How do I set the default Java (JDK) version on Mac OS X?

In this post you will learn how to set the default JAVA_HOME in OS X when you have more than one JDK installed in your computer. First you need to run /usr/libexec/java_home -V command to get the list of installed JDK. The command will print out something like the following depending on the available JDK in your computer.

On my machine I have the following version of Java.

Matching Java Virtual Machines (3):
    9, x86_64:  "Java SE 9"     /Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home
    1.8.0_121, x86_64:  "Java SE 8"     /Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home
    1.7.0_80, x86_64:   "Java SE 7"     /Library/Java/JavaVirtualMachines/jdk1.7.0_80.jdk/Contents/Home

From the list above pick which version you want to be the default JDK. For example I will choose the 1.8.0_121 version to be my default JDK. To set it run the command below.

export JAVA_HOME=`/usr/libexec/java_home -v 1.8.0_121`

If the major version of the available JDK is unique you can just use the major version, like:

export JAVA_HOME=`/usr/libexec/java_home -v 1.8`

After setting the JAVA_HOME and you run the java -version command you will see that JDK 1.8 is the new default JDK in your computer.

java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

The change above will only active in the current running shell. If you close or terminate the shell, next time you open the shell you will need to set it again. To make this change permanent you need to set it in your shell init file. For example if you are using bash then you can set the command in the .bash_profile. Add the following lines at the end of the file.

# Setting default JDK to version 1.8.
export JAVA_HOME=`/usr/libexec/java_home -v 1.8`

To activate this configuration right away your can run source .bash_profile. This command reads and executes the .bash_profile in the current shell.

How do I pass password to sudo commands?

If you want to run a sudo command without being prompted to input the password you can do the following command.

echo password | sudo -S rm -rf /opt/jetty/

In the command above we are trying to remove the /opt/jetty directory using the rm -rf command. The -S (stdin) option allow the sudo command to read password from a standard input instead of a terminal device.

If you want to store the password in a file you can use the cat command instead of echo like the following example.

cat password.txt | sudo -S rm -rf /opt/jetty/

How do I install third-party libraries in Maven repository?

Sometimes when the required libraries / dependencies is not available in the Maven Central Repository we need to manually install it to our local repository. This library must be placed in the correct directory in our local repository to enable Maven to find it. The default location is under the ${user.home}/.m2/repository.

To make this job easier Maven provide a maven-install-plugin that will help us to install the third-party library in the correct place. The following command shows how to do it.

The long command

mvn install:install-file -Dfile=<path-to-file> -DgroupId=<group-id> \
        -DartifactId=<artifact-id> -Dversion=<version> -Dpackaging=<packaging>

Where:

  • -Dfile = path to the third-party library file
  • -DgroupId = the groupId of the library
  • -DartifactId = the artifactId of the library
  • -Dversion = the version number of the library
  • -Dpackaging = the library packaging

An example to install an Oracle JDBC library to your local repository is:

mvn install:install-file -Dfile=ojdbc7.jar -DgroupId=com.oracle \
        -DartifactId=ojdbc7 -Dversion=12.1.0.2 -Dpackaging=jar

The simple command

If you have the pom.xml file, you can install it with the following command:

mvn install:install-file \
        -Dfile=<path-to-file> \
        -DpomFile=<path-to-pomfile>

Where:

  • -Dfile = path to the third-party library file
  • -DpomFile = the location to the library pom.xml file

Starting with the Maven version 2.5 you can use even a simpler command. When the library is build by Maven, a pom.xml file will be placed under the META-INF directory. This pom.xml file will be used by default when we install the library. To install a library all you need is the following command:

mvn install:install-file -Dfile=<path-to-file>