spring boot--使用异步请求，提高系统的吞吐量

ゝ一纸荒年。 2023-10-23 00:42 106阅读 0赞

一、使用Callable来实现

@RestController
    public class HelloController {
     
    	private static final Logger logger = LoggerFactory.getLogger(HelloController.class);
    	
    	@Autowired
    	private HelloService hello;
     
    	@GetMapping("/helloworld")
    	public String helloWorldController() {
    		return hello.sayHello();
    	}
     
    	/**
    	 * 异步调用restful
    	 * 当controller返回值是Callable的时候，springmvc就会启动一个线程将Callable交给TaskExecutor去处理
    	 * 然后DispatcherServlet还有所有的spring拦截器都退出主线程，然后把response保持打开的状态
    	 * 当Callable执行结束之后，springmvc就会重新启动分配一个request请求，然后DispatcherServlet就重新
    	 * 调用和处理Callable异步执行的返回结果， 然后返回视图
    	 * 
    	 * @return
    	 */
    	@GetMapping("/hello")
    	public Callable<String> helloController() {
    		logger.info(Thread.currentThread().getName() + " 进入helloController方法");
    		Callable<String> callable = new Callable<String>() {
     
    			@Override
    			public String call() throws Exception {
    				logger.info(Thread.currentThread().getName() + " 进入call方法");
    				String say = hello.sayHello();
    				logger.info(Thread.currentThread().getName() + " 从helloService方法返回");
    				return say;
    			}
    		};
    		logger.info(Thread.currentThread().getName() + " 从helloController方法返回");
    		return callable;
    	}
    }

使用Callable异步请求的结果：

2017-12-07 18:11:55.671  INFO 6196 --- [nio-8060-exec-1] c.travelsky.controller.HelloController   : http-nio-8060-exec-1 进入helloController方法
    2017-12-07 18:11:55.672  INFO 6196 --- [nio-8060-exec-1] c.travelsky.controller.HelloController   : http-nio-8060-exec-1 从helloController方法返回
    2017-12-07 18:11:55.676  INFO 6196 --- [nio-8060-exec-1] c.t.i.MyAsyncHandlerInterceptor          : http-nio-8060-exec-1 进入afterConcurrentHandlingStarted方法
    2017-12-07 18:11:55.676  INFO 6196 --- [      MvcAsync1] c.travelsky.controller.HelloController   : MvcAsync1 进入call方法
    2017-12-07 18:11:55.676  INFO 6196 --- [      MvcAsync1] com.travelsky.service.HelloService       : MvcAsync1 进入sayHello方法!
    2017-12-07 18:11:57.677  INFO 6196 --- [      MvcAsync1] c.travelsky.controller.HelloController   : MvcAsync1 从helloService方法返回
    2017-12-07 18:11:57.721  INFO 6196 --- [nio-8060-exec-2] c.t.i.MyAsyncHandlerInterceptor          : http-nio-8060-exec-2服务调用完成，返回结果给客户端

2.通过WebAsyncTask，也能实现异步调用

@RestController
    public class HelloController {
     
    	private static final Logger logger = LoggerFactory.getLogger(HelloController.class);
    	
    	@Autowired
    	private HelloService hello;
     
    		/**
    	 * 带超时时间的异步请求 通过WebAsyncTask自定义客户端超时间
    	 * 
    	 * @return
    	 */
    	@GetMapping("/world")
    	public WebAsyncTask<String> worldController() {
    		logger.info(Thread.currentThread().getName() + " 进入helloController方法");
     
    		// 3s钟没返回，则认为超时
    		WebAsyncTask<String> webAsyncTask = new WebAsyncTask<>(3000, new Callable<String>() {
     
    			@Override
    			public String call() throws Exception {
    				logger.info(Thread.currentThread().getName() + " 进入call方法");
    				String say = hello.sayHello();
    				logger.info(Thread.currentThread().getName() + " 从helloService方法返回");
    				return say;
    			}
    		});
    		logger.info(Thread.currentThread().getName() + " 从helloController方法返回");
     
    		webAsyncTask.onCompletion(new Runnable() {
     
    			@Override
    			public void run() {
    				logger.info(Thread.currentThread().getName() + " 执行完毕");
    			}
    		});
     
    		webAsyncTask.onTimeout(new Callable<String>() {
     
    			@Override
    			public String call() throws Exception {
    				logger.info(Thread.currentThread().getName() + " onTimeout");
    				// 超时的时候，直接抛异常，让外层统一处理超时异常
    				throw new TimeoutException("调用超时");
    			}
    		});
    		return webAsyncTask;
    	}
     
