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<?xml version="1.0" encoding="UTF-8"?> |
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<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/java.xml,v 1.28 2006/08/08 09:51:12 rane Exp $ --> |
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<!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> |
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|
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<guide link="/doc/en/java.xml"> |
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<title>Gentoo Java Guide</title> |
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|
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<author title="Author"> |
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<mail link="nichoj@gentoo.org">Joshua Nichols</mail> |
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</author> |
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<author title="Author"> |
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<mail link="karltk@gentoo.org">Karl Trygve Kalleberg</mail> |
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</author> |
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<author title="Editor"> |
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<mail link="nightmorph@gentoo.org">Joshua Saddler</mail> |
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</author> |
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|
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<abstract> |
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This guide will introduce you to Java and explain how to use Java with Gentoo |
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Linux. |
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</abstract> |
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|
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<!-- The content of this document is licensed under the CC-BY-SA license --> |
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<!-- See http://creativecommons.org/licenses/by-sa/2.5 --> |
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<license/> |
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|
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<version>0.7</version> |
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<date>2006-08-08</date> |
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|
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<chapter> |
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<title>What is Java?</title> |
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<section> |
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<title>Overview</title> |
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<body> |
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|
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<p> |
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Java is a programming language developed by engineers of Sun Microsystems. The |
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language is object-oriented and designed to run on multiple platforms without |
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the need of recompiling code for each platform. Although Java can be compiled |
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as a native program, much of Java's popularity can be attributed to its |
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portability, along with other features such as garbage collection. To make |
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platform independence possible the Java compiler compiles the Java code to an |
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intermediate representation called "Java bytecode" that runs on a JRE (Java |
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Runtime Environment) and not directly on the operating system. |
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</p> |
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|
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<p> |
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In order to run Java bytecode, one needs to have a JRE (Java Runtime |
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Environment) installed. A JRE provides core libraries, a platform dependent |
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Java Virtual Machine, plug-ins for browsers, among other things. A JDK (Java |
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Development Kit) adds programming tools, such as a bytecode compiler and a |
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debugger. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>New Java System</title> |
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<section> |
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<body> |
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|
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<p> |
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The way Java is handled on Gentoo has recently seen many changes and |
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improvements. This has only happened very recently, and as a result, all the |
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packages related to it are marked with testing keywords, ie ~x86. This |
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document assumes you are using the new system. |
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</p> |
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|
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</body> |
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</section> |
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<section> |
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<title>Keywords</title> |
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<body> |
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|
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<p> |
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If you are using the stable tree, i.e. x86, ppc, or amd64 as opposed to ~x86, |
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~ppc, or ~amd64, you will need to add some entries to your |
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<path>/etc/portage/package.keywords</path>: |
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</p> |
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|
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<pre caption="package.keywords"> |
