JDK setup

“Java” is one of the most popular and common language in this world.

It's everywhere, and you need some library to execute these programs.

Get Java

2 versions of Java are available:

• JRE as Java Runtime Environment. For end-users. Download JRE: https://java.com/getjava‎
• JDK as Java Devolpment Kit. For developers and application servers.

The JDK includes the corresponding JRE. Download JDK: http://www.oracle.com/technetwork/java/javase/downloads/index.html

You need to install the JDK on your development station & servers.

Windows installation

1. Create a new environment variable

• Name: JAVA_HOME
• Value: path to your JDK installation (C:\Program Files\java\jdk1.7.0_45)

2. Update the PATH

• Add following sequence to the end of the PATH variable:

      > %JAVA_HOME%\bin

3. Check installation

• Open a new terminal console [Run -> "cmd"]
• Run: java -version

Linux installation

On a server, I advise you to put the JDK instead of the JRE. Many services requires the JDK such as JMX.

While on Windows ORACLE java is almost the only JVM available, on Linux you can choose your JVM vendor: OpenJDK, ORACLE, .... I advise you to use the official ORACLE library, instead of the OpenSource OpenJDK due to stability issues and JavaFX2 compability.

ORACLE JVM automatic installation (ubuntu)

This is for Ubuntu based distributions only.

Add a new repository (automatic):

add-apt-repository ppa:webupd8team/java

Add a new repository (manual):

vim /etc/apt/sources.list

## Java repository
deb http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main



### Install repo key
apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys EEA14886

Install ORACLE JDK packages:

apt-get update
# Oracle JDK 8 - most of the production applications
apt-get install oracle-java8-installer

# OpenJDK 11 - new applications are being develop with it
# /!\ Careful: the ORACLE version is not free, you must pay to use it.
apt install openjdk-11-jdk
apt install openjdk-11-jre

This will download the latest JDK, install it automatically and set the new JVM as the default one.

To remove the repository:

apt-add-repository --remove ppa:webup8team/java

Choose default JVM engine

Register new JVM

To register a new JVM you need to know the path to it:

update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_45/bin/java 1065
update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_45/bin/javac 1065
update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.7.0_45/bin/jar 1065
update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.7.0_45/bin/javaws 1065

Choose default JVM

update-alternatives --config java
update-alternatives --config javac
update-alternatives --config javaws
update-alternatives --config jar

• Check result

java -version

Environment variable JAVA_HOME

You need to add an environment variable JAVA_HOME, if it does not already exist:

• Debian

vim /etc/profile

• Ubuntu

vim /etc/environment

OpenJdk

It’s always good to setup OpenJDK as well, especially for the old versions as there is more updates than the ORACLE version.

apt-get install openjdk-6-jdk openjdk-7-jdk

Choose default java version

update-alternatives --config java
update-alternatives --config javac
update-alternatives --config javaws
update-alternatives --config jar

Reminders

Don't forget to adjust the JAVA_HOME in all JAVA related services:

• Tomcat: /etc/default/tomcat7
• Eclipse IDE: eclipse.ini
• Jenkins
• etc.