The problem here is starting up the GAE process with the JRebel JVM arguments or in general adding JVM arguments to the GAE process.
There are multiple ways of adding JVM arguments to the process, I would recommend adding those arguments to the appengine plugin
You can set JVM arguments for JRebel in your pom.xml:
<plugin>
<groupId>com.google.appengine</groupId>
<artifactId>appengine-maven-plugin</artifactId>
<version>${appengine.target.version}</version>
<configuration>
<jvmFlags>
<jvmFlag>-agentpath:{jrebel install directory}/lib/libjrebel64.dylib</jvmFlag>
</jvmFlags>
<disableUpdateCheck>true</disableUpdateCheck>
</configuration>
</plugin>
Where libjrebel64.dylib
works for macOS, and you'd use libjrebel64.so
on Linux and jrebel64.dll
on Windows.