Springboot使用异步请求提高系统的吞吐量详解

@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;
	}
}

@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);
	}
}

@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();
		}
	}
}

@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;
    }
}

@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");
	}
}