">
12     <mail link="nichoj@gentoo.org">Joshua Nichols</mail>
13 neysx 1.11 </author>
14 swift 1.13 <author title="Editor">
15 nightmorph 1.23 <mail link="nightmorph@gentoo.org">Joshua Saddler</mail>
16 swift 1.13 </author>
17 neysx 1.11
18     <abstract>
19 nightmorph 1.23 This guide will introduce you to Java and explain how to use Java with Gentoo
20     Linux.
21 neysx 1.11 </abstract>
22    
23 nightmorph 1.23 <!-- The content of this document is licensed under the CC-BY-SA license -->
24     <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
25 neysx 1.11 <license/>
26    
27 nightmorph 1.23 <version>0.4</version>
28     <date>2006-06-24</date>
29 neysx 1.11
30     <chapter>
31 swift 1.13 <title>What is Java?</title>
32 neysx 1.11 <section>
33     <title>Overview</title>
34     <body>
35    
36     <p>
37 nightmorph 1.23 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 swift 1.13 </p>
46    
47     <p>
48 nightmorph 1.23 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, plug-ins for browsers, among other things. A JDK (Java
51     Development Kit) adds programming tools, such as a bytecode compiler and a
52     debugger.
53 swift 1.13 </p>
54    
55     </body>
56     </section>
57     </chapter>
58    
59     <chapter>
60     <title>Installing a JRE/JDK</title>
61     <section>
62     <title>The choices</title>
63     <body>
64    
65     <p>
66 nightmorph 1.23 Gentoo provides numerous JREs and JDKs. Among the current alternatives, we
67     have:
68 swift 1.13 </p>
69    
70 nightmorph 1.23 <table>
71     <tr>
72     <th>Vendor</th>
73     <th>JDK</th>
74     <th>JRE</th>
75     </tr>
76     <tr>
77     <ti>The Blackdown Java Kit</ti>
78     <ti>dev-java/backdown-jdk</ti>
79     <ti>dev-java/blackdown-jre</ti>
80     </tr>
81     <tr>
82     <ti>Sun's Java Kit</ti>
83     <ti>dev-java/sun-jdk</ti>
84     <ti>dev-java/sun-jre-bin</ti>
85     </tr>
86     <tr>
87     <ti>The IBM Java Kit</ti>
88     <ti>dev-java/ibm-jdk-bin</ti>
89     <ti>dev-java/ibm-jre-bin</ti>
90     </tr>
91     <tr>
92     <ti>The Compaq Java Kit for Alpha/Linux/GNU</ti>
93     <ti>dev-java/compaq-jdk</ti>
94     <ti>dev-java/compaq-jre</ti>
95     </tr>
96     <tr>
97     <ti>BEA WebLogic's J2SE Development Kit</ti>
98     <ti>dev-java/jrockit-jdk-bin</ti>
99     </tr>
100     </table>
101    
102     <!--
103     TODO: list free implmentations?
104     note about not drop-in replacemenets
105     kaffe/sablevm/gcj/jamvm
106     -->
107    
108     <p>
109     The default is Blackdown for both the JRE and the JDK, as it is freely ("free
110     as in beer") available without any registration fuss.
111     </p>
112 swift 1.13
113     <p>
114 nightmorph 1.23 Both the Sun and the IBM are generally faster, but getting them is a bit more
115     hassle, as you are required to read and accept their license before downloading
116     (IBM additionally requires you to register).
117 neysx 1.11 </p>
118    
119     <p>
120 nightmorph 1.23 Our ebuilds for the Sun and IBM JRE/JDKs will inform you how to download the
121     appropriate files.
122 neysx 1.11 </p>
123    
124 nightmorph 1.23 </body>
125     </section>
126     <section>
127     <title>Installing a JRE/JDKs</title>
128     <body>
129    
130 neysx 1.11 <p>
131 nightmorph 1.23 To install your profile's default JDK, you can run <c>emerge virtual/jdk</c>.