    	/**
    	 * 异步调用，异常处理，详细的处理流程见MyExceptionHandler类
    	 * 
    	 * @return
    	 */
    	@GetMapping("/exception")
    	public WebAsyncTask<String> exceptionController() {
    		logger.info(Thread.currentThread().getName() + " 进入helloController方法");
    		Callable<String> callable = new Callable<String>() {
     
    			@Override
    			public String call() throws Exception {
    				logger.info(Thread.currentThread().getName() + " 进入call方法");
    				throw new TimeoutException("调用超时!");
    			}
    		};
    		logger.info(Thread.currentThread().getName() + " 从helloController方法返回");
    		return new WebAsyncTask<>(20000, callable);
    	}
     
    }

运行结果如下：

2017-12-07 19:10:26.582  INFO 6196 --- [nio-8060-exec-4] c.travelsky.controller.HelloController   : http-nio-8060-exec-4 进入helloController方法
    2017-12-07 19:10:26.585  INFO 6196 --- [nio-8060-exec-4] c.travelsky.controller.HelloController   : http-nio-8060-exec-4 从helloController方法返回
    2017-12-07 19:10:26.589  INFO 6196 --- [nio-8060-exec-4] c.t.i.MyAsyncHandlerInterceptor          : http-nio-8060-exec-4 进入afterConcurrentHandlingStarted方法
    2017-12-07 19:10:26.591  INFO 6196 --- [      MvcAsync2] c.travelsky.controller.HelloController   : MvcAsync2 进入call方法
    2017-12-07 19:10:26.591  INFO 6196 --- [      MvcAsync2] com.travelsky.service.HelloService       : MvcAsync2 进入sayHello方法!
    2017-12-07 19:10:28.591  INFO 6196 --- [      MvcAsync2] c.travelsky.controller.HelloController   : MvcAsync2 从helloService方法返回
    2017-12-07 19:10:28.600  INFO 6196 --- [nio-8060-exec-5] c.t.i.MyAsyncHandlerInterceptor          : http-nio-8060-exec-5服务调用完成，返回结果给客户端
    2017-12-07 19:10:28.601  INFO 6196 --- [nio-8060-exec-5] c.travelsky.controller.HelloController   : http-nio-8060-exec-5 执行完毕

这种方式和上面的callable方式最大的区别就是，WebAsyncTask支持超时，并且还提供了两个回调函数，分别是onCompletion和onTimeout，顾名思义，这两个回调函数分别在执行完成和超时的时候回调。

3、Deferred方式实现异步调用

在我们是生产中，往往会遇到这样的情景，controller中调用的方法很多都是和第三方有关的，例如JMS，定时任务，队列等，拿JMS来说，比如controller里面的服务需要从JMS中拿到返回值，才能给客户端返回，而从JMS拿值这个过程也是异步的，这个时候，我们就可以通过Deferred来实现整个的异步调用。

首先，我们来模拟一个长时间调用的任务，代码如下：

@Component
    public class LongTimeTask {
    	private final Logger logger = LoggerFactory.getLogger(this.getClass());
    	@Async
    	public void execute(DeferredResult<String> deferred){
    		logger.info(Thread.currentThread().getName() + "进入 taskService 的 execute方法");
    		try {
    			// 模拟长时间任务调用，睡眠2s
    			TimeUnit.SECONDS.sleep(2);
    			// 2s后给Deferred发送成功消息，告诉Deferred，我这边已经处理完了，可以返回给客户端了
    			deferred.setResult("world");
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    	}
    }

接着，我们就来实现异步调用，controller如下：

@RestController
    public class AsyncDeferredController {
        private final Logger logger = LoggerFactory.getLogger(this.getClass());
        private final LongTimeTask taskService;
        
        @Autowired
        public AsyncDeferredController(LongTimeTask taskService) {
            this.taskService = taskService;
        }
        
