jdk20 新特性 scoped value 的使用

注意:由于使用方式的限制,这种值的传递只能单向
由于特性还在孵化阶段 用法可能在21中有变动

    static final ScopedValue<Long> scopedValue = ScopedValue.newInstance();
    // test scoped value
    @Test
    public void testScopedValue() throws InterruptedException {


        CountDownLatch latch = new CountDownLatch(1);

        Thread start = Thread.ofVirtual().start(() -> {
            ScopedValue.where(scopedValue, System.currentTimeMillis(), this::showMessage);
            latch.countDown();
        });
        latch.await();
        //此处会报错,因为线程start中的scopedValue已经被移除,生命周期之外scoped value不能被访问
        System.out.println(scopedValue.get());

    }


    //此处可以在内部调用其他方法并获取scoped value,因为scopedValue已经被绑定到当前线程,注意传递是单向的,内部的变更无法在上一级获取
    //此处代码来自 https://github.com/hakdogan/scoped-values
    void showMessage() {
      log.info(scopedValue.get().toString());
        //       Long request = scopedValue.get();
        //
        //        try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
        //            Future<Boolean> validation  = scope.fork(() -> xxx);
        //            Future<Boolean> account = scope.fork(() -> xxx);
        //
        //            try {
        //                scope.join();
        //                scope.throwIfFailed();
        //            } catch (InterruptedException e) {
        //                Thread.currentThread().interrupt();
        //                throw new RuntimeException("This thread was interrupted!");
        //            } catch (ExecutionException e){
        //                throw new RuntimeException("An ExecutionException occurred!");
        //            }
        //
        //            if(validation.resultNow() && account.resultNow()){
        //                getPaid();
        //                ScopedValue.where(scopedValue, xxx)
        //                        .run(() -> xxx);
        //            }
        //        }
    }

idea 配置

--enable-preview -source 20 --add-modules jdk.incubator.concurrent

官方描述