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# Core Gentoo/Java Packages |
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dev-java/ant-core |
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dev-java/ant-tasks |
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dev-java/ant |
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dev-java/java-config |
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dev-java/java-config-wrapper |
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dev-java/javatoolkit |
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dev-java/sun-jce-bin |
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# JDKs |
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=dev-java/sun-jdk-1.4* |
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=dev-java/sun-jdk-1.5* |
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=dev-java/ibm-jdk-bin-1.4* |
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=dev-java/ibm-jdk-bin-1.5* |
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=dev-java/jrockit-jdk-bin-1.4* |
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=dev-java/jrockit-jdk-bin-1.5* |
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=dev-java/blackdown-jdk-1.4* |
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dev-java/kaffe |
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# JREs |
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=dev-java/sun-jre-bin-1.4* |
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=dev-java/sun-jre-bin-1.5* |
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=dev-java/ibm-jre-bin-1.4* |
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=dev-java/blackdown-jre-1.4* |
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# Virtuals |
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virtual/jdk |
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virtual/jre |
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# Compilers |
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dev-java/eclipse-ecj |
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dev-java/jikes |
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# Documentation |
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dev-java/java-sdk-docs |
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# Misc packages that have been updated to generation-2, |
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# where the generation-1 won't build and/or run properly |
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dev-java/lucene |
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# These have optional Java support, but need ~arch to function properly |
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# with generation-2 |
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dev-util/subversion |
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sys-libs/db |
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</pre> |
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|
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<impo> |
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It is crucial that you keyword ALL packages related to the new Java system, |
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otherwise you will have problems in the later steps of this guide. |
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</impo> |
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|
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<impo> |
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It can't be emphasized enough that you have to have ALL the packages related |
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to the new Java system keyworded for it to function properly. |
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</impo> |
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|
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</body> |
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</section> |
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<section> |
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<title>Existing installs</title> |
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<body> |
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|
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<p> |
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For existing installs, regardless of if you have installed anything Java |
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before, make sure you have followed the <uri |
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link="/proj/en/java/java-upgrade.xml">Java Upgrade Guide</uri>. |
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</p> |
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|
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</body> |
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</section> |
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<section> |
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<title>New installs</title> |
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<body> |
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|
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<p> |
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New installs should require no further preparation. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Installing a Virtual Machine</title> |
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<section> |
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<title>The choices</title> |
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<body> |
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|
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<p> |
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Gentoo provides numerous Runtime Environments (JREs) and Development Kits |
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(JDKs). Among the current choices, we have: |
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</p> |
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|
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<table> |
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<tr> |
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<th>Vendor</th> |
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<th>JDK</th> |
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<th>JRE</th> |
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</tr> |
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<tr> |
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<ti>The Blackdown Java Kit</ti> |
