com.alibaba.ttl

Class TransmittableThreadLocal.Transmitter

java.lang.Object

com.alibaba.ttl.TransmittableThreadLocal.Transmitter

Enclosing class:

TransmittableThreadLocal<T>

public static class TransmittableThreadLocal.Transmitter
extends Object

TransmittableThreadLocal.Transmitter transmit all TransmittableThreadLocal of current thread to any other thread by static method 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 1
 ///////////////////////////////////////////////////////////////////////////

 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 runCallableWithCaptured(Object, Callable) 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 from biz logic(@{code lambda}):

1. runCallableWithCaptured(Object, Callable): No throws
2. runSupplierWithCaptured(Object, Supplier): throws {@link Exception}

If you has the different throws Exception, you can define your own util method with your own throws Exception type function interface(@{code lambda}).

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

Constructor Summary

Constructors

Constructor and Description
Transmitter()

Method Summary

Modifier and Type	Method and Description
static Object	capture() Capture all TransmittableThreadLocal values in current thread.
static Object	replay(Object captured) Replay the captured TransmittableThreadLocal values from capture(), and return the backup TransmittableThreadLocal values in current thread before replay.
static void	restore(Object backup) Restore the backup TransmittableThreadLocal values from replay(Object).
static <R> R	runCallableWithCaptured(Object captured, Callable<R> bizLogic) Util method for simplifying replay(Object) and restore(Object) operation.
static <R> R	runSupplierWithCaptured(Object captured, Supplier<R> bizLogic) Util method for simplifying replay(Object) and restore(Object) operation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Transmitter

public Transmitter()

Method Detail

capture

public static Object capture()

Capture all TransmittableThreadLocal values in current thread.

Returns:

the captured TransmittableThreadLocal values

Since:

2.3.0

replay

public static Object replay(Object captured)

Replay the captured TransmittableThreadLocal values from capture(), and return the backup TransmittableThreadLocal values in current thread before replay.

Parameters:

captured - captured TransmittableThreadLocal values from other thread from capture()

Returns:

the backup TransmittableThreadLocal values before replay

Since:

2.3.0

See Also:

capture()

restore

public static void restore(Object backup)

Restore the backup TransmittableThreadLocal values from replay(Object).

Parameters:

backup - the backup TransmittableThreadLocal values from replay(Object)

Since:

2.3.0

runSupplierWithCaptured

public static <R> R runSupplierWithCaptured(Object captured,
                                            Supplier<R> bizLogic)

Util method for simplifying replay(Object) and restore(Object) operation.

Type Parameters:

R - the return type of biz logic

Parameters:

captured - captured TransmittableThreadLocal values from other thread from capture()

bizLogic - biz logic

Returns:

the return value of biz logic

Since:

2.3.1

See Also:

capture(), replay(Object), restore(Object)

runCallableWithCaptured

public static <R> R runCallableWithCaptured(Object captured,
                                            Callable<R> bizLogic)
                                     throws Exception

Util method for simplifying replay(Object) and restore(Object) operation.

Type Parameters:

R - the return type of biz logic

Parameters:

captured - captured TransmittableThreadLocal values from other thread from capture()

bizLogic - biz logic

Returns:

the return value of biz logic

Throws:

Exception - exception threw by biz logic

Since:

2.3.1

See Also:

capture(), replay(Object), restore(Object)