如何为 parallelStream 设置 ThreadLocal

Question

我有一个线程，它包含ThreadLocal 变量。我需要在上述线程中使用parallelStream()。需要调用使用线程局部变量的myService。在 java8 中使用parallelstream() 时是否有任何机制来设置ThreadLocal。

List<MyObject> result = myList.parallelStream().map(myObject -> {
    //call myService with the Threadlocal 
}).filter(...)
.....;

Answer 1

您可以在调用服务之前轻松设置 threadLocal 变量。在地图中，您可以从主线程本地值或任何其他值中设置值。

 ThreadLocal<String> threadLocal= new ThreadLocal<>();

        IntStream.range(0, 8).parallel().forEach(n -> {
            threadLocal.set("MAIN");
            System.out.println("This is sequence access "+n);
            System.out.printf("Service used ThreadLocal - %d: %s\n", n, threadLocal.get());
        });

结果：

This is sequence access 5
This is sequence access 7
Parallel Consumer - 5: MAIN
Parallel Consumer - 7: MAIN
This is sequence access 4
This is sequence access 6
Parallel Consumer - 4: MAIN
Parallel Consumer - 6: MAIN
This is sequence access 2
This is sequence access 1
Parallel Consumer - 2: MAIN
This is sequence access 0
This is sequence access 3
Parallel Consumer - 0: MAIN
Parallel Consumer - 1: MAIN
Parallel Consumer - 3: MAIN