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<ti>dev-java/blackdown-jdk</ti> |
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<ti>dev-java/blackdown-jre</ti> |
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</tr> |
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<tr> |
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<ti>Sun's Java Kit</ti> |
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<ti>dev-java/sun-jdk</ti> |
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<ti>dev-java/sun-jre-bin</ti> |
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</tr> |
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<tr> |
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<ti>The IBM Java Kit</ti> |
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<ti>dev-java/ibm-jdk-bin</ti> |
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<ti>dev-java/ibm-jre-bin</ti> |
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</tr> |
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<tr> |
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<ti>The Compaq Java Kit for Alpha/Linux/GNU</ti> |
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<ti>dev-java/compaq-jdk</ti> |
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<ti>dev-java/compaq-jre</ti> |
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</tr> |
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<tr> |
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<ti>BEA WebLogic's J2SE Development Kit</ti> |
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<ti>dev-java/jrockit-jdk-bin</ti> |
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</tr> |
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</table> |
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|
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<!-- |
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TODO: list free implementations? |
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note about not drop-in replacements |
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kaffe/sablevm/gcj/jamvm |
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--> |
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|
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<p> |
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The default is Blackdown for both the JRE and the JDK, as it is freely ("free |
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as in beer") available without any registration fuss. |
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</p> |
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|
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<p> |
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The default for Java 1.4 is the Blackdown JRE/JDK pair, as it is freely |
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("free as in beer") available without any registration fuss. |
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</p> |
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|
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<p> |
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JREs and JDKs from Sun, IBM, and BEA are generally faster, but getting them |
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is a bit more work, as you are required to read and accept their license before |
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downloading (IBM additionally requires you to register). |
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</p> |
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|
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</body> |
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</section> |
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<section> |
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<title>Installing a JRE/JDKs</title> |
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<body> |
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|
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<p> |
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To install your profile's default JDK, you can run <c>emerge virtual/jdk</c>. |
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Or to install your profile's default JRE, you can <c>emerge virtual/jre</c>. |
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</p> |
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|
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<p> |
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In recent events, Sun has relicensed their JDK and JRE under a more Linux |
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distro friendly license. As a result, Sun releases Java 1.5 and onwards are |
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freely downloadable, without any further hassle. |
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</p> |
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|
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<note> |
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A JDK also includes a JRE, so if you install a JDK you shouldn't have to also |
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have to install a JRE. |
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</note> |
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|
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</body> |
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</section> |
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<section> |
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<title>Installing fetch-restricted virtual machines</title> |
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<body> |
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|
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<p> |
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As already mentioned, some of the JDKs and JREs require you to jump through a |
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few hoops before installing. Simply emerge the packages as you normally would. |
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The ebuilds will then instruct you where to go and what to download. |
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</p> |
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|
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<p> |
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You should download the indicated file(s) into |
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<path>/usr/portage/distfiles</path>. Once there, you can rerun the emerge |
