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1 neysx 1.11 <?xml version="1.0" encoding="UTF-8"?>
2 alin 1.18 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/java.xml,v 1.17 2005/09/29 18:27:31 rane 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     <author title="Author and Editor">
9     <mail link="karltk@gentoo.org">Karl Trygve Kalleberg</mail>
10     </author>
11     <author title="Editor">
12     <mail link="swift@gentoo.org">Sven Vermeulen</mail>
13     </author>
14 swift 1.13 <author title="Editor">
15 swift 1.15 <mail link="vanquirius@gentoo.org">Marcelo Góes</mail>
16 swift 1.13 </author>
17 neysx 1.11
18     <abstract>
19 swift 1.13 This guide will introduce users and developers to Java and explain how to use
20     Java with Gentoo Linux.
21 neysx 1.11 </abstract>
22    
23     <license/>
24    
25 rane 1.16 <version>0.1.7</version>
26     <date>2005-09-29</date>
27 neysx 1.11
28     <chapter>
29 swift 1.13 <title>What is Java?</title>
30 neysx 1.11 <section>
31     <title>Overview</title>
32     <body>
33    
34     <p>
35 swift 1.13 Java is a programming language developed by engineers of Sun Microsystems.
36     The language is object-oriented and designed to run on multiple platforms
37     without the need of recompiling code for each platform. Although Java can
38     be compiled as a native program, much of Java's popularity can be attributed
39     to its portability, along with other features such as garbage collection.
40     The ability to compile once and run in various platforms is achieved through
41     the use of just-in-time compilers (JIT), which compile Java bytecodes into
42     native code when a given program is run.
43     </p>
44    
45     <p>
46     In order to run Java bytecodes, one needs to have a JRE (Java Runtime Environment)
47     installed. A JRE provides core libraries, a platform dependent Java Virtual Machine,
48     plug-ins for browsers, among other things. A JDK (Java Development Kit) adds
49     programming tools, such as a bytecode compiler and a debugger.
50     </p>
51    
52     </body>
53     </section>
54     </chapter>
55    
56     <chapter>
57     <title>Installing a JRE/JDK</title>
58     <section>
59     <title>The choices</title>
60     <body>
61    
62     <p>
63     Gentoo provides numerous JREs and JDKs. Among the current alternatives, we have:
64     </p>
65    
66     <ul>
67 rane 1.17 <li>blackdown-jre and blackdown-jdk, the Blackdown Java Kit</li>
68     <li>sun-jre-bin and sun-jdk, Sun's Java Kit </li>
69     <li>ibm-jre-bin and ibm-jdk-bin, the IBM Java Kit</li>
70     <li>compaq-jre and compaq-jdk, the Compaq Java Kit for Alpha/Linux/GNU</li>
71     <li>jrockit-jdk-bin, BEA WebLogic's J2SE Development Kit</li>
72 swift 1.13 </ul>
73    
74     <p>
75     The default is the Blackdown JRE/JDK
76 swift 1.14 pair, as it is freely ("free as in beer") available without any registration
77     fuss.
78 neysx 1.11 </p>
79    
80     <p>
81 swift 1.13 Both the Sun JRE/JDK and the IBM JRE/JDK are generally faster, but getting them
82 neysx 1.11 is a bit more work, as you are required to read and accept their license before
83     downloading (IBM additionally requires you to register).
84     </p>
85    
86     <p>
87 swift 1.13 Our ebuilds for the Sun and IBM JRE/JDKs will notify you of where to go to
88 neysx 1.11 download them.
89     </p>
90    
91     </body>
92     </section>
93     <section>
94 swift 1.13 <title>Installing the Sun/IBM JRE/JDKs</title>
95 neysx 1.11 <body>
96    
97     <p>
98 swift 1.13 If you run <c>emerge =sun-jdk-1.4.2.06</c> or <c>=ibm-jdk-bin-1.4.2</c>, you will
99 neysx 1.11 be notified that you are required to download the actual tarballs yourself. This
100 swift 1.13 has to do with license restrictions for the Sun JRE/JDK (online click-wrap
101     license) and registration issues with the IBM JRE/JDK.
102 neysx 1.11 </p>
103    
104     <note>
105 swift 1.13 ibm-jdk-bin is currently masked, you may have to unmask it to use it.
106 neysx 1.11 </note>
107    
108     <p>
109     You should download the indicated file(s) into
110     <path>/usr/portage/distfiles</path>. Once that is done, you can rerun the emerge
111 swift 1.13 command, then the JRE/JDK will be installed properly into <path>/opt</path>.
112 neysx 1.11 </p>
113    
114     </body>
115     </section>
116     </chapter>
117    
118     <chapter>
119 swift 1.13 <title>Configuring your JRE/JDK</title>
120 neysx 1.11 <section>
121     <title>Overview</title>
122     <body>
123    
124     <p>
125     Gentoo has the ability to have multiple JDKs and JREs installed without them
126     conflicting.
127     </p>
128    
129     <p>
130     Using the <c>java-config</c> tool, you can set the system-wide default if you
131     have root access. Users can also use <c>java-config</c> to set up their own
132     personal default, that is different from the system-wide default.
