How can I add a Javaagent to a JVM without stopping the JVM?

Question

I wish to profile a Java application without stopping the application. Can I add a Javaagent somehow while the application is running?

Answer 1

See Starting a Java agent after program start.

It links to http://dhruba.name/2010/02/07/creation-dynamic-loading-and-instrumentation-with-javaagents/ that under "Dynamic loading of a javaagent at runtime" provides working example:

public static void loadAgent() throws Exception {
    String nameOfRunningVM = ManagementFactory.getRuntimeMXBean().getName();
    String pid = nameOfRunningVM.substring(0, nameOfRunningVM.indexOf('@'));
    VirtualMachine vm = VirtualMachine.attach(pid);
    vm.loadAgent(jarFilePath, "");
    vm.detach();
}

Note that Java 9 requires -Djdk.attach.allowAttachSelf=true to be present among JVM startup arguments.