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command, at which point the JRE/JDK will be begin to install. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Configuring your virtual machine</title> |
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<section> |
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<title>Overview</title> |
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<body> |
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|
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<p> |
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Gentoo has the ability to have multiple JDKs and JREs installed without causing |
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conflicts. |
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</p> |
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|
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<p> |
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Using the <c>java-config</c> tool, you can set the system-wide default |
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(provided you have root access). Users can also use <c>java-config</c> to set |
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up their own personal default. |
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</p> |
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|
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<note> |
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You can also use <e>eselect</e> to change the system and user vm. See |
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<c>eselect java-vm help</c>. |
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</note> |
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|
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</body> |
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</section> |
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<section> |
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<title>Setting a default virtual machine</title> |
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<body> |
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|
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<p> |
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Running the command <c>java-config --list-available-vms</c> will give you a |
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list of all JREs and JDKs installed on your system. Here is an example of |
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output: |
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</p> |
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|
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<pre caption="Listing available VMs"> |
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# <i>java-config --list-available-vms</i> |
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1) Blackdown JDK 1.3.1 [blackdown-jdk-1.3] (/etc/env.d/java/20blackdown-jdk-1.3) |
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2) Blackdown JDK 1.4.2.02 [blackdown-jdk-1.4] (/etc/env.d/java/20blackdown-jdk-1.4) |
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3) Blackdown JRE 1.4.2.02 [blackdown-jre-1.4] (/etc/env.d/java/20blackdown-jre-1.4) |
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4) IBM JDK 1.4.2 [ibm-jdk-bin-1.4] (/etc/env.d/java/20ibm-jdk-bin-1.4) |
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5) IBM JRE 1.4.2 [ibm-jre-bin-1.4] (/etc/env.d/java/20ibm-jre-bin-1.4) |
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6) WebLogic JRockit 1.4.2.05 [jrockit-jdk-bin-1.4] (/etc/env.d/java/20jrockit-jdk-bin-1.4) |
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7) WebLogic JRockit 1.5.0.03 [jrockit-jdk-bin-1.5] (/etc/env.d/java/20jrockit-jdk-bin-1.5) |
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8) Sun JDK 1.3.1.13 [sun-jdk-1.3] (/etc/env.d/java/20sun-jdk-1.3) |
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9) Sun JDK 1.4.2.09 [sun-jdk-1.4] (/etc/env.d/java/20sun-jdk-1.4) |
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*) Sun JDK 1.5.0.04 [sun-jdk-1.5] (/etc/env.d/java/20sun-jdk-1.5) |
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11) Sun JRE 1.4.2.09 [sun-jre-bin-1.4] (/etc/env.d/java/20sun-jre-bin-1.4) |
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12) Sun JRE 1.5.0.04 [sun-jre-bin-1.5] (/etc/env.d/java/20sun-jre-bin-1.5) |
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</pre> |
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|
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<p> |
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The <e>*</e> indicates this is the current active vm (system-vm or user-vm when |
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set). The name in the brackets (<e>[]</e>) is the handle or ID for that |
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particular VM. You use the handle or the number to <c>java-config |
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--set-system-vm</c>. Here is an example of how to set the system VM. |
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</p> |
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|
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<pre caption="Setting the System VM"> |
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<comment>(By handle (preferred))</comment> |
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# <i>java-config --set-system-vm blackdown-jdk-1.4</i> |
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<comment>(By number)</comment> |
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# <i>java-config --set-system-vm 2</i> |
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</pre> |
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|
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<p> |
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As a regular user, you can use <c>java-config --set-user-vm</c>. |
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</p> |
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|
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<note> |
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You no longer have to <c>source</c> the profile for updates to the user/system |
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VM take place. |
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</note> |
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|
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</body> |
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</section> |