133     </p>
134    
135     </body>
136     </section>
137    
138     <section>
139 swift 1.13 <title>Setting a default JRE/JDK</title>
140 neysx 1.11 <body>
141    
142     <p>
143     Running the command <c>java-config --list-available-vms</c> will give you a list
144 swift 1.13 of all available JREs and JDKs on your system. Here is an example of output:
145 neysx 1.11 </p>
146    
147     <pre caption="Listing available VMs">
148 neysx 1.12 # <i>java-config --list-available-vms</i>
149 drobbins 1.1 [blackdown-jdk-1.3.1] Blackdown JDK 1.3.1 (/etc/env.d/java/20blackdown-jdk-1.3.1)
150     [blackdown-jre-1.3.1] Blackdown JRE 1.3.1 (/etc/env.d/java/20blackdown-jre-1.3.1)
151     [ibm-jdk-1.3.0] IBM JDK 1.3.0 (/etc/env.d/java/20ibm-jdk-1.3.0)
152     [ibm-jdk-1.3.1] IBM JDK 1.3.1 (/etc/env.d/java/20ibm-jdk-1.3.1)
153     [ibm-jre-1.3.1] IBM JRE 1.3.1 (/etc/env.d/java/20ibm-jre-1.3.1)
154     [sun-jdk-1.4.0] Sun JDK 1.4.0 (/etc/env.d/java/20sun-jdk-1.4.0)
155 neysx 1.11 </pre>
156    
157     <p>
158     The name in the brackets <path>"[]"</path> is the handle or ID for that
159 swift 1.13 particular VM. You use pass that ID to <c>java-config --set-system-vm</c>. Here is
160     an example of how to set the system VM.
161 neysx 1.11 </p>
162 zhen 1.4
163 neysx 1.11 <pre caption="Setting the System VM">
164 neysx 1.12 # <i>java-config --set-system-vm=ibm-jdk-1.3.1</i>
165 drobbins 1.1 Now using IBM JDK 1.3.1 (/etc/env.d/java/20ibm-jdk-1.3.1)
166 neysx 1.11 </pre>
167 drobbins 1.1
168 neysx 1.11 <note>
169     You will have to be root to run --set-system-vm.
170     </note>
171    
172     <p>
173 rane 1.17 Once you have issued <c>java-config --set-system-vm</c> with a particular VM
174     ID, you will need to regenerate your <path>/etc/profile.env</path>. You can do
175     it like this:
176 neysx 1.11 </p>
177 drobbins 1.1
178 neysx 1.11 <pre caption="Regenerating /etc/profile.env" >
179 neysx 1.12 # <i>env-update</i>
180 neysx 1.11 </pre>
181 drobbins 1.1
182 neysx 1.11 <p>
183     After this, you will either want to relogin, or resource
184     <path>/etc/profile</path> into your environment.
185     </p>
186    
187     <p>
188     As a regular user, you can use <c>java-config --set-user-vm</c>, which will
189 swift 1.13 create <path>~/.gentoo/java-env</path> with all required env vars. You would
190 rane 1.17 normally source this from your shell's startup script (generally
191     <path>~/.bashrc</path>).
192 neysx 1.11 </p>
193    
194     </body>
195     </section>
196 swift 1.13 </chapter>
197    
198     <chapter>
199     <title>USE flags for use with Java</title>
200     <section>
201     <title>Setting USE flags</title>
202     <body>
203    
204     <p>
205 rane 1.17 For more information regarding USE flags, refer to the <uri
206     link="/doc/en/handbook/handbook-x86.xml?part=2&amp;chap=2">USE flags</uri>
207 swift 1.13 chapter from the Gentoo Handbook.
208 neysx 1.11 </p>
209    
210     </body>
211     </section>
212 swift 1.13 <section>
213     <title>The flags</title>
214     <body>
215    
216     <ul>
217 rane 1.17 <li>The <b>java</b> flag adds support for Java in a variety of programs.</li>
218     <li>
219     The <b>browserplugin</b> flag adds support for Mozilla-like browsers
220     (including Firefox) if you are using blackdown's Java kit. You will need
221     this for viewing Java applets in your Mozilla-like browser.
222     </li>
223 swift 1.13 </ul>
224    
225     </body>
226     </section>
227 neysx 1.11 </chapter>
228    
229     <chapter>
230     <title>Additional resources</title>
231     <section>
232     <title>Off-line resources</title>
233     <body>
234    
235     <ul>
236 rane 1.17 <li>java-config man page</li>
237     <li><c>java-config --help</c></li>
238     <li>The <path>/usr/bin/java-config</path> script itself</li>
239 neysx 1.11 </ul>
240    
241     </body>
242     </section>
243     <section>
244     <title>Online resources</title>
245     <body>
246 rane 1.17
247 neysx 1.11 <ul>
248 rane 1.17 <li>
249     The <uri
250     link="http://news.gmane.org/gmane.linux.gentoo.devel">gentoo-dev</uri>,
251     <uri link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user
252     </uri> and <uri
253     link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>
254 alin 1.18 mailing list archives
255 rane 1.17 </li>
256 alin 1.18 <li>#gentoo and #gentoo-java on irc.freenode.net</li>
257 rane 1.17 <li>
258     <uri
259     link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's
260     entry for Java</uri>
261     </li>
262 neysx 1.11 </ul>
263    
264     </body>
265     </section>
266     </chapter>
267 neysx 1.12 </guide>

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