        @GetMapping("/deferred")
        public DeferredResult<String> executeSlowTask() {
            logger.info(Thread.currentThread().getName() + "进入executeSlowTask方法");
            DeferredResult<String> deferredResult = new DeferredResult<>();
            // 调用长时间执行任务
            taskService.execute(deferredResult);
            // 当长时间任务中使用deferred.setResult("world");这个方法时，会从长时间任务中返回，继续controller里面的流程
            logger.info(Thread.currentThread().getName() + "从executeSlowTask方法返回");
            // 超时的回调方法
            deferredResult.onTimeout(new Runnable(){
    		
    			@Override
    			public void run() {
    				logger.info(Thread.currentThread().getName() + " onTimeout");
    				// 返回超时信息
    				deferredResult.setErrorResult("time out!");
    			}
    		});
            
            // 处理完成的回调方法，无论是超时还是处理成功，都会进入这个回调方法
            deferredResult.onCompletion(new Runnable(){
    		
    			@Override
    			public void run() {
    				logger.info(Thread.currentThread().getName() + " onCompletion");
    			}
    		});
            
            return deferredResult;
        }
    }

执行结果如下：

2017-12-07 19:25:40.192  INFO 6196 --- [nio-8060-exec-7] c.t.controller.AsyncDeferredController   : http-nio-8060-exec-7进入executeSlowTask方法
    2017-12-07 19:25:40.193  INFO 6196 --- [nio-8060-exec-7] .s.a.AnnotationAsyncExecutionInterceptor : No TaskExecutor bean found for async processing
    2017-12-07 19:25:40.194  INFO 6196 --- [nio-8060-exec-7] c.t.controller.AsyncDeferredController   : http-nio-8060-exec-7从executeSlowTask方法返回
    2017-12-07 19:25:40.198  INFO 6196 --- [nio-8060-exec-7] c.t.i.MyAsyncHandlerInterceptor          : http-nio-8060-exec-7 进入afterConcurrentHandlingStarted方法
    2017-12-07 19:25:40.202  INFO 6196 --- [cTaskExecutor-1] com.travelsky.controller.LongTimeTask    : SimpleAsyncTaskExecutor-1进入 taskService 的 execute方法
    2017-12-07 19:25:42.212  INFO 6196 --- [nio-8060-exec-8] c.t.i.MyAsyncHandlerInterceptor          : http-nio-8060-exec-8服务调用完成，返回结果给客户端
    2017-12-07 19:25:42.213  INFO 6196 --- [nio-8060-exec-8] c.t.controller.AsyncDeferredController   : http-nio-8060-exec-8 onCompletion

从上面的执行结果不难看出，容器线程会立刻返回，应用程序使用线程池里面的cTaskExecutor-1线程来完成长时间任务的调用，当调用完成后，容器又启了一个连接线程，来返回最终的执行结果。

这种异步调用，在容器线程资源非常宝贵的时候，能够大大的提高整个系统的吞吐量。

ps：异步调用可以使用AsyncHandlerInterceptor进行拦截，使用示例如下：

@Component
    public class MyAsyncHandlerInterceptor implements AsyncHandlerInterceptor {
    	
    	private static final Logger logger = LoggerFactory.getLogger(MyAsyncHandlerInterceptor.class);
     
    	@Override
    	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
    			throws Exception {
    		return true;
    	}
     
    	@Override
    	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
    			ModelAndView modelAndView) throws Exception {
    //		HandlerMethod handlerMethod = (HandlerMethod) handler;
    		logger.info(Thread.currentThread().getName()+ "服务调用完成，返回结果给客户端");
    	}
     
    	@Override
    	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
    			throws Exception {
    		if(null != ex){
    			System.out.println("发生异常:"+ex.getMessage());
    		}
    	}
     
    	@Override
    	public void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler)
    			throws Exception {
    		
    		// 拦截之后，重新写回数据，将原来的hello world换成如下字符串
    		String resp = "my name is chhliu!";
    		response.setContentLength(resp.length());
    		response.getOutputStream().write(resp.getBytes());
    		
    		logger.info(Thread.currentThread().getName() + " 进入afterConcurrentHandlingStarted方法");
    	}
     
    }

[ 原文][Link 1]

[Link 1]: https://blog.csdn.net/luckykapok918/article/details/79105698