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<section id="preferred-vm"> |
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<title>Preferred VM</title> |
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<body> |
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|
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<p> |
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While merging Java packages, the VM can and will be switched as necessary. |
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</p> |
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|
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<p> |
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Because of the wide variety of available VMs, we do not have the resources to |
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test and verify every package works on all of them. So to ensure that every |
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packages merges smoothly, we have defined a list of <e>default/supported |
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VMs</e> per arch. You can find them in |
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<path>/usr/share/java-config/config/jdk-defaults.conf</path>. When you are |
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merging a Java package, and it detects one of the VM in that file is installed, |
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it will automatically use that VM, instead of the system-vm. |
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</p> |
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|
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<p> |
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The merge time VM switching is also needed when, for example, your system-vm is |
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set a 1.4 VM and the package you are merging requires a 1.5 VM. While merging |
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it will use the preferred 1.5 VM, leaving your system-vm choice intact. |
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</p> |
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|
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<p> |
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Of course, Gentoo is all about choice, so you can override these defaults in |
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<path>/etc/java-config-2/build/jdk.conf</path> and have complete control over |
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which VM will get used. Some examples: |
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</p> |
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|
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<pre caption="Example /etc/java-config-2/build/jdk.conf"> |
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<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> |
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*=sun-jdk |
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</pre> |
| 377 |
|
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<pre caption="Example /etc/java-config-2/build/jdk.conf"> |
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<comment>(Always use sun-jdk-1.5 wherever possible, except for when a 1.4 or 1.3 VM is explicitly required)</comment> |
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*=sun-jdk-1.5 |
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</pre> |
| 382 |
|
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<pre caption="Example /etc/java-config-2/build/jdk.conf"> |
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<comment># For 1.3 I prefer sun-jdk 1.4 but when it is not available, use ibm-jdk-bin, |
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# For 1.4, use blackdown-jdk, and for 1.5, use sun-jdk </comment> |
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1.3=sun-jdk-1.4 ibm-jdk-bin |
| 387 |
1.4=blackdown-jdk |
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1.5=sun-jdk |
| 389 |
</pre> |
| 390 |
|
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<warn> |
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You do not have to edit this file. If you change these options to use a |
| 393 |
unsupported VM, things could possibly break. Bugs reported with a unsupported |
| 394 |
VM won't be prioritized as much as bugs present within supported VMs. |
| 395 |
</warn> |
| 396 |
|
| 397 |
</body> |
| 398 |
</section> |
| 399 |
</chapter> |
| 400 |
|
| 401 |
<chapter> |
| 402 |
<title>Compilers</title> |
| 403 |
<section> |
| 404 |
<body> |
| 405 |
|
| 406 |
<p> |
| 407 |
The standard Java compiler used for building is javac, which comes with each |
| 408 |
JDK. In addition to configuring the VM used at build time, it is also possible |
| 409 |
configure which compiler is used. Essentially, you define a list your |
| 410 |
preference for which compiler to use in |
| 411 |
<path>/etc/java-config-2/build/compilers.conf</path>. |
| 412 |
</p> |
| 413 |
|
| 414 |
<pre caption="/etc/java-config-2/build/compilers.conf"> |
| 415 |
# If the ebuild supports it |
| 416 |
# it will check the COMPILERS var front to back and |
| 417 |
# use the first compiler that is installed |
| 418 |
|
| 419 |
COMPILERS="ecj-3.1 jikes javac" |
| 420 |
</pre> |
| 421 |
|
| 422 |
<p> |
| 423 |
Some compilers don't support all possible -target and -source arguments. |
| 424 |
Therefore, each compiler in the list is checked to see if it can support the |
| 425 |
desired -source/-target. javac will work in all cases, so if no other suitable |
| 426 |
compiler is found, it will be used instead. |
| 427 |
</p> |
| 428 |
|
| 429 |
<p> |
| 430 |
More details about each compiler are provided below: |
| 431 |
</p> |
| 432 |
|
| 433 |
<table> |
| 434 |
<tr> |
| 435 |
<th>Name</th> |
| 436 |
<th>Handle</th> |
| 437 |
<th>Package</th> |
| 438 |
<th>Description</th> |
| 439 |
</tr> |
| 440 |
<tr> |
| 441 |
<ti>javac</ti> |
| 442 |
<ti>javac</ti> |
| 443 |
<ti>N/A</ti> |
| 444 |
<ti> |
| 445 |
This is the default compiler that will be used, and comes with each JDK. |
| 446 |
</ti> |
| 447 |
</tr> |
| 448 |
<tr> |
| 449 |
<ti>jikes</ti> |
| 450 |
<ti>jikes</ti> |
| 451 |
<ti>dev-java/jikes</ti> |
| 452 |
<ti> |
| 453 |
Jikes was originally developed by IBM. Anecdotally, it is generally quicker |
| 454 |
than javac. Note however, that it is more pedantic, and will fail under a |
| 455 |
few circumstances where javac has no issue. It also does not support Java |
| 456 |
1.5 syntax yet. |
| 457 |
</ti> |
| 458 |
</tr> |
| 459 |
<tr> |
| 460 |
<ti>Eclipse Compiler for Java</ti> |
