Package com.alibaba.ttl

Class TransmittableThreadLocal.Transmitter

  • Enclosing class:
    TransmittableThreadLocal<T>
    public static class TransmittableThreadLocal.Transmitter
extends Object
    TransmittableThreadLocal.Transmitter transmit all TransmittableThreadLocal values of current thread to other thread by static methods capture() => replay(Object) => restore(Object) (aka CRR operation).

    TransmittableThreadLocal.Transmitter is internal manipulation api for framework/middleware integration; In general, you will never use it in the biz/application code!

    Below is the example code: 

    
 ///////////////////////////////////////////////////////////////////////////
 // in thread A, capture all TransmittableThreadLocal values of thread A
 ///////////////////////////////////////////////////////////////////////////

 Object captured = Transmitter.capture(); // (1)

 ///////////////////////////////////////////////////////////////////////////
 // in thread B
 ///////////////////////////////////////////////////////////////////////////

 // replay all TransmittableThreadLocal values from thread A
 Object backup = Transmitter.replay(captured); // (2)
 try {
     // your biz logic, run with the TransmittableThreadLocal values of thread B
     System.out.println("Hello");
     // ...
     return "World";
 } finally {
     // restore the TransmittableThreadLocal of thread B when replay
     Transmitter.restore(backup); (3)
 }

    see the implementation code of TtlRunnable and TtlCallable for more actual code sample.

    Of course, replay(Object) and restore(Object) operation can be simplified by util methods runCallableWithCaptured(Object, Callable) or runSupplierWithCaptured(Object, Supplier) and the adorable Java 8 lambda syntax.

    Below is the example code: 

    
 ///////////////////////////////////////////////////////////////////////////
 // in thread A, capture all TransmittableThreadLocal values of thread A
 ///////////////////////////////////////////////////////////////////////////

 Object captured = Transmitter.capture(); // (1)

 ///////////////////////////////////////////////////////////////////////////
 // in thread B
 ///////////////////////////////////////////////////////////////////////////

 String result = runSupplierWithCaptured(captured, () -> {
      // your biz logic, run with the TransmittableThreadLocal values of thread A
      System.out.println("Hello");
      ...
      return "World";
 }); // (2) + (3)

    The reason of providing 2 util methods is the different throws Exception type so as to satisfy your biz logic(lambda):

    1. runCallableWithCaptured(Object, Callable): throws Exception
    2. runSupplierWithCaptured(Object, Supplier): No throws

    If you need the different throws Exception type, you can define your own util method(function interface(lambda)) with your own throws Exception type.

    Since:
    2.3.0
    Author:
    Yang Fang (snoop dot fy at gmail dot com), Jerry Lee (oldratlee at gmail dot com)
    See Also:
    TtlRunnable, TtlCallable