Runnable JAR files

Runnable JAR files contain applications, server configurations, and an Open Liberty installation.

For information about packaging a JAR, see the server package command.

When a JAR file runs, it gets extracted to a temporary location and the server runs in the foreground. By default, files are extracted to wlpExtract/<jar file name>_nnnnnnnnnnnnnnnnnnn in the user home directory. You can control the output location by using the WLP_JAR_EXTRACT_ROOT or WLP_JAR_EXTRACT_DIR environment variables.

Variable syntax

When you run Open Liberty from a runnable JAR file you can define variables at startup by using the following syntax:

java -jar myServer.jar --variable1_name=variable1_value --variable2_name=variable2_value

You can specify multiple variables with this format. Variables that are specified on the command line override all other sources of variables and can’t be changed after the server starts.

Environment variables

For information about specifying environment variables, see Server configuration overview. The following table lists environmental variables that you can specify to work with runnable JAR files. Column one contains the environmental variable and column two contains a description of the variable.

Environmental variables for runnable JAR files
Environment variable nameDescription

WLP_JAR_EXTRACT_ROOT

Extracts the JAR file to the ${WLP_JAR_EXTRACT_ROOT}/<jar file name>_nnnnnnnnnnnnnnnnnnn directory.

WLP_JAR_EXTRACT_DIR

Extracts the JAR file to the ${WLP_JAR_EXTRACT_DIR} directory.

WLP_OUTPUT_DIR

Writes Open Liberty server output files to the ${WLP_OUTPUT_DIR} directory.

By default, server output is written to the extraction directory, which is deleted when the server stops. If you want to save the output, specify a durable output location by using the WLP_OUTPUT_DIR environment variable before you start the server.

WLP_JAR_DEBUG

Runs an Open Liberty server by using server debug <server name> instead of server run <server name>. You can run the server in debug mode if you set the WLP_JAR_DEBUG environment variable before you start the server.

WLP_JAR_ENABLE_2PC

Set to value true to enable two-phase commit transactions when the runnable JAR file runs.

By default, two-phase commit transactions are disabled because the transaction logs are in the expansion directory and are deleted when the Open Liberty server stops. Therefore, transaction recovery is not possible.

To enable two-phase commit transactions, configure the transaction log to be in a durable location in the file system or an RDBMS, and set the WLP_JAR_ENABLE_2PC environment variable.

To configure the transaction log, use either the transactionLogDirectory or dataSourceRef attributes on the transaction element in your server.xml config.

WLP_JAR_CYGWIN

Set to value true if you are running the JAR file under CYGWIN. This variable causes the Open Liberty server JAR runner to do UNIX-style file and UNIX-style process handling when it is running in the CYGWIN environment.

Run under the bash shell, not mintty. Automatic extraction file deletion occurs only when you run under the bash shell. You can run under mintty, but you must delete the extraction files manually. Mintty does not forward the necessary signal that is required to trigger Java shutdown hooks.

See also