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Catalyst can use Java installed on the system, Java from JAVA_HOME, Java found on PATH, common platform install locations, managed Catalyst runtimes, or a per-server custom executable.

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Version mapping

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Runtime selection order

1

Use custom Java when set

A server-specific Java executable path takes priority.
2

Search installed runtimes

Catalyst checks managed runtimes, JAVA_HOME, PATH, and common install directories.
3

Download if needed

When no compatible runtime is found, Catalyst can download an Adoptium JDK for the required major version.
4

Start with matching JAVA_HOME

Managed or custom runtimes set the process environment so Java tools resolve consistently.

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Managed runtimes

Managed runtimes are stored under:
Downloads use the Adoptium binary API and include timeout, stall, extraction, and checksum handling when the upstream response provides checksum information.
Changing a server’s Java path does not affect running processes. Restart the server after saving the setting.