java - Resolving Dependencies in JNI DefineClass -

i writing application using jvmti. trying instrument bytecode: injecting method calls on every method entry.

i know how that, problem in instrument class, it's called proxy, load using jni function defineclass. proxy has few dependencies in java class library, java.lang.threadlocal<boolean>.

now, have this, ininstrumentmethod plain boolean:

public static void onentry(int methodid) {     if (ininstrumentmethod) {         return;     } else {         ininstrumentmethod = true;     }      system.out.println("method id: " + methodid);      ininstrumentmethod = false; } 

the code compiles , works. however, if make ininstrumentmethod java.lang.threadlocal<boolean>, noclassdeffounderror. code:

private static threadlocal<boolean> ininstrumentmethod = new threadlocal<boolean>() {         @override protected boolean initialvalue() {             return boolean.false;         }     };  public static void onentry(int methodid) {     if (ininstrumentmethod.get()) {         return;     } else {         ininstrumentmethod.set(true);     }      system.out.println("method id: " + methodid);      ininstrumentmethod.set(false); } 

my guess dependencies have not been resolved correctly, , java.lang.threadlocal not loaded (and not found). question is, then, how force java load java.lang.threadlocal? don't think use defineclass in case; there alternative?

i don’t think there problem resolving standard class java.lang.threadlocal, rather inner class extending it, generated by

new threadlocal<boolean>() {     @override protected boolean initialvalue() {         return boolean.false;     } }; 

solving via defineclass might indeed impossible due circular dependency between inner , outer class, there’s no order allows define them, unless have full-fledged classloader returns classes on demand.

the simplest solution avoid generation of inner class @ all, possible java 8:

private static threadlocal<boolean> ininstrumentmethod                                   = threadlocal.withinitial(() -> boolean.false); 

if use version prior java 8, can’t use way, best solution in case, rewrite code accept default value of null initial value, eliminating need specify different initial value:

private static threadlocal<boolean> ininstrumentmethod = new threadlocal<>();  public static void onentry(int methodid) {     if (ininstrumentmethod.get()!=null) {         return;     } else {         ininstrumentmethod.set(true);     }      system.out.println("method id: " + methodid);      ininstrumentmethod.set(null); } 

you convert anonymous inner class top level class. since then, class has no dependency formerly outer class, defining subtype of threadlocal first, before defining class using it, should solve issue.