Java

From ArchWiki
Revision as of 17:08, 14 October 2014 by Bobpaul (talk | contribs) (Fixed typo in reference to example)
Jump to navigation Jump to search

Related articles

"Java is a programming language originally developed by Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of computer architecture." — Wikipedia article

Arch Linux officially supports the open source OpenJDK versions 7 and 8. All these JVM can be installed without conflict and switched between using helper script archlinux-java. Several other Java environments are available in AUR but are not officially supported.

Installation

The following packages are available in the official repositories:

OpenJDK 7:

Package name Use
jre7-openjdk-headless Java runtime environment (JRE) without any graphical tool - version 7
jre7-openjdk Complete Java Runtime Environment (JRE) - version 7
jdk7-openjdk Java Development Kit (JDK) - version 7
openjdk7-doc OpenJDK javadoc - version 7
openjdk7-src OpenJDK sources - version 7

OpenJDK 8:

Package name Use
jre8-openjdk-headless Java runtime environment (JRE) without any graphical tool - version 8
jre8-openjdk Complete Java Runtime Environment (JRE) - version 8
jdk8-openjdk Java Development Kit (JDK) - version 8
openjdk8-doc OpenJDK javadoc - version 8
openjdk8-src OpenJDK sources - version 8
Note: Installing a JDK will automatically pull its JRE dependency.
Note: After installation, the Java environment will need to be recognized by the shell ($PATH variable). This can be done by sourcing /etc/profile from the command line or by logging out/in again of a Desktop Environment.

Two common packages named java-runtime-common and java-environment-common are automatically pulled as dependency and provide environment file /etc/profile.d/jre.sh. This file contains all JVM common environment variables. Package java-runtime-common also provides a utility script archlinux-java that can display and change the default Java environment. This script sets links /usr/lib/jvm/default and /usr/lib/jvm/default-runtime to point at a valid non-conflicting Java environment installed and Java runtime in /var/lib/jvm/java-${JAVA_MAJOR_VERSION}-${VENDOR_NAME}. Most executable provided by the Java environment set have direct links from /usr/bin, others are available in $PATH.

Warning: File /etc/profile.d/jdk.sh is not provided anymore by any package.

Flagging packages as out-of-date

Although the Arch Linux package releases may contain a reference to the proprietary versions the packages base on, the open-source project has its own versioning:

Switching between JVM

Helper script archlinux-java provides such functionalities: 

archlinux-java <COMMAND>

COMMAND:
	status		List installed Java environments and enabled one
	get		Return the short name of the Java environment set as default
	set <JAVA_ENV>	Force <JAVA_ENV> as default
	unset		Unset current default Java environment
	fix		Fix an invalid/broken default Java environment configuration

List compatible Java environments installed

% archlinux-java status

Example: 

% archlinux-java status
Available Java environments:
  java-7-openjdk (default)
  java-8-openjdk/jre

Note the (default) denoting that java-7-openjdk is currently set as default. Invocation of java and other binaries will rely on this Java install. Also note on the previous output that only the JRE part of OpenJDK 8 is installed here.

Change default Java environment

# archlinux-java set <JAVA_ENV_NAME>

Example: 

# archlinux-java set java-8-openjdk/jre

Note that archlinux-java will not let you set an invalid Java environment. In the previous example, jre7-openjdk is installed but jdk8-openjdk is not so trying to set java-8-openjdk will fail: 

# archlinux-java set java-8-openjdk
'/usr/lib/jvm/java-8-openjdk' is not a valid Java environment path

Unsetting the default Java environment

There should be no need to unset a Java environment as packages providing them should take care of this. Still should you want to do so, just use command unset: 

# archlinux-java unset

Fixing the default Java environment

If /usr/bin links are incorrect or if an invalid Java environment link is set, calling the archlinux-java fix command tries to fix these. Also note that if no default Java environment is set, this will look for valid ones and try to set it for you. Officially supported packages "OpenJDK 7" and "OpenJDK 8" will be considered first in this order, then un-official packages from AUR. 

# archlinux-java fix

Former "One time setup" trick

Formerly, package java-common could be forced into using a Java installation by setting environment variable JAVA_HOME. This cannot be done anymore with latest version of java-runtime-common.

