要有最朴素的梦想，即使明天天寒地冻，路远马亡。——海子
前段时间遇到的TTL(TransmittableThreadLocal)在异步编程中的上下文丢失问题，我是采用了直接更换线程池的方式
但今天抽空看了下官方文档，发现了：
CRR：capture(快照)、replay(回放)、restore(备份)
自己简单写了个测试用例，用于在CompletableFuture和并行流场景下解决ThreadLocal的上下文丢失问题
大伙一定要复制到本地跑一下，需要的GAV是这个：
<dependency> <groupId>com.alibaba</groupId> <artifactId>transmittable-thread-local</artifactId> <version>2.12.4</version> </dependency>
代码：
import com.alibaba.ttl.TransmittableThreadLocal; import lombok.SneakyThrows; import org.junit.Ignore; import org.junit.jupiter.api.Assertions; import org.junit.Test; import java.util.concurrent.CompletableFuture; import java.util.stream.Stream; /** * TTL单元测试 * * @author <achao1441470436@gmail.com> * @since 2022/1/24 18:41 */ public class TtlTest { @Test @SneakyThrows public void testCompletableFuture() { ThreadLocal<Integer> threadLocal = new InheritableThreadLocal<>(); Stream.iterate(0, i -> ++i).limit(2).forEach(i -> { threadLocal.set(i); CompletableFuture.runAsync(() -> Assertions.assertEquals(i, threadLocal.get())).join(); threadLocal.remove(); }); } @Test @SneakyThrows public void testCompletableFutureReplayRestore() { ThreadLocal<Integer> threadLocal = new TransmittableThreadLocal<>(); Stream.iterate(0, i -> ++i).limit(2).forEach(i -> { threadLocal.set(i); // (1) 抓取当前线程的所有TTL值 final Object captured = TransmittableThreadLocal.Transmitter.capture(); CompletableFuture.runAsync(() -> { // 异步 // (2) 在线程 B中回放在capture方法中抓取的TTL值，并返回 回放前TTL值的备份 final Object backup = TransmittableThreadLocal.Transmitter.replay(captured); try { // 你的业务逻辑，这里你可以获取到外面设置的TTL值 Assertions.assertEquals(i, threadLocal.get()); } finally { // (3) 恢复线程 B执行replay方法之前的TTL值（即备份） TransmittableThreadLocal.Transmitter.restore(backup); } }).join(); threadLocal.remove(); }); } @Test @SneakyThrows public void testCompletableFutureTransmitter() { ThreadLocal<Integer> threadLocal = new TransmittableThreadLocal<>(); Stream.iterate(0, i -> ++i).limit(2).forEach(i -> { threadLocal.set(i); // (1) 抓取当前线程的所有TTL值 final Object captured = TransmittableThreadLocal.Transmitter.capture(); CompletableFuture.runAsync(() -> // 异步 TransmittableThreadLocal.Transmitter.runSupplierWithCaptured(captured, () -> { // 你的业务逻辑，这里你可以获取到外面设置的TTL值 Assertions.assertEquals(i, threadLocal.get()); return null; })).join(); threadLocal.remove(); }); } @Test public void testParallelStream() { ThreadLocal<Integer> threadLocal = new TransmittableThreadLocal<>(); Stream.iterate(0, i -> ++i).limit(1).peek(threadLocal::set) .flatMap(item -> Stream.of(item, item).parallel().peek(i -> Assertions.assertEquals(i, threadLocal.get()))) .peek(t -> threadLocal.remove()).forEach(System.out::println); } @Test public void testParallelStreamReplayRestore() { ThreadLocal<Integer> threadLocal = new TransmittableThreadLocal<>(); Stream.iterate(0, i -> ++i).limit(1).peek(threadLocal::set) .flatMap(item -> { // (1) 抓取当前线程的所有TTL值 final Object captured = TransmittableThreadLocal.Transmitter.capture(); return Stream.of(item, item).parallel().peek(i -> { // 异步 // (2) 在线程 B中回放在capture方法中抓取的TTL值，并返回 回放前TTL值的备份 final Object backup = TransmittableThreadLocal.Transmitter.replay(captured); try { // 你的业务逻辑，这里你可以获取到外面设置的TTL值 Assertions.assertEquals(i, threadLocal.get()); } finally { // (3) 恢复线程 B执行replay方法之前的TTL值（即备份） TransmittableThreadLocal.Transmitter.restore(backup); } }); }) .peek(t -> threadLocal.remove()).forEach(System.out::println); } @Test public void testParallelStreamTransmitter() { ThreadLocal<Integer> threadLocal = new TransmittableThreadLocal<>(); Stream.iterate(0, i -> ++i).limit(1).peek(threadLocal::set) .flatMap(item -> { // (1) 抓取当前线程的所有TTL值 final Object captured = TransmittableThreadLocal.Transmitter.capture(); return Stream.of(item, item).parallel().peek(i -> // 异步 TransmittableThreadLocal.Transmitter.runSupplierWithCaptured(captured, () -> { // 你的业务逻辑，这里你可以获取到外面设置的TTL值 Assertions.assertEquals(i, threadLocal.get()); return null; })); }) .peek(t -> threadLocal.remove()).forEach(System.out::println); } }
最后测试结果：
