public void execute(Runnable command) {
        Runnable associated = associateWithSubject(command);
        getTargetExecutor().execute(associated);
    }
Executes the specified runnable by first associating it with the currently executing {@code Subject} and then
dispatches the associated Runnable to the underlying target {@link Executor} instance.

@param command the runnable to associate with the currently executing subject and then to execute via the target
               {@code Executor} instance.
core/src/main/java/org/apache/shiro/concurrent/SubjectAwareExecutor.java