java 线程池中 execute 和 submit 方法的区别

ThreadPoolExecutor UML类图

execute 方法定义

public interface Executor {
    void execute(Runnable command);
}

submit 方法定义

public interface ExecutorService extends Executor {
  <T> Future<T> submit(Callable<T> task);

  <T> Future<T> submit(Runnable task, T result);
  
  Future<?> submit(Runnable task);
}

submit 方法具体实现

public abstract class AbstractExecutorService implements ExecutorService {
    public Future<?> submit(Runnable task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<Void> ftask = newTaskFor(task, null);
        execute(ftask);
        return ftask;
    }
    
    public <T> Future<T> submit(Runnable task, T result) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<T> ftask = newTaskFor(task, result);
        execute(ftask);
        return ftask;
    }
    
    public <T> Future<T> submit(Callable<T> task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<T> ftask = newTaskFor(task);
        execute(ftask);
        return ftask;
    }
}

execute 方法具体实现

public class ThreadPoolExecutor extends AbstractExecutorService {
  public void execute(Runnable command) {
    // 具体实现
  }
}

程序验证

public class ExecuteVsSubmit {
    public static final SimpleDateFormat SDF = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");

    // 线程池核心线程最大线程数
    private static final int MAX_THREAD_SIZE = 10;

    public static void main(String[] args) throws Exception {
        // 模拟请求列表
        List<String> requests = Lists.newArrayList("A0001", "A0002", "A0003", "A0004", "A0005", "B0001", "B0002", "B0003", "B0004", "B0005");
        ExecutorService executor = Executors.newFixedThreadPool(requests.size() > MAX_THREAD_SIZE ? MAX_THREAD_SIZE : requests.size());

        // 只在 submit 方式-2 和 submit 方式-3 中用到
        List<Future<Response>> futures = new ArrayList<>();

        System.out.println(SDF.format(new Date()) + " 发送请求~~~");

        for (String request : requests) {
            // execute 方式 (第二个参数意义不大, 可以参考 `submit 方式-2-2` 的调用方式)
//            executor.execute(new TaskRunnable(request, new Response()));

            // submit 方式-1 (第二个参数意义不大, 可以参考 `submit 方式-2-2` 的调用方式)
//            executor.submit(new TaskRunnable(request, new Response()));

            // submit 方式-2-1
//            Response response = new Response();
//            Future<Response> future = executor.submit(new TaskRunnable(request, response), response);
//            futures.add(future);

            // submit 方式-2-2
            Response response = new Response();
            Future<Response> future = executor.submit(() -> {
                System.out.println(String.format("%s 异步请求接口=[%s]",
                        ExecuteVsSubmit.SDF.format(new Date()), request));

                try {
                    Thread.sleep(5 * 1000);
                    response.setMsg(request);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }, response);
            futures.add(future);

            // submit 方式-3
//            Future<Response> future = executor.submit(new TaskCallable(request));
//            futures.add(future);
        }


        // 获取异步结果
        for (Future<Response> future : futures) {
            System.out.println(SDF.format(new Date()) + " 结果=" + future.get().getMsg());
        }

        executor.shutdown();
    }

}


class TaskCallable implements Callable<Response> {
    private String request;

    public TaskCallable(String request) {
        this.request = request;
    }

    @Override
    public Response call() throws Exception {
        System.out.println(String.format("%s 异步请求接口=[%s]",
                ExecuteVsSubmit.SDF.format(new Date()), this.request));

        try {
            Thread.sleep(5 * 1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return new Response(request);
    }
}

class TaskRunnable implements Runnable {
    private String request;
    private Response response;

    public TaskRunnable(String request, Response response) {
        this.request = request;
        this.response = response;
    }

    @Override
    public void run() {
        System.out.println(String.format("%s 异步请求接口=[%s]",
                ExecuteVsSubmit.SDF.format(new Date()), this.request));

        try {
            Thread.sleep(5 * 1000);
            response.setMsg(request);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

@Data
@NoArgsConstructor
@AllArgsConstructor
class Response {
    private String msg;
}

• execute和submit都属于线程池的方法，execute只能提交Runnable类型的任务，而submit既能提交Runnable类型任务也能提交Callable类型任务。
• execute会直接抛出任务执行时的异常，submit会吃掉异常，可通过Future的get方法将任务执行时的异常重新抛出。
• execute所属顶层接口是Executor,submit所属顶层接口是ExecutorService，实现类ThreadPoolExecutor重写了execute方法,抽象类AbstractExecutorService重写了submit方法。