Changing the JAVA JRE for Liberty Profile

This guide explains How to install the IBM SDK or JRE using the public downloads.

It is possible to acquire the IBM SDK from the following URL, though you will need to register before downloading.

• I have chosen to downloaded the 64 Bit version for the IBM 8 SDK/JRE
  

Note: It all depends on your requirements i.e. the application requirements to decide what SDK is required. In this example, I have used the IBM 8 SDK/JRE to demonstrate that Liberty can run in IBM 8 JRE

• I was then prompted to register with IBM before I can continue.
  

• Once I located the actual download page, I selected all the SDK options for example JDK and JRE and samples just in case I need them at another stage.
  

For Liberty we would only actually require the JRE to replace the standard default OpenJDK on CentOS for example.

In this example we will only install the IBM 8 JRE the file is:

To do this we follow these steps:

Copy the JRE download to an appropriate folder for example:

Modify to be able to run the bin file:

• Select the default options
  

Result:

We now have installed IBM 8 JRE into:

To change the JRE current version or use a different vendor i.e. in our case we wish to use IBM’s JRE as opposed to the default CentOS JRE, we can choose one of several options:

• Use JAVA_HOME
  
• Use a server.env file
  

Using JAVA_HOME in .bash_profile

JAVA_HOME will ensure that the current logged in user will use the specified JRE when several applications/products on the same machine refer to JAVA_HOME, this may not be what you want. But if this machine is only for Liberty then this is an easy choice.

Steps:

• First we will verify the current JRE that is set for your environment, so we can test later that it has been changed.
  

Result:

We will now need to set our environment buy editing .bash_profile

We want to set JAVA_HOME to where we have our JDK installed for example:

If JAVA_HOME/bin is not in the PATH, add it to the path:

• Edit your local bash profile (~/.bash_profile) and add two lines:
  

Example .bash_profile

We can either logout and re-login for the changes to take effect or we can source (execute) .bash_profile from our current session:

• Now check what JRE is running for example:
  

Result:

• We can now start an existing Liberty Server for example we have a liberty instance installed in /var/apps/wasnd855_lp/ and we have created a server called server1
  

We can see that JRE used by looking at console.log for example:

Result:

We can now see that Liberty is now using the IBM JRE as opposed to the default CentoOS OpenJDK, but the issue is that now IBM JRE will be used for all application/software that refer to Java_HOME, and we may not want this. We may wish to have only Liberty use the IBM JRE. To do this we must refer to a server.env file.

Specifying JAVA_HOME using server.env

Before we do this, we will remove the edits made to .bash_profile to ensure that JAVA_HOME is not set as an environment variable.

We can see above that the JAVA_HOME variable is not set, and the PATH specifies /user/bin for example:

Result:

Result:

We can use server.env files at the install and server levels to specify environment variables such as JAVA_HOME, WLP_USER_DIR, and WLP_OUTPUT_DIR. These files support only KEY=value pairs. Shell and variable expansion are not supported.

The server management script will search for server.env files in two locations, ${wlp.install.dir}/etc/server.env and ${server.config.dir}/server.env. If both files are present, the contents of the two server.env files will be merged, with values in the the server-level file taking precedence over values in the runtime-level file.

Steps:

We will use a variable fro JAVA_HOME in a file called server.env, in this example it will be placed in the <installroot/>etc/server.env for example: /var/apps/wasnd855_lp/etc

• Stop the server.
  
• Create a file called /var/apps/wasnd855_lp/etc/server.env
  

• Edit the file with your favourite editor (I just logged in using WinSCP an used the default text editor) and set the JAVA_HOME variable to point to the JRE you want to use for example:
  

• Close the file and save your changes.
  
• Start the server
  

• Check the console.log
  

Result:

Note that the version of the JRE listed in the console window now references the IBM 8 JRE Java version, as opposed to the current shell’s Java version.