如何引用线程，以及如何在ThreadLocal上进行验证

Question

I'm looking for verification on the following use of ThreadLocal .

I have a service, say ServiceA running on a set of processes, say processSetX in the system. Which processSetX will be on ServiceA isn't known until runtime and may vary. The processes in processSetX may run on different threads. ServiceA has to recognize all processes in processSetX the same way.

For this, I'm supposed to write an ID value, say, of type String, to thread local storage (TLS) of a new thread and read this value later on when needed. So, the ID of the first thread invoking ServiceA will be this ID for ServiceA to recognize them all. When this first thread starts another thread, it'll go onto this new thread's TLS and write this ID. From there on, every thread in this chain will pass this ID to the new one.

I'm looking to verify ThreadLocal is the way to work this.

I haven't used it before - I want to make sure.

TIA.

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EDIT:

is there a way to get the calling thread's reference?

eg.:

a thread, say threadX is making a call to, say methodA() . is there a way for methodA() to know "who" is calling it? if so - methodA() is able to invoke a getter method of threadX to read a value from its thread-local storage.

TIA

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EDIT-2:

Thread.currentThread() returns something like Thread[main,5,main] . this may collide across threads.

Answer 1

I think at first, you just need a normal member variable.

For example:

// Thread
public class CalledThread extends Thread {

    public String myId;

    public void run() {
    ....

// Caller
    CalledThread t = new CalledThread();
    t.myId = "the thread ID";
    t.start();

However, you won't be able to access myId once you start calling your service classes, so for that you could use a ThreadLocal .

In CalledThread assign the myId to your ThreadLocal in run .

threadLocal.set(myId)