132     Or to install your profile's default JRE, you can <c>emerge virtual/jre</c>.
133 neysx 1.11 </p>
134    
135 nightmorph 1.23 <note>
136     A JDK also includes a JRE, so if you install a JDK you shouldn't have to also
137     have to install a JRE.
138     </note>
139    
140 neysx 1.11 </body>
141     </section>
142     <section>
143 swift 1.13 <title>Installing the Sun/IBM JRE/JDKs</title>
144 neysx 1.11 <body>
145    
146     <p>
147 nightmorph 1.23 If you run <c>emerge dev-java/sun-jdk</c> or <c>emerge
148     dev-java/ibm-jdk-bin</c>, you will be notified that you are required to
149     download the actual files yourself. This has to do with license restrictions
150     for the Sun JRE/JDK (online click-wrap license) and registration issues with
151     the IBM JRE/JDK.
152 neysx 1.11 </p>
153    
154     <p>
155     You should download the indicated file(s) into
156 nightmorph 1.23 <path>/usr/portage/distfiles</path>. Once there, you can rerun the emerge
157     command, at which point the JRE/JDK will be begin to install.
158 neysx 1.11 </p>
159    
160     </body>
161     </section>
162     </chapter>
163    
164     <chapter>
165 swift 1.13 <title>Configuring your JRE/JDK</title>
166 neysx 1.11 <section>
167     <title>Overview</title>
168     <body>
169    
170     <p>
171 nightmorph 1.23 Gentoo has the ability to have multiple JDKs and JREs installed without causing
172     conflicts.
173 neysx 1.11 </p>
174    
175     <p>
176 nightmorph 1.23 Using the <c>java-config</c> tool, you can set the system-wide default
177     (provided you have root access). Users can also use <c>java-config</c> to set
178     up their own personal default.
179 neysx 1.11 </p>
180    
181 nightmorph 1.23 <note>
182     You can also use <e>eselect</e> to change the system and user vm. See
183 nightmorph 1.24 <c>eselect java-vm help</c>.
184 nightmorph 1.23 </note>
185    
186 neysx 1.11 </body>
187     </section>
188     <section>
189 swift 1.13 <title>Setting a default JRE/JDK</title>
190 neysx 1.11 <body>
191    
192     <p>
193 nightmorph 1.23 Running the command <c>java-config --list-available-vms</c> will give you a
194     list of all JREs and JDKs installed on your system. Here is an example of
195     output:
196 neysx 1.11 </p>
197    
198     <pre caption="Listing available VMs">
199 neysx 1.12 # <i>java-config --list-available-vms</i>
200 nightmorph 1.23 1) Blackdown JDK 1.3.1 [blackdown-jdk-1.3] (/etc/env.d/java/20blackdown-jdk-1.3)
201     2) Blackdown JDK 1.4.2.02 [blackdown-jdk-1.4] (/etc/env.d/java/20blackdown-jdk-1.4)
202     3) Blackdown JRE 1.4.2.02 [blackdown-jre-1.4] (/etc/env.d/java/20blackdown-jre-1.4)
203     4) IBM JDK 1.4.2 [ibm-jdk-bin-1.4] (/etc/env.d/java/20ibm-jdk-bin-1.4)
204     5) IBM JRE 1.4.2 [ibm-jre-bin-1.4] (/etc/env.d/java/20ibm-jre-bin-1.4)
205     6) WebLogic JRockit 1.4.2.05 [jrockit-jdk-bin-1.4] (/etc/env.d/java/20jrockit-jdk-bin-1.4)
206     7) WebLogic JRockit 1.5.0.03 [jrockit-jdk-bin-1.5] (/etc/env.d/java/20jrockit-jdk-bin-1.5)
207     8) Sun JDK 1.3.1.13 [sun-jdk-1.3] (/etc/env.d/java/20sun-jdk-1.3)
208     9) Sun JDK 1.4.2.09 [sun-jdk-1.4] (/etc/env.d/java/20sun-jdk-1.4)
209     *) Sun JDK 1.5.0.04 [sun-jdk-1.5] (/etc/env.d/java/20sun-jdk-1.5)
210     11) Sun JRE 1.4.2.09 [sun-jre-bin-1.4] (/etc/env.d/java/20sun-jre-bin-1.4)
211     12) Sun JRE 1.5.0.04 [sun-jre-bin-1.5] (/etc/env.d/java/20sun-jre-bin-1.5)
212 neysx 1.11 </pre>
213    
214     <p>
215 nightmorph 1.23 The <e>*</e> indicates this is the current active vm (system-vm or user-vm when
216     set). The name in the brackets (<e>[]</e>) is the handle or ID for that
217     particular VM. You use the handle or the number to <c>java-config
218     --set-system-vm</c>. Here is an example of how to set the system VM.
