How to configure java app externally when some of the arguments configure with java command

I have a java app, that is run with command:

java -Xmx2g -jar app.jar

I cannot modify the way that java command is executed. Is there a way to add additional flags to the JVM? I tried to add JAVA_OPTS environment variable but it doesn't help. For example:

export JAVA_OPTS=-XX:+PrintFlagsFinal
java -Xmx2g -jar app.jar

Doesn't print flags.

Try _JAVA_OPTIONS, which is an undocumented feature that probably has been removed now, but, if this is possible at all, that's how to do it.

Otherwise, perhaps the java command being run is written just like that, which means it is looked up in your shell $PATH variable, which means you can change that, and make that run a script which invokes the actual java, whilst adding a couple of options.

You may try JAVA_TOOL_OPTIONS

export JAVA_TOOL_OPTIONS="-XX:+PrintFlagsFinal"

/test/jre/bin/java -cp . DiskSizeCalculation17

Picked up JAVA_TOOL_OPTIONS: -XX:+PrintFlagsFinal
[Global flags]
     intx ActiveProcessorCount                      = -1                                  {product}
    uintx AdaptiveSizeDecrementScaleFactor          = 4                                   {product}
    uintx AdaptiveSizeMajorGCDecayTimeScale         = 10                                  {product}
    uintx AdaptiveSizePausePolicy                   = 0                                   {product}
    uintx AdaptiveSizePolicyCollectionCostMargin    = 50                                  {product}
    uintx AdaptiveSizePolicyInitializingSteps       = 20                                  {product}
    uintx AdaptiveSizePolicyOutputInterval          = 0                                   {product}