Java
From the Wikipedia article:
- 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.
Arch Linux officially supports the open source OpenJDK versions 7, 8, and 9. 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.
Contents
Installation
- Installing a JDK will automatically pull its JRE dependency.
- After installation, the Java environment will need to be recognized by the shell (
$PATH
variable). This can be done by sourcing/etc/profile
from the command line or by logging out/in again of a Desktop Environment.
Two common packages are respectively pulled as dependency, named java-runtime-common (containing common files for Java Runtime Environments) and java-environment-common (containing common files for Java Development Kits). The provided environment file /etc/profile.d/jre.sh
points to a linked location /usr/lib/jvm/default/bin
, set by the archlinux-java
helper script. The links /usr/lib/jvm/default
and /usr/lib/jvm/default-runtime
should always be edited with archlinux-java
. This is used to display and point to a working default Java environment in /usr/lib/jvm/java-${JAVA_MAJOR_VERSION}-${VENDOR_NAME}
or a Java runtime in /usr/lib/jvm/java-${JAVA_MAJOR_VERSION}-${VENDOR_NAME}/jre
.
Most executables of the Java installation are provided by direct links in /usr/bin
, while others are available in $PATH
.
/etc/profile.d/jdk.sh
is not provided any more by any package.The following packages are available:
OpenJDK 7 — The open-source implementation of the seventh edition of Java SE.
- http://openjdk.java.net/projects/jdk7/ || jre7-openjdk-headless jre7-openjdk jdk7-openjdk openjdk7-doc openjdk7-src
IBM J9 7 — IBM's implementation of the seventh edition of JRE.
OpenJDK 8 — The open-source implementation of the eight edition of Java SE.
- http://openjdk.java.net/projects/jdk8/ || jre8-openjdk-headless jre8-openjdk jdk8-openjdk openjdk8-doc openjdk8-src
OpenJFX 8 — The open-source implementation of JavaFX. You do not need to install this package if you are making use of Java SE (the Oracle's implementation of JRE and JDK described below). This package only concerns users of the open source implementation of Java (OpenJDK project).
IBM J9 8 — IBM's implementation of the eighth edition of JRE.
OpenJDK 9 — The open-source implementation of the ninth edition of Java SE.
- http://openjdk.java.net/projects/jdk9/ || jre9-openjdk-headless jre9-openjdk jdk9-openjdk openjdk9-doc openjdk9-src
OpenJ9 — Eclipse's implementation of JRE, contributed by IBM.
Java SE — Oracle's implementation of JRE and JDK.
- http://www.oracle.com/technetwork/java/javase/downloads/index.html || jreAUR jre6AUR jre7AUR jre8AUR jre-develAUR jdkAUR jdk5AUR jdk6AUR jdk7AUR jdk8AUR jdk-develAUR
Parrot VM — a VM with experimental support for Java [1] through two different methods: either as a Java VM bytecode translator, or as a Java compiler targeting the Parrot VM.
bin32-
, e.g. bin32-jreAUR and bin32-jdkAUR. They use java32-runtime-commonAUR, which functions as java-runtime-common by suffixing with 32
, e.g. java32
. The same analogy applies to java32-environment-commonAUR, which is only used by 32-bit JDK packages.Flagging packages as out-of-date
Although the Arch Linux package releases may contain a reference to the proprietary versions the packages are based on, the open-source project has its own versioning scheme:
- jre7-openjdk, jdk7-openjdk, and jre7-openjdk-headless should be flagged as out-of-date based on the IcedTea version (e.g.
2.4.3
), rather than on the Oracle reference version (e.g.u45
in the release7.u45_2.4.3-1
). - icedtea-web should be flagged as out-of-date based on the IcedTea Web version (e.g.
1.4.1
). This is independent of the IcedTea version.
Switching between JVM
The 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
<JAVA_ENV_NAME>
names, use archlinux-java status
.Note that archlinux-java
will not let you set an invalid Java environment. In the previous example, jre8-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 an invalid Java environment link is set, calling the archlinux-java fix
command tries to fix it. 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
Launching an application with the non-default java version
If you want to launch an application with another version of java than the default one (for example if you have both version jre7 and jre8 installed on your system), you can wrap your application in a small bash script to locally change the default PATH of java. For example if the default version is jre7 and you want use jre8:
#!/bin/sh export PATH=/usr/lib/jvm/java-8-openjdk/jre/bin/:$PATH exec /path/to/application "$@"
Package pre-requisites to support archlinux-java
archlinux32-java
for 32-bit Java packages, with the proper inclusion of 32
to the package/executable names, where applicable.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:
- Place all files under
/usr/lib/jvm/java-${JAVA_MAJOR_VERSION}-${VENDOR_NAME}
- Ensure all executables for which java-runtime-common and java-environment-common provide links are available in the corresponding package
- Ship links from
/usr/bin
to executables, only if these links do not already belong to java-runtime-common and java-environment-common - Suffix man pages with
-${VENDOR_NAME}${JAVA_MAJOR_VERSION}
to prevent conflicts (see jre8-openjdk file list where man pages are suffixed with-openjdk8
) - Do not declare any conflicts nor replaces with other JDKs,
java-runtime
,java-runtime-headless
norjava-environment
- Use script
archlinux-java
in install functions to set the Java environment as default if no other valid Java environment is already set (ie: package should not force install as default). See officially supported Java environment package sources for examples
Also please note that:
- Packages that need any Java environment should declare dependency on
java-runtime
,java-runtime-headless
orjava-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
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 or Ratpoison.
$ 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.
The standard Java GUI toolkit has a hard-coded list of "non-reparenting" window managers. If using one that is not on that list, there can be some problems with running some Java applications. One of the most common problems is "gray blobs", when the Java application renders as a plain gray box instead of rendering the GUI. Another one might be menus responding to your click, but closing immediately.
There are several things that may help:
- For jre7-openjdk or jre8-openjdk, append the line
export _JAVA_AWT_WM_NONREPARENTING=1
in/etc/profile.d/jre.sh
. Then, source the file/etc/profile.d/jre.sh
or log out and log back in. - For Oracle's JRE/JDK, use SetWMName. However, its effect may be canceled when also using
XMonad.Hooks.EwmhDesktops
. In this case, appending
>> setWMName "LG3D"
to the LogHook
may help.
See [2] for more information.
System freezes when debugging JavaFX Applications
If your system freezes while debugging a JavaFX Application, you can try to supply the JVM option -Dsun.awt.disablegrab=true
.
See http://bugs.java.com/view_bug.do?bug_id=6714678
Tips and tricks
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: -Dawt.useSystemAAFontSettings=on
, -Dswing.aatext=true
See Java Runtime Environment fonts for more detailed information.
Silence 'Picked up _JAVA_OPTIONS' message on command line
Setting the _JAVA_OPTIONS environment variables makes java (openjdk) write to stderr messages of the form: 'Picked up _JAVA_OPTIONS=...'. To suppress those messages in your terminal you can unset the environment variable in your shell startup files and alias java to pass those same options as command line arguments:
_SILENT_JAVA_OPTIONS="$_JAVA_OPTIONS" unset _JAVA_OPTIONS alias java='java "$_SILENT_JAVA_OPTIONS"'
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 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
.
Better 2D performance
Switching to OpenGL-based hardware acceleration pipeline will improve 2D performance
export _JAVA_OPTIONS='-Dsun.java2d.opengl=true'
Non-reparenting window managers / Grey window / Programs not drawing properly
Non-reparenting window managers user should set the following environment variable in their .xinitrc
export _JAVA_AWT_WM_NONREPARENTING=1
Not setting this may result in java programs not being drawn properly.