一、异步执行
实现方式二种:
1. 使用异步注解@aysnc、启动类:添加@EnableAsync注解
2. JDK 8本身有一个非常好用的Future类——CompletableFuture
@AllArgsConstructorpublic class AskThread implements Runnable{private CompletableFuture<Integer> re = null;public void run() {int myRe = 0;try {myRe = re.get() * re.get();} catch (Exception e) {e.printStackTrace();}System.out.println(myRe);}public static void main(String[] args) throws InterruptedException {final CompletableFuture<Integer> future = new CompletableFuture<>();new Thread(new AskThread(future)).start();//模拟长时间的计算过程Thread.sleep(1000);//告知完成结果future.complete(60);}}
在该示例中,启动一个线程,此时AskThread对象还没有拿到它需要的数据,执行到 myRe = re.get() * re.get()会阻塞。我们用休眠1秒来模拟一个长时间的计算过程,并将计算结果告诉future执行结果,AskThread线程将会继续执行。如果您正在学习Spring Boot,那么推荐一个连载多年还在继续更新的免费教程:
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public class Calc {public static Integer calc(Integer para) {try {//模拟一个长时间的执行Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}return para * para;}public static void main(String[] args) throws ExecutionException, InterruptedException {final CompletableFuture<Void> future = CompletableFuture.supplyAsync(() -> calc(50)).thenApply((i) -> Integer.toString(i)).thenApply((str) -> "\"" + str + "\"").thenAccept(System.out::println);future.get();}}
CompletableFuture.supplyAsync方法构造一个CompletableFuture实例,在supplyAsync()方法中,它会在一个新线程中,执行传入的参数。在这里它会执行calc()方法,这个方法可能是比较慢的,但这并不影响CompletableFuture实例的构造速度,supplyAsync()会立即返回。
而返回的CompletableFuture实例就可以作为这次调用的契约,在将来任何场合,用于获得最终的计算结果。最近整理了一份最新的面试资料,里面收录了2021年各个大厂的面试题,打算跳槽的小伙伴不要错过,点击领取吧!
supplyAsync用于提供返回值的情况,CompletableFuture还有一个不需要返回值的异步调用方法runAsync(Runnable runnable),一般我们在优化Controller时,使用这个方法比较多。这两个方法如果在不指定线程池的情况下,都是在ForkJoinPool.common线程池中执行,而这个线程池中的所有线程都是Daemon(守护)线程,所以,当主线程结束时,这些线程无论执行完毕都会退出系统。
核心代码:
CompletableFuture.runAsync(() ->this.afterBetProcessor(betRequest,betDetailResult,appUser,id));异步调用使用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;}}
异步调用的方式 WebAsyncTask
@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);}}
二、增加内嵌Tomcat的最大连接数
@Configurationpublic class TomcatConfig {@Beanpublic ConfigurableServletWebServerFactory webServerFactory() {TomcatServletWebServerFactory tomcatFactory = new TomcatServletWebServerFactory();tomcatFactory.addConnectorCustomizers(new MyTomcatConnectorCustomizer());tomcatFactory.setPort(8005);tomcatFactory.setContextPath("/api-g");return tomcatFactory;}class MyTomcatConnectorCustomizer implements TomcatConnectorCustomizer {public void customize(Connector connector) {Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler();//设置最大连接数protocol.setMaxConnections(20000);//设置最大线程数protocol.setMaxThreads(2000);protocol.setConnectionTimeout(30000);}}}
三、使用@ComponentScan()定位扫包比@SpringBootApplication扫包更快
四、默认tomcat容器改为Undertow(Jboss下的服务器,Tomcat吞吐量5000,Undertow吞吐量8000)
<exclusions><exclusion><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId></exclusion></exclusions>改为:<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-undertow</artifactId></dependency>
五、使用 BufferedWriter 进行缓冲
六、Deferred方式实现异步调用
@RestControllerpublic class AsyncDeferredController {private final Logger logger = LoggerFactory.getLogger(this.getClass());private final LongTimeTask taskService;@Autowiredpublic 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(){@Overridepublic 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(){@Overridepublic void run() {logger.info(Thread.currentThread().getName() + " onCompletion");}});return deferredResult;}}
七、异步调用可以使用AsyncHandlerInterceptor进行拦截
@Componentpublic class MyAsyncHandlerInterceptor implements AsyncHandlerInterceptor {private static final Logger logger = LoggerFactory.getLogger(MyAsyncHandlerInterceptor.class);@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)throws Exception {return true;}@Overridepublic 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");}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)throws Exception {if(null != ex){System.out.println("发生异常:"+ex.getMessage());}}@Overridepublic 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");}}