控制器甚至在使用异步和可完成的未来之后等待

Question

我正在开发一个 Spring Boot 应用程序，我想在其中使用 CompletableFuture 和 @Async 注释使我的控制器异步。为了测试实现，我特意在服务方法中添加了一个 Thread.sleep() 调用。然而，即使使用这些异步方法，控制器在执行之前仍然需要等待一段时间。我已经验证我的控制器和服务在不同的线程上运行，正如它们不同的线程 ID 所证明的那样。我不确定为什么会这样，如果有任何关于如何解决此问题的见解或建议，我将不胜感激。

代码如下：

//controller
  @PostMapping
    public CompletableFuture<User> createUser(@RequestBody User user) {
        System.out.println(Thread.currentThread().getId()+"-----------------------------------"+System.currentTimeMillis()+"----------"+"inside controller");
        return userService.createUser(user);
    }

// 服务

   @Override
    @Async("asyncExecutor")
    public CompletableFuture<User> createUser(User user) {
        System.out.println(Thread.currentThread().getId()+"-----------------------------------"+System.currentTimeMillis()+"-------------inside services");
        return CompletableFuture.supplyAsync(() ->{
            try {
                Thread.sleep(1000000000);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
            System.out.println(Thread.currentThread().getId());
           return userRepository.save(user);
        });
    }

提供一些代码示例或有关您的实现的具体细节，以便更清楚地了解问题。

//输出

21-----------------------------------1683404458540----------inside controller
34-----------------------------------1683404458543-------------inside services
2023-05-07 01:51:28.812  WARN 36119 --- [nio-8080-exec-2] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.context.request.async.AsyncRequestTimeoutException]

Answer 1

Thread.sleep(1000000000);

对于（构建）测试来说似乎太多了......这指的是〜12（太阳）天！

这有效：

• 启动器

• “应用程序”：

  package com.example.demo;
  
  import java.util.UUID;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.TimeUnit;
  
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.beans.factory.annotation.Value;
  import org.springframework.boot.SpringApplication;
  import org.springframework.boot.autoconfigure.SpringBootApplication;
  import org.springframework.scheduling.annotation.Async;
  import org.springframework.scheduling.annotation.EnableAsync;
  import org.springframework.stereotype.Controller;
  import org.springframework.stereotype.Service;
  import org.springframework.web.bind.annotation.GetMapping;
  import org.springframework.web.bind.annotation.RequestParam;
  import org.springframework.web.bind.annotation.ResponseBody;
  
  import lombok.extern.slf4j.Slf4j;
  
  @EnableAsync
  @SpringBootApplication
  public class DemoApplication {
  
    public static void main(String[] args) {
      SpringApplication.run(DemoApplication.class, args);
    }
  
    @Slf4j
    @Service
    static class MyAsyService {
      @Value("${simulation.sleep.seconds:10}")
      private Long simSeconds;
  
      @Async
      CompletableFuture<String> doSomething(String req) throws InterruptedException {
        log.info("in service...");
        TimeUnit.SECONDS.sleep(simSeconds);
        log.info("...leaving service");
        return CompletableFuture.completedFuture(req + "_" + UUID.randomUUID());
      }
    }
  
    @Slf4j
    @Controller
    static class MyController {
      @Autowired
      MyAsyService service;
  
      @GetMapping("/hello")
      @ResponseBody
      CompletableFuture<String> hello(@RequestParam(required = false, defaultValue = "anonymous") String req)
          throws InterruptedException {
        log.info("in controller...");
        CompletableFuture<String> result = service.doSomething(req);
        log.info("...controller done!");
        return result;
      }
    }
  }
  

• 在浏览器中：

• 在服务器日志中：

  ... o.s.web.servlet.DispatcherServlet    : Completed initialization in 1 ms
  ... DemoApplication$MyController : in controller.... <= req#1
  ... DemoApplication$MyController : ....controller done!
  ... DemoApplication$MyAsyService : in service....
  ... DemoApplication$MyAsyService : ....leaving service
  ... DemoApplication$MyController : in controller.... <= req#2
  ... DemoApplication$MyController : ....controller done!
  ... DemoApplication$MyAsyService : in service....
  ... DemoApplication$MyAsyService : ....leaving service
  ... DemoApplication$MyController : in controller.... <= req#3
  ... DemoApplication$MyController : ....controller done!
  ... DemoApplication$MyAsyService : in service....
  ... DemoApplication$MyAsyService : ....leaving service
  

• （自动，模拟 mvc）测试（最难的部分；）：

  package com.example.demo;
  
  import static org.hamcrest.core.StringStartsWith.startsWith;
  import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
  import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
  import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.request;
  import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
  
  import java.util.UUID;
  
  import org.junit.jupiter.api.Test;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.beans.factory.annotation.Value;
  import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
  import org.springframework.mock.web.MockHttpServletRequest;
  import org.springframework.test.web.servlet.MockMvc;
  import org.springframework.test.web.servlet.MvcResult;
  import org.springframework.test.web.servlet.RequestBuilder;
  
  @WebMvcTest
  class DemoApplicationTests {
  
    @Autowired
    MockMvc mockMvc;
    @Value("${simulation.sleep.seconds}") // -> src/test/resources/application.properties
    Long simSeconds;
  
    @Test
    void testController() throws Exception {
      String uid = UUID.randomUUID().toString();
      MvcResult mvcResult = mockMvc.perform(get("/hello?req={v}", uid)) //1.
          .andExpect(request().asyncStarted()) // 2.
          .andReturn(); // 3.
  
      mockMvc.perform(asyncDispatch(mvcResult/*, (simSeconds + 1) * 1000*/)) // 4!*
          .andExpectAll( // ...
              status().isOk(),
              content().string(startsWith(uid)));
    }
    // 4*: when we take/simulate more than ~10 seconds, we have to & can re-implement/enrich:
    static RequestBuilder asyncDispatch(MvcResult mvcResult, long timeToWait) {
  
        // copied/adopted from MockMvcRequestBuilders#asyncDispatch
        mvcResult.getAsyncResult(timeToWait);
  
        return servletContext -> {
            MockHttpServletRequest request = mvcResult.getRequest();
            request.setDispatcherType(DispatcherType.ASYNC);
            request.setAsyncStarted(false);
            return request;
        };
    }
  }