Package pre-requisites to support archlinux-java

This section is targeted at packager willing to provide packages in AUR for an alternate JVM and be able to integrate with Arch Linux JVM scheme to use archlinux-java. To do so, packages should:

Also please note that:

  • Packages that need any Java environment should declare dependency on java-runtime, java-runtime-headless or java-environment as usual
  • Packages that need a specific Java vendor should declare dependency on the corresponding package
  • OpenJDK packages now declare provides="java-runtime-openjdk=${pkgver}" etc. This enables a third-party package to declare dependency on an OpenJDK without specifying a version

Unsupported JVM from AUR

Warning: Packages in AUR may or may not support archlinux-java

Java SE

Several packages from AUR provide Oracle's implementations of JRE and JDK, but the main ones are jreAUR and jdkAUR.

Java SE 6/7

Older versions include jre6AUR/jre6-compatAUR/jre7AUR/jre7-oracleAUR and jdk6AUR/jdk6-compatAUR/jdk7AUR/jdk7-oracleAUR.

Oracle JRockit

JRockit is Oracle's JIT version of Java, available as jrockitAUR.

VMkit

VMkit is an LLVM-based framework for JIT virtual machines. J3 is a JVM running on VMkit. The webpage can be found here: vmkit. J3 depends on the GNU classpath libraries, but may also work with the Apache class path libraries.

Parrot VM

Parrot is a VM that offers experimental support for Java through two different methods: Either as a Java VM bytecode translator or as a Java compiler targeting the Parrot VM. parrot is available in the official repositories and parrot-gitAUR in the AUR.

Troubleshooting

MySQL

Due to the fact that the JDBC-drivers often use the port in the URL to establish a connection to the database, it is considered "remote" (i.e., MySQL does not listen to the port as per its default settings) despite the fact that they are possibly running on the same host, Thus, to use JDBC and MySQL you should enable remote access to MySQL, following the instructions in MySQL#Grant Remote Access.

Impersonate another window manager

You may use the wmname from suckless.org to make the JVM believe you are running a different window manager. This may solve a rendering issue of Java GUIs occurring in window managers like Awesome or Dwm. 

$ wmname LG3D

You must restart the application in question after issuing the wmname command.

This works because the JVM contains a hard-coded list of known, non-re-parenting window managers. For maximum irony, some users prefer to impersonate LG3D, the non-re-parenting window manager written by Sun, in Java.

Illegible fonts

In addition to the suggestions mentioned below in #Better font rendering, some fonts may still not be legible afterwards. If this is the case, there is a good chance Microsoft fonts are being used. Install ttf-ms-fontsAUR from the AUR.

Missing text in some applications

If some applications are completely missing texts it may help to use the options under #Tips and tricks as suggested in FS#40871.

Too many levels of symbolic links

If you get an error like: 

/usr/bin/java: line 2: /usr/lib/jvm/default/bin/java: Too many levels of symbolic links
/usr/bin/java: line 2: exec: /usr/lib/jvm/default/bin/java: cannot execute: Too many levels of symbolic links

#Fixing the default Java environment should solve the problem. See also [1].

Tips and tricks

Note: Suggestions in this section are applicable to all applications, using explicitly installed (external) Java runtime. Some applications are bundled with own (private) runtime or use own mechanics for GUI, font rendering, etc., so none of written below is guaranteed to work.

Behavior of most Java applications can be controlled by supplying predefined variables to Java runtime. From this forum post, a way to do it consists of adding the following line in your ~/.bashrc (or /etc/profile.d/jre.sh to affect programs that are not run by sourcing ~/.bashrc, e.g., launching a program from Gnome's Applications view): 

export _JAVA_OPTIONS="-D<option 1> -D<option 2>..."

For example, to use system anti-aliased fonts and make swing use the GTK look and feel: 

export _JAVA_OPTIONS='-Dawt.useSystemAAFontSettings=on -Dswing.aatext=true -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel'

Better font rendering

Both closed source and open source implementations of Java are known to have improperly implemented anti-aliasing of fonts. This can be fixed with the following options: awt.useSystemAAFontSettings=on, swing.aatext=true

See Java Runtime Environment Fonts for more detailed information.

GTK LookAndFeel

If your Java programs look ugly, you may want to set up the default look and feel for the swing components: swing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel.

Some stubborn Java programs insist on using the cross platform Metal look and feel. In some of these cases you can force these apps to use the GTK look and feel by setting the following property:

swing.crossplatformlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel.

Retrieved from "https://wiki.archlinux.org/index.php?title=Java&oldid=339985"