219 neysx 1.11 </p>
220 zhen 1.4
221 neysx 1.11 <pre caption="Setting the System VM">
222 nightmorph 1.23 <comment>(By handle (preferred))</comment>
223     # <i>java-config --set-system-vm blackdown-jdk-1.4</i>
224     <comment>(By number)</comment>
225     # <i>java-config --set-system-vm 2</i>
226 neysx 1.11 </pre>
227 drobbins 1.1
228 nightmorph 1.23 <p>
229     As a regular user, you can use <c>java-config --set-user-vm</c>.
230     </p>
231    
232 neysx 1.11 <note>
233 nightmorph 1.23 You no longer have to <c>source</c> the profile for updates to the user/system
234     VM take place.
235 neysx 1.11 </note>
236    
237 nightmorph 1.23 </body>
238     </section>
239     <section id="preferred-vm">
240     <title>Preferred VM</title>
241     <body>
242    
243     <p>
244     While merging Java packages, the VM can and will be switched as necessary.
245     </p>
246    
247     <p>
248     Because of the wide variety of available VMs, we do not have the resources to
249     test and verify every package works on all of them. So to ensure that every
250     packages merges smoothly, we have defined a list of <e>default/supported
251     VMs</e> per arch. You can find them in
252     <path>/usr/share/java-config/config/jdk-defaults.conf</path>. When you are
253     merging a Java package, and it detects one of the VM in that file is installed,
254     it will automatically use that VM, instead of the system-vm.
255     </p>
256    
257 neysx 1.11 <p>
258 nightmorph 1.23 The merge time VM switching is also needed when, for example, your system-vm is
259     set a 1.4 VM and the package you are merging requires a 1.5 VM. While merging
260     it will use the preferred 1.5 VM, leaving your system-vm choice intact.
261 neysx 1.11 </p>
262 drobbins 1.1
263 nightmorph 1.23 <p>
264     Of course, Gentoo is all about choice, so you can override these defaults in
265     <path>/etc/java-config-2/build/jdk.conf</path> and have complete control over
266     which VM will get used. Some examples:
267     </p>
268    
269     <pre caption="Example /etc/java-config-2/build/jdk.conf">
270     <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>
271     *=sun-jdk
272 neysx 1.11 </pre>
273 drobbins 1.1
274 nightmorph 1.23 <pre caption="Example /etc/java-config-2/build/jdk.conf">
275     <comment>(Always use sun-jdk-1.5 wherever possible, except for when a 1.4 or 1.3 VM is explicitly required)</comment>
276     *=sun-jdk-1.5
277     </pre>
278    
279     <pre caption="Example /etc/java-config-2/build/jdk.conf">
280     <comment># For 1.3 I prefer sun-jdk 1.4 but when it is not available, use ibm-jdk-bin,
281     # For 1.4, use blackdown-jdk, and for 1.5, use sun-jdk </comment>
282     1.3=sun-jdk-1.4 ibm-jdk-bin
283     1.4=blackdown-jdk
284     1.5=sun-jdk
285     </pre>
286    
287     <warn>
288     You do not have to edit this file. If you change these options to use a
289     unsupported VM, things could possibly break. Bugs reported with a unsupported
290     VM will a lower priority if they aren't present with supported VMs.
291     </warn>
292    
293     </body>
294     </section>
295     </chapter>
296    
297     <chapter>
298     <title>Compilers</title>
299     <section>
300     <body>
301    
302 neysx 1.11 <p>
303 nightmorph 1.23 The standard Java compiler used for building is javac, which comes with each
304     JDK. In addition to configuring the VM used at build time, it is also possible
305     configure which compiler is used. Essentially, you define a list your
306     preference for which compiler to use in
307     <path>/etc/java-config-2/build/compilers.conf</path>.
