SecurityManager sm = System.getSecurityManager();
if (sm != null) sm.checkPermission(GET_CONTEXT);
Callers threadLocalCallers = callers.get();
assert threadLocalCallers != null : "No current callers";
Subject currentSubject = threadLocalCallers.getCurrentCaller();
assert currentSubject != null : "No current caller";
Context context = subjectContexts.get(currentSubject);
assert context != null : "No registered context";