Java Installation Help

From Gentoo Linux Wiki

[edit] Removing a Sun JRE/JDK installed using the Sun .bin installer

Installing a JRE/JDK using the Sun installer will cause problems. It's heavily recommended that you use portage to install a JRE/JDK. In case you weren't aware of this, here are instructions for removing everything the installer installed.

We are going the use a wonderful script called cruft to remove anything not installed by ebuilds. Cruft will not only remove the JRE/JDK you installed but will also clean other useless files. To use cruft follow the article here in the wiki: using cruft. If you don't want to remove anything else than the JRE/JDK, you have two options 1)just remove the other lines from the cruft.out file, and 2)grep the java lines to remove as follows:

 # grep java cruft.out | xargs rm -rf

After you have removed the JRE/JDK you are ready to install using emerge.

[edit] Installing a JRE/JDK

Just follow the official java guide at gentoo.org:

Gentoo Java Guide

[edit] Java 1.5

Running gentoo with Java 1.5 requires that Java 1.4.2 be installed as well - see Java FAQ for details.

The J2SE 5.0 compiler by default is not compatibile with pre 1.5 source, to maintain backwards compatibility the -source and -target flags are available. Many build scripts for java packages in portage do not take the -source and -target flags into consideration (as of September, 2008); until the issues are resolved dev-java/sun-jdk-1.5.* is masked.

Since gentoo allows multiple Java implementations on a system via java-config 1.4 and 1.5 can coexist.

unmask:

# echo "dev-java/sun-jdk ~x86" >> /etc/portage/package.keywords
# echo "dev-java/java-sdk-docs ~x86" >> /etc/portage/package.keywords
# echo "dev-java/sun-jdk" >> /etc/portage/package.unmask
# echo "dev-java/java-sdk-docs" >> /etc/portage/package.unmask
# echo "dev-java/java-config ~x86" >> /etc/portage/package.keywords
# echo "dev-java/java-config-wrapper ~x86" >> /etc/portage/package.keywords

If the above does not work, simply create a file /etc/portage/package.keywords, and place "dev-java/sun-jdk ~x86" in it. Same thing for the second line.

emerge:

# emerge sun-jdk

view installed java kit:

[sun-jdk-1.5.0.01] "Sun JDK 1.5.0.01" (/etc/env.d/java/20sun-jdk-1.5.0.01) *
[sun-jdk-1.4.2.07] "Sun JDK 1.4.2.07" (/etc/env.d/java/20sun-jdk-1.4.2.07)

suppose you emerge a java-based package and it fails (usually because of the new enum keyword) we can switch back to Java 1.4 temporarily:

System Virtual Machine set
You may want to update your enviroment by running:
        "/usr/sbin/env-update && source /etc/profile"

# /usr/sbin/env-update && source /etc/profile

Re-emerge the package and it should compile properly. Afterwards set the system Java back to 1.5.

• This doesn't seem to work for every package, I had problems compiling dev-java/commons-net-1.2.2-r1 with java 1.5.0 due to enum keywords, switched to 1.4.2.07 and had code version conflicts, I solved the problem by editing the ant build file (build.xml) -> adding source="1.4" to every javac call gives many deprecated and enum-keyword warnings but works: -fhofmann

• Using Java packages compiled with 1.4 and 1.5 on the same system is destined to give problems. Many libraries include ant-tasks. These tasks cannot be loaded when compiled with 1.5, while ant is using 1.4. Therefore I recommend to always use 1.4 when emerging packages. It is safe however to use 1.5 for applications. -Emond Papegaaij

ebuild <ebuild of java build> fetch unpack
vim <path to build.xml>
< add source="1.4" to every javac call >
ebuild compile install qmerge

[edit] References

Gentoo Linux Documentation - Mixing Software Branches -- Explains how to unmask packages.