308 neysx 1.11 </p>
309    
310 nightmorph 1.23 <pre caption="/etc/java-config-2/build/compilers.conf">
311     # If the ebuild supports it
312     # it will check the COMPILERS var front to back and
313     # use the first compiler that is installed
314    
315     COMPILERS="ecj-3.1 jikes javac"
316     </pre>
317    
318 neysx 1.11 <p>
319 nightmorph 1.23 Some compilers don't support all possible -target and -source arguments.
320     Therefore, each compiler in the list is checked to see if it can support the
321     desired -source/-target. javac will work in all cases, so if no other suitable
322     compiler is found, it will be used instead.
323 neysx 1.11 </p>
324    
325 nightmorph 1.23 <p>
326     More details about each compiler are provided below:
327     </p>
328    
329     <table>
330     <tr>
331     <th>Name</th>
332     <th>Handle</th>
333     <th>Package</th>
334     <th>Description</th>
335     </tr>
336     <tr>
337     <ti>javac</ti>
338     <ti>javac</ti>
339     <ti>N/A</ti>
340     <ti>
341     This is the default compiler that will be used, and comes with each JDK.
342     </ti>
343     </tr>
344     <tr>
345     <ti>jikes</ti>
346     <ti>jikes</ti>
347     <ti>dev-java/jikes</ti>
348     <ti>
349     Jikes was originally developed by IBM. Anecdotally, it is generally quicker
350     than javac. Note however, that it is more pedantic, and will fail under a
351     few circumstances where javac has no issue. It also does not support Java
352     1.5 syntax yet.
353     </ti>
354     </tr>
355     <tr>
356     <ti>Eclipse Compiler for Java</ti>
357     <ti>ecj-3.1</ti>
358     <ti>=dev-java/eclipse-ecj-3.1*</ti>
359     <ti>
360     ECJ is the compiler used by the Eclipse software development kit. It is
361     very full featured, and is pretty fast. It does support Java 1.5 syntax.
362     </ti>
363     </tr>
364     </table>
365    
366     </body>
367     </section>
368     </chapter>
369    
370     <chapter>
371     <title>Setting a default CLASSPATH</title>
372     <section>
373     <body>
374    
375     <warn>
376     The options explained in this section should be considered deprecated and will
377     be most likely be removed in the future. We strongly recommend against using
378     these, because your Java projects or application should ideally manage their
379     own classpaths. If you choose to specify a default CLASSPATH, some applications
380     may behave unexpectedly, because classes they weren't expecting would be on the
381     classpath.
382     </warn>
383    
384     <p>
385     <c>java-config</c> can also be used to set a system-wide default CLASSPATH, as
386     well a user-specific default CLASSPATH.
387     </p>
388    
389     <p>
390     First, you will want to list available Java libraries installed on your system
391     that might want to be put in your CLASSPATH. Here is an example of output:
392     </p>
393    
394     <pre caption="Listing classes">
395     # <i>java-config --list-available-packages</i>
396     [xerces-2] The next generation of high performance, fully compliant XML parsers in the Apache Xerces family (/usr/share/xerces-2/package.env)
397     [junit] Simple framework to write repeatable tests (/usr/share/junit/package.env)
398     [bsh] BeanShell: A small embeddable Java source interpreter (/usr/share/bsh/package.env)
399     [bcel] The Byte Code Engineering Library: analyze, create, manipulate Java class files (/usr/share/bcel/package.env)
400     [log4j] A low-overhead robust logging package for Java (/usr/share/log4j/package.env)
401     ...