| 461 |
<ti>ecj-3.1</ti> |
| 462 |
<ti>=dev-java/eclipse-ecj-3.1*</ti> |
| 463 |
<ti> |
| 464 |
ECJ is the compiler used by the Eclipse software development kit. It is |
| 465 |
very full featured, and is pretty fast. It does support Java 1.5 syntax. |
| 466 |
</ti> |
| 467 |
</tr> |
| 468 |
</table> |
| 469 |
|
| 470 |
</body> |
| 471 |
</section> |
| 472 |
</chapter> |
| 473 |
|
| 474 |
<chapter> |
| 475 |
<title>Setting a default CLASSPATH</title> |
| 476 |
<section> |
| 477 |
<body> |
| 478 |
|
| 479 |
<warn> |
| 480 |
The options explained in this section should be considered deprecated and will |
| 481 |
most likely be removed in the future. We strongly recommend against using |
| 482 |
these, because your Java projects or application should ideally manage their |
| 483 |
own classpaths. If you choose to specify a default CLASSPATH, some applications |
| 484 |
may behave unexpectedly, because classes they weren't expecting would be on the |
| 485 |
classpath. |
| 486 |
</warn> |
| 487 |
|
| 488 |
<p> |
| 489 |
<c>java-config</c> can also be used to set a system-wide default CLASSPATH, as |
| 490 |
well a user-specific default CLASSPATH. |
| 491 |
</p> |
| 492 |
|
| 493 |
<p> |
| 494 |
First, you will want to list available Java libraries installed on your system |
| 495 |
that might want to be put in your CLASSPATH. Here is an example of output: |
| 496 |
</p> |
| 497 |
|
| 498 |
<pre caption="Listing classes"> |
| 499 |
# <i>java-config --list-available-packages</i> |
| 500 |
[xerces-2] The next generation of high performance, fully compliant XML parsers in the Apache Xerces family (/usr/share/xerces-2/package.env) |
| 501 |
[junit] Simple framework to write repeatable tests (/usr/share/junit/package.env) |
| 502 |
[bsh] BeanShell: A small embeddable Java source interpreter (/usr/share/bsh/package.env) |
| 503 |
[bcel] The Byte Code Engineering Library: analyze, create, manipulate Java class files (/usr/share/bcel/package.env) |
| 504 |
[log4j] A low-overhead robust logging package for Java (/usr/share/log4j/package.env) |
| 505 |
... |
| 506 |
</pre> |
| 507 |
|
| 508 |
<p> |
| 509 |
Again, the names in brackets (<e>[]</e>) are the IDs that you have to pass to |
| 510 |
<c>java-config --set-system-classpath</c>. Here is an example: |
| 511 |
</p> |
| 512 |
|
| 513 |
<pre caption="Setting classpaths"> |
| 514 |
# <i>java-config --set-system-classpath log4j,xerces-2</i> |
| 515 |
</pre> |
| 516 |
|
| 517 |
<note> |
| 518 |
The current directory (<path>.</path>) will not be part of the system |
| 519 |
classpath, as that should be added in your system's login profile. |
| 520 |
</note> |
| 521 |
|
| 522 |
<p> |
| 523 |
You will have to update your environment by logging out, then in again or |
| 524 |
sourcing <path>/etc/profile</path>. |
| 525 |
</p> |
| 526 |
|
| 527 |
<p> |
| 528 |
For users, <c>java-config --set-user-classpath</c> will create |
| 529 |
<path>~/.gentoo/java-env-classpath</path>, which you should then source from |
| 530 |
your shell's profile. |
| 531 |
</p> |
| 532 |
|
| 533 |
<pre caption="Sourcing user specific classpath"> |
| 534 |
<i>if [[ -f "${HOME}/.gentoo/java-env-classpath" ]]; then |
| 535 |
source ${HOME}/.gentoo/java-env-classpath |
| 536 |
fi</i> |
| 537 |
</pre> |
| 538 |
|
| 539 |
<p> |
| 540 |
If you really want a system wide or user default classpath you can add |
| 541 |
something like the following to your shell's profile. But we would advise |
| 542 |
against it. |
| 543 |
</p> |
| 544 |
|
| 545 |
<pre caption="Setting classpath"> |
| 546 |
# <i>export CLASSPATH="${CLASSPATH}:$(java-config --classpath log4j,xerces-2)"</i> |
| 547 |
</pre> |
| 548 |
|
| 549 |
</body> |
| 550 |
</section> |
| 551 |
</chapter> |
| 552 |
|
| 553 |
<chapter> |
| 554 |
<title>USE flags for use with Java</title> |
| 555 |
<section> |
| 556 |
<title>Setting USE flags</title> |
| 557 |
<body> |
| 558 |
|
| 559 |
<p> |
| 560 |
For more information regarding USE flags, refer to the <uri |
| 561 |
link="/doc/en/handbook/handbook-x86.xml?part=2&chap=2">USE flags</uri> |
| 562 |
chapter from the Gentoo Handbook. |
| 563 |
</p> |
| 564 |
|
| 565 |
</body> |
| 566 |
</section> |
| 567 |
<section> |
| 568 |
<title>The flags</title> |
| 569 |
<body> |
| 570 |
|
| 571 |
<ul> |
| 572 |
<li>The <b>java</b> flag adds support for Java in a variety of programs</li> |
| 573 |
<li> |
| 574 |
The <b>nsplugin</b> flag adds support for Mozilla-like browsers (including |
| 575 |
Firefox).You will need this for viewing Java applets in your Mozilla-like |
| 576 |
browser. |
| 577 |
</li> |
| 578 |
<li> |
| 579 |
The <b>doc</b> flag will typically install API documentation, as generated |
| 580 |
by javadoc. |
| 581 |
</li> |
| 582 |
<li> |
| 583 |
The <b>source</b> flag will install a zip of the package's source code. |
| 584 |
This is typically used to provide your IDE with the source code for the |
| 585 |
package. |
| 586 |
</li> |
| 587 |
<li> |
| 588 |
The <b>source</b> flag installs a zip of the source code of a package. |
| 589 |
This is traditionally used for for IDEs to 'attach' source to the libraries |
| 590 |
you are using. |
| 591 |
</li> |
| 592 |
<li> |
| 593 |
For Java packages, the <b>doc</b> flag will build API documentation using |
| 594 |
javadoc. |
| 595 |
</li> |
| 596 |
</ul> |
| 597 |
|
| 598 |
</body> |
| 599 |
</section> |
| 600 |
</chapter> |
| 601 |
|
| 602 |
<chapter> |
| 603 |
<title>Additional resources</title> |
| 604 |
<section> |
| 605 |
<title>Off-line resources</title> |
| 606 |
<body> |
| 607 |
|
| 608 |
<ul> |
| 609 |
<li>java-config man page</li> |
| 610 |
<li><c>java-config --help</c></li> |
| 611 |
</ul> |
| 612 |
|
| 613 |
</body> |
| 614 |
</section> |
| 615 |
<section> |
| 616 |
<title>Online resources</title> |
| 617 |
<body> |
| 618 |
|
| 619 |
<ul> |
| 620 |
<li> |
| 621 |
The <uri link="http://www.gentoo.org/proj/en/java/">Java Project |
| 622 |
Page</uri> |
| 623 |
</li> |
| 624 |
<li> |
| 625 |
The <uri |
| 626 |
link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>, |
| 627 |
<uri |
| 628 |
link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user</uri>, and |
| 629 |
<uri |
| 630 |
link="http://news.gmane.org/gmane.linux.gentoo.devel">gentoo-dev</uri> |
| 631 |
mailing list archives |
| 632 |
</li> |
| 633 |
<li>#gentoo and #gentoo-java on irc.freenode.net</li> |
| 634 |
<li> |
| 635 |
<uri |
| 636 |
link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's |
| 637 |
entry for Java</uri> |
| 638 |
</li> |
| 639 |
</ul> |
| 640 |
|
| 641 |
</body> |
| 642 |
</section> |
| 643 |
</chapter> |
| 644 |
</guide> |
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