spring boot--使用异步请求，提高系统的吞吐量
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 helloController() {
logger.info(Thread.currentThread().getName() + " 进入helloController方法");
Callable callable = new Callable() {
@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 worldController() {
logger.info(Thread.currentThread().getName() + " 进入helloController方法");
// 3s钟没返回，则认为超时
WebAsyncTask webAsyncTask = new WebAsyncTask<>(3000, new Callable() {
@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() {
@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 exceptionController() {
logger.info(Thread.currentThread().getName() + " 进入helloController方法");
Callable callable = new Callable() {
@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 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 executeSlowTask() {
logger.info(Thread.currentThread().getName() + "进入executeSlowTask方法");
DeferredResult 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