402     </pre>
403    
404     <p>
405     Again, the names in brackets (<e>[]</e>) are the IDs that you have to pass to
406     <c>java-config --set-system-classpath</c>. Here is an example:
407     </p>
408    
409     <pre caption="Setting classpaths">
410     # <i>java-config --set-system-classpath log4j,xerces-2</i>
411     </pre>
412    
413     <note>
414     The current directory (<path>.</path>) will not be part of the system
415     classpath, as that should be added in your system's login profile.
416     </note>
417    
418     <p>
419     You will have to update your environment by relogging in or sourcing
420     <path>/etc/profile</path>.
421     </p>
422    
423     <p>
424     For users, <c>java-config --set-user-classpath</c> will create
425     <path>~/.gentoo/java-env-classpath</path>, which you should then source from
426     your shell's profile.
427     </p>
428    
429     <pre caption="Sourcing user specific classpath">
430     <i>if [[ -f "${HOME}/.gentoo/java-env-classpath" ]]; then
431     source ${HOME}/.gentoo/java-env-classpath
432     fi</i>
433     </pre>
434    
435     <p>
436     If you really want a system wide or user default classpath you can add
437     something like like the following to your shell's profile. But we would advise
438     against it.
439     </p>
440    
441     <pre caption="Setting classpath">
442     # <i>export CLASSPATH="${CLASSPATH}:$(java-config --classpath log4j,xerces-2)"</i>
443     </pre>
444    
445 neysx 1.11 </body>
446     </section>
447 swift 1.13 </chapter>
448    
449     <chapter>
450     <title>USE flags for use with Java</title>
451     <section>
452     <title>Setting USE flags</title>
453     <body>
454    
455     <p>
456 rane 1.17 For more information regarding USE flags, refer to the <uri
457     link="/doc/en/handbook/handbook-x86.xml?part=2&amp;chap=2">USE flags</uri>
458 swift 1.13 chapter from the Gentoo Handbook.
459 neysx 1.11 </p>
460    
461     </body>
462     </section>
463 swift 1.13 <section>
464     <title>The flags</title>
465     <body>
466    
467     <ul>
468 nightmorph 1.23 <li>The <b>java</b> flag adds support for Java in a variety of programs</li>
469     <li>
470     The <b>nsplugin</b> flag adds support for Mozilla-like browsers (including
471     Firefox).You will need this for viewing Java applets in your Mozilla-like
472     browser.
473     </li>
474 rane 1.17 <li>
475 nightmorph 1.23 The <b>doc</b> flag will typically install API documentation, as generated
476     by javadoc.
477     </li>
478     <li>
479     The <b>source</b> flag will install a zip of the package's source code.
480     This is typically used to provide your IDE with the source code for the
481     package.
482 rane 1.17 </li>
483 swift 1.13 </ul>
484    
485     </body>
486     </section>
487 neysx 1.11 </chapter>
488    
489     <chapter>
490     <title>Additional resources</title>
491     <section>
492     <title>Off-line resources</title>
493     <body>
494    
495     <ul>
496 rane 1.17 <li>java-config man page</li>
497     <li><c>java-config --help</c></li>
498 neysx 1.11 </ul>
499    
500     </body>
501     </section>
502     <section>
503     <title>Online resources</title>
504     <body>
505 rane 1.17
506 neysx 1.11 <ul>
507 nightmorph 1.23 <li>
508     The <uri link="http://www.gentoo.org/proj/en/java/">Java Project
509     Page</uri>
510     </li>
511 rane 1.17 <li>
512     The <uri
513 nightmorph 1.23 link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>,
514     <uri
515     link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user</uri>, and
516     <uri
517     link="http://news.gmane.org/gmane.linux.gentoo.devel">gentoo-dev</uri>
518 alin 1.18 mailing list archives
519 rane 1.17 </li>
520 alin 1.18 <li>#gentoo and #gentoo-java on irc.freenode.net</li>
521 rane 1.17 <li>
522     <uri
523     link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's
524     entry for Java</uri>
525     </li>
526 neysx 1.11 </ul>
527    
528     </body>
529     </section>
530     </chapter>
531 neysx 1.12 </guide>

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