Java并发编程新突破：结构化并发与虚拟线程实战指南

一、虚拟线程核心原理

轻量级线程的革新性实现：

// 虚拟线程基础使用
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
    IntStream.range(0, 10_000).forEach(i -> {
        executor.submit(() -> {
            Thread.sleep(Duration.ofSeconds(1));
            System.out.println(i);
            return i;
        });
    });
}

// 与传统线程池对比
// 传统线程池（平台线程）
ExecutorService oldPool = Executors.newFixedThreadPool(200); 

// 虚拟线程池
ExecutorService virtualPool = Executors.newVirtualThreadPerTaskExecutor();

// 自定义虚拟线程
Thread.Builder builder = Thread.ofVirtual()
    .name("worker-", 0)
    .inheritInheritableThreadLocals(false);

Thread virtualThread = builder.unstarted(() -> {
    System.out.println("Running in virtual thread");
});
virtualThread.start();

核心优势：轻量级（1MB可创建百万线程）、自动调度、兼容现有API、低延迟

二、结构化并发实战

1. 任务生命周期管理

// 结构化并发基本用法
Response handleRequest() throws Exception {
    try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
        Future user = scope.fork(() -> fetchUser());
        Future order = scope.fork(() -> fetchOrder());
        
        scope.join();           // 等待所有子任务
        scope.throwIfFailed();  // 检查异常
        
        return new Response(user.resultNow(), order.resultNow());
    }
}

// 超时控制
try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
    Future future = scope.fork(() -> queryDatabase());
    
    scope.joinUntil(Instant.now().plusSeconds(3));
    if (future.state() == Future.State.RUNNING) {
        scope.shutdown();  // 取消所有子任务
        throw new TimeoutException();
    }
}

2. 复杂任务编排

// 多阶段任务处理
void processOrder(Order order) throws Exception {
    try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
        // 第一阶段：验证
        Future validate = scope.fork(() -> validate(order));
        Future checkStock = scope.fork(() -> checkInventory(order));
        
        scope.join();
        if (!validate.resultNow()) {
            throw new ValidationException();
        }

        // 第二阶段：执行
        try (var innerScope = new StructuredTaskScope.ShutdownOnFailure()) {
            Future payment = innerScope.fork(() -> charge(order));
            Future shipping = innerScope.fork(() -> scheduleDelivery(order));
            
            innerScope.join();
            sendConfirmation(
                payment.resultNow(), 
                shipping.resultNow()
            );
        }
    }
}

三、性能优化策略

1. 虚拟线程调优

// 虚拟线程创建选项
Thread.Builder builder = Thread.ofVirtual()
    .name("worker-", 0)    // 命名模板
    .allowSetThreadLocals(false)  // 禁用ThreadLocal
    .inheritInheritableThreadLocals(false);

// 执行策略配置
ExecutorService executor = Executors.newThreadPerTaskExecutor(
    Thread.ofVirtual()
        .factory()
        .withScheduler(ForkJoinPool.commonPool())
);

// 系统属性调优
-Djdk.virtualThreadScheduler.parallelism=32
-Djdk.virtualThreadScheduler.maxPoolSize=256
-Djdk.virtualThreadScheduler.minRunnable=4

2. 异步IO整合

// 虚拟线程+异步HTTP客户端
HttpClient client = HttpClient.newBuilder()
    .executor(Executors.newVirtualThreadPerTaskExecutor())
    .build();

List<CompletableFuture> futures = urls.stream()
    .map(url -> client.sendAsync(
        HttpRequest.newBuilder(URI.create(url)).build(),
        HttpResponse.BodyHandlers.ofString()
    ).thenApply(HttpResponse::body))
    .toList();

// 结构化并发包装
try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
    List<Future> results = futures.stream()
        .map(future -> scope.fork(future::join))
        .toList();
    
    scope.join();
    return results.stream().map(Future::resultNow).toList();
}

四、电商系统实战案例

1. 高并发库存服务

// 库存扣减服务
public class InventoryService {
    private final ReentrantLock lock = new ReentrantLock();
    
    @Transactional
    public void deduct(String itemId, int quantity) {
        try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
            // 并行检查
            Future available = scope.fork(
                () -> checkAvailable(itemId, quantity));
            Future frozen = scope.fork(
                () -> checkFrozen(itemId));
            
            scope.join();
            if (!available.resultNow() || frozen.resultNow()) {
                throw new InventoryException();
            }

            // 加锁扣减
            lock.lock();
            try {
                updateStock(itemId, -quantity);
                createRecord(itemId, quantity);
            } finally {
                lock.unlock();
            }
        }
    }
}

// 批量查询优化
public List batchQuery(List ids) {
    try (var scope = new StructuredTaskScope.ShutdownOnSuccess()) {
        List<Future> futures = ids.stream()
            .map(id -> scope.fork(() -> queryProduct(id)))
            .toList();
        
        return scope.join()
            .stream()
            .flatMap(f -> Stream.of(f.resultNow()))
            .toList();
    }
}