Windows
Stop Tomcat
See Tomcat start/ stop, open properties
Install new Java version
Follow instructions to install Java: https://phixflow.atlassian.net/wiki/pages/createpage.action?spaceKey=HELP83&title=Install%20Java%20OLD Install Java
Update JAVA_HOME
If you have set the environment variable JAVA_HOME, check whether this needs updating in the system environment variables. Commonly this will be automatically updated by the installation process.
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If you are migrating to a new major version of Java (e.g. you are moving from Java 8 to Java 11), you will need to remove the previous version from the list of installed programs.
Start Tomcat
See Tomcat start/ stop, open properties
Linux
Stop Tomcat
See Tomcat start/ stop, open properties
Minor (patch) upgrades
If you have installed Java as recommended by PhixFlow (Install Java), upgrade Java as recommended for any package installed using the package manager. For example, on Debian based distributions of linux, the generally recommended approach is by using dist-upgrade.
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If you have moved from Java 8 to Java 11, updateCATALINAupdate CATALINA_OPTS in /etc/systemd/system/tomcat.service as instructed here: Install Tomcat on Linux