CompletableFuture的使用

CompletableFuture实现了Future和CompletionStage接口，提供了丰富的异步编程能力：

• 支持任务链式调用
• 提供多任务组合操作
• 内置异常处理机制
• 可以指定执行线程池

实际应用示例

public class AsyncService {
    private final ThreadPoolExecutor executor;
    
    public AsyncService() {
        // 创建IO密集型任务的线程池
        int processors = Runtime.getRuntime().availableProcessors();
        executor = new ThreadPoolExecutor(
            processors * 2,
            processors * 4,
            60, TimeUnit.SECONDS,
            new LinkedBlockingQueue<>(1000),
            new ThreadFactory() {
                private final AtomicInteger counter = new AtomicInteger(1);
                @Override
                public Thread newThread(Runnable r) {
                    Thread thread = new Thread(r);
                    thread.setName("async-service-" + counter.getAndIncrement());
                    thread.setDaemon(true);
                    return thread;
                }
            },
            new ThreadPoolExecutor.CallerRunsPolicy()
        );
    }
    
    public CompletableFuture<User> getUserAsync(Long userId) {
        return CompletableFuture.supplyAsync(() -> {
            // 模拟数据库查询
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
            return new User(userId, "用户" + userId);
        }, executor);
    }
    
    public CompletableFuture<Order> getOrderAsync(Long orderId) {
        return CompletableFuture.supplyAsync(() -> {
            // 模拟数据库查询
            try {
                Thread.sleep(150);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
            return new Order(orderId, "订单" + orderId);
        }, executor);
    }
    
    // 并行查询用户和订单信息
    public CompletableFuture<UserOrderDetail> getUserOrderDetail(Long userId, Long orderId) {
        CompletableFuture<User> userFuture = getUserAsync(userId);
        CompletableFuture<Order> orderFuture = getOrderAsync(orderId);
        
        return userFuture.thenCombineAsync(orderFuture, 
            (user, order) -> new UserOrderDetail(user, order), executor);
    }
    
    // 记得在应用关闭时关闭线程池
    public void shutdown() {
        executor.shutdown();
    }
}