A Hacky Way to Clean All Thread Local Variables of Current Thread

gistfile1.java

void cleanThreadLocalsOfCurrentThread() {
   try {
      // Get a reference to the thread locals table of the current thread
      Thread thread = Thread.currentThread();
      Field threadLocalsField = Thread.class.getDeclaredField("threadLocals");
      threadLocalsField.setAccessible(true);
      Object threadLocalTable = threadLocalsField.get(thread);

      // Get a reference to the array holding the thread local variables inside the 
      // ThreadLocalMap of the current thread
      Class threadLocalMapClass = Class.forName("java.lang.ThreadLocal$ThreadLocalMap");
      Field tableField = threadLocalMapClass.getDeclaredField("table");
      tableField.setAccessible(true);
      Object table = tableField.get(threadLocalTable);

      // The key to the ThreadLocalMap is a WeakReference object. The referent field of this object
      // is a reference to the actual ThreadLocal variable
      Field referentField = Reference.class.getDeclaredField("referent");
      referentField.setAccessible(true);

      for (int i = 0; i < Array.getLength(table); i++) {
         // Each entry in the table array of ThreadLocalMap is an Entry object
         // representing the thread local reference and its value
         Object entry = Array.get(table, i);
         if (entry != null) {
            // Get a reference to the thread local object and remove it from the table
            ThreadLocal threadLocal = (ThreadLocal) referentField.get(entry);
            threadLocal.remove();
         }
      }
   } catch(Exception e) {
       // No way to handle, just throw it
      throw new IllegalStateException(e);
   }
}