How do I change the Java version used by Jenkins?

Question

I am trying to change the version of Java used by Jenkins from Java 8 to Java 11. Jenkins is running on Windows Server 2016. I've installed the Java 11 SDK. I have tried creating a system environment variable JAVA_HOME pointing to my Java 11 installation (per instructions https://www.jenkins.io/doc/administration/requirements/upgrade-java-guidelines). I have also tried updating the Jenkins.xml file to point to the Java 11 installation. I was unable to access the Jenkins server after trying either of these methods (although it looked like the Jenkins service was running). How can I point my Jenkins service to my new Java 11 installation?

Jenkins was installed about a year ago using instructions in the Docs (https://www.jenkins.io/doc/book/installing/windows). It is installed as a service.

Current version: 2.346.3 Version of JDK installed: 11.0.16.1

The Java 8 version was installed (jre) with the original Jenkins install. The Java 11 version (JDK) was installed separately.

Here is my original Jenkins.xml file:

<service>
  <id>Jenkins</id>
  <name>Jenkins</name>
  <description>This service runs Jenkins automation server.</description>
  <env name="JENKINS_HOME" value="C:\Jenkins\Workspace"/>

 <!--if you'd like to run Jenkins with a specific version of Java, specify a full path to java.exe.
The following value assumes that you have java in your PATH.-->

  <executable>%BASE%\jre\bin\java</executable>
  <arguments>-Xrs -Xmx256m -Dhudson.lifecycle=hudson.lifecycle.WindowsServiceLifecycle -jar "%BASE%\jenkins.war" --httpPort=8080 --webroot="%BASE%\war"</arguments>

  <logmode>rotate</logmode>

  <onfailure action="restart" /> 
   <extensions>
    <extension enabled="true" 
               className="winsw.Plugins.RunawayProcessKiller.RunawayProcessKillerExtension"
               id="killOnStartup">
      <pidfile>%BASE%\jenkins.pid</pidfile>
      <stopTimeout>10000</stopTimeout>
      <stopParentFirst>false</stopParentFirst>
    </extension>
  </extensions>  
</service>

Answer 1

Try to change this line

<executable>%BASE%\jre\bin\java</executable>

or change %BASE% variable. Also I would recommend to remove java 8 if it used only by jenkins.

Answer 2

I think our jenkins.xml is unmodified:

    <!--
    The MIT License

    Copyright (c) 2004-2017, Sun Microsystems, Inc., Kohsuke Kawaguchi, Oleg Nenashev, and other Jenkins contributors

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    THE SOFTWARE.
    -->

    <!--
      Windows service definition for Jenkins.

      To uninstall, run "jenkins.exe stop" to stop the service, then "jenkins.exe uninstall" to uninstall the service.
      Both commands don't produce any output if the execution is successful. 
    -->
    <service>
      <id>jenkins</id>
      <name>Jenkins</name>
      <description>This service runs Jenkins automation server.</description>
      <env name="JENKINS_HOME" value="%BASE%"/>
     <!--
    if you'd like to run Jenkins with a specific version of Java, specify a full path to java.exe.
    The following value assumes that you have java in your PATH.
      -->
      <executable>java</executable>
    <arguments>-Xrs -Xmx1024m -Dcom.sun.management.jmxremote.port=9010 -Dcom.sun.management.jmxremote.local.only=false -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dhudson.lifecycle=hudson.lifecycle.WindowsServiceLifecycle -jar "%BASE%\jenkins.war" --webroot="%BASE%\war" --httpsPort=443 --httpsKeyStore="c:\path\to\keystore.jks" --httpsKeyStorePassword="****"    </arguments>
 
      <!--
    interactive flag causes the empty black Java window to be displayed.
    I'm still debugging this.
  <interactive />
  -->
  <logmode>rotate</logmode>

  <onfailure action="restart" />
  
  <!-- 
    In the case WinSW gets terminated and leaks the process, we want to abort
    these runaway JAR processes on startup to prevent corruption of JENKINS_HOME.
    So this extension is enabled by default.
  -->
  <extensions>
    <!-- This is a sample configuration for the RunawayProcessKiller extension. -->
    <extension enabled="true" 
               className="winsw.Plugins.RunawayProcessKiller.RunawayProcessKillerExtension"
               id="killOnStartup">
      <pidfile>%BASE%\jenkins.pid</pidfile>
      <stopTimeout>10000</stopTimeout>
      <stopParentFirst>false</stopParentFirst>
    </extension>
  </extensions>
  
  <!-- See the referenced examples for more options -->
  
</service>

I think the relavant hint is if you'd like to run Jenkins with a specific version of Java, specify a full path to java.exe. The following value assumes that you have java in your PATH.

So I just added JAVA11_HOME as a system variable and put %JAVA11_HOME%\binin front of the PATH system environment variable.