7 種提升 Spring Boot 吞吐量神技！
一、異步執(zhí)行
實現(xiàn)方式二種：
@aysnc、啟動類：添加@EnableAsync注解CompletableFuture@AllArgsConstructor
public?class?AskThread?implements?Runnable{
????private?CompletableFuture 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 future = new?CompletableFuture<>();
????????new?Thread(new?AskThread(future)).start();
????????//模擬長時間的計算過程
????????Thread.sleep(1000);
????????//告知完成結果
????????future.complete(60);
????}
} 在該示例中，啟動一個線程，此時AskThread對象還沒有拿到它需要的數(shù)據(jù)，執(zhí)行到 myRe = re.get() * re.get()會阻塞。我們用休眠1秒來模擬一個長時間的計算過程，并將計算結果告訴future執(zhí)行結果，AskThread線程將會繼續(xù)執(zhí)行。如果您正在學習Spring Boot，那么推薦一個連載多年還在繼續(xù)更新的免費教程：http://blog.didispace.com/spring-boot-learning-2x/
public?class?Calc?{
????public?static?Integer calc(Integer para)?{
????????try?{
????????????//模擬一個長時間的執(zhí)行
????????????Thread.sleep(1000);
????????} catch?(InterruptedException e) {
????????????e.printStackTrace();
????????}
????????return?para * para;
????}
????public?static?void?main(String[] args)?throws?ExecutionException, InterruptedException {
????????final?CompletableFuture future = CompletableFuture.supplyAsync(() -> calc(50))
????????????????.thenApply((i) -> Integer.toString(i))
????????????????.thenApply((str) -> "\""?+ str + "\"")
????????????????.thenAccept(System.out::println);
????????future.get();
????}
} CompletableFuture.supplyAsync方法構造一個CompletableFuture實例，在supplyAsync()方法中，它會在一個新線程中，執(zhí)行傳入的參數(shù)。在這里它會執(zhí)行calc()方法，這個方法可能是比較慢的，但這并不影響CompletableFuture實例的構造速度，supplyAsync()會立即返回。
而返回的CompletableFuture實例就可以作為這次調用的契約，在將來任何場合，用于獲得最終的計算結果。最近整理了一份最新的面試資料，里面收錄了2021年各個大廠的面試題，打算跳槽的小伙伴不要錯過，點擊領取吧！
supplyAsync用于提供返回值的情況，CompletableFuture還有一個不需要返回值的異步調用方法runAsync(Runnable runnable),一般我們在優(yōu)化Controller時，使用這個方法比較多。這兩個方法如果在不指定線程池的情況下，都是在ForkJoinPool.common線程池中執(zhí)行，而這個線程池中的所有線程都是Daemon（守護）線程，所以，當主線程結束時，這些線程無論執(zhí)行完畢都會退出系統(tǒng)。
核心代碼：
CompletableFuture.runAsync(()?->
???this.afterBetProcessor(betRequest,betDetailResult,appUser,id)
);異步調用使用Callable來實現(xiàn)
@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();
????}
??
????/**
?????* 異步調用restful
?????* 當controller返回值是Callable的時候，springmvc就會啟動一個線程將Callable交給TaskExecutor去處理
?????* 然后DispatcherServlet還有所有的spring攔截器都退出主線程，然后把response保持打開的狀態(tài)
?????* 當Callable執(zhí)行結束之后，springmvc就會重新啟動分配一個request請求，然后DispatcherServlet就重新
?????* 調用和處理Callable異步執(zhí)行的返回結果， 然后返回視圖
?????*
?????* @return
?????*/??
????@GetMapping("/hello")
????public?Callable<String> helloController() {
????????logger.info(Thread.currentThread().getName() + " 進入helloController方法");
????????Callable<String> callable = new?Callable<String>() {
??
????????????@Override??
????????????public?String?call() throws Exception {
????????????????logger.info(Thread.currentThread().getName() + " 進入call方法");
????????????????String?say = hello.sayHello();
????????????????logger.info(Thread.currentThread().getName() + " 從helloService方法返回");
????????????????return?say;
????????????}
????????};
????????logger.info(Thread.currentThread().getName() + " 從helloController方法返回");
????????return?callable;
????}
}異步調用的方式 WebAsyncTask
@RestController??
public?class?HelloController {
??
????private?static?final Logger logger = LoggerFactory.getLogger(HelloController.class);
??????
????@Autowired??
????private?HelloService hello;
??
????????/**
?????* 帶超時時間的異步請求 通過WebAsyncTask自定義客戶端超時間
?????*
?????* @return
?????*/??
????@GetMapping("/world")
????public?WebAsyncTask<String> worldController() {
????????logger.info(Thread.currentThread().getName() + " 進入helloController方法");
??
????????// 3s鐘沒返回，則認為超時
????????WebAsyncTask<String> webAsyncTask = new?WebAsyncTask<>(3000, new?Callable<String>() {
??
????????????@Override??
????????????public?String?call() throws Exception {
????????????????logger.info(Thread.currentThread().getName() + " 進入call方法");
????????????????String?say = hello.sayHello();
????????????????logger.info(Thread.currentThread().getName() + " 從helloService方法返回");
????????????????return?say;
????????????}
????????});
????????logger.info(Thread.currentThread().getName() + " 從helloController方法返回");
??
????????webAsyncTask.onCompletion(new?Runnable() {
??
????????????@Override??
????????????public?void?run() {
????????????????logger.info(Thread.currentThread().getName() + " 執(zhí)行完畢");
????????????}
????????});
??
????????webAsyncTask.onTimeout(new?Callable<String>() {
??
????????????@Override??
????????????public?String?call() throws Exception {
????????????????logger.info(Thread.currentThread().getName() + " onTimeout");
????????????????// 超時的時候，直接拋異常，讓外層統(tǒng)一處理超時異常
????????????????throw?new?TimeoutException("調用超時");
????????????}
????????});
????????return?webAsyncTask;
????}
??
????/**
?????* 異步調用，異常處理，詳細的處理流程見MyExceptionHandler類
?????*
?????* @return
?????*/??
????@GetMapping("/exception")
????public?WebAsyncTask<String> exceptionController() {
????????logger.info(Thread.currentThread().getName() + " 進入helloController方法");
????????Callable<String> callable = new?Callable<String>() {
??
????????????@Override??
????????????public?String?call() throws Exception {
????????????????logger.info(Thread.currentThread().getName() + " 進入call方法");
????????????????throw?new?TimeoutException("調用超時!");
????????????}
????????};
????????logger.info(Thread.currentThread().getName() + " 從helloController方法返回");
????????return?new?WebAsyncTask<>(20000, callable);
????}
??
}二、增加內嵌Tomcat的最大連接數(shù)
@Configuration
public?class?TomcatConfig?{
????@Bean
????public?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();
????????????//設置最大連接數(shù)
????????????protocol.setMaxConnections(20000);
????????????//設置最大線程數(shù)
????????????protocol.setMaxThreads(2000);
????????????protocol.setConnectionTimeout(30000);
????????}
????}
}三、使用@ComponentScan()定位掃包比@SpringBootApplication掃包更快
四、默認tomcat容器改為Undertow（Jboss下的服務器，Tomcat吞吐量5000，Undertow吞吐量8000）
<exclusions>
??<exclusion>
?????<groupId>org.springframework.bootgroupId>
?????<artifactId>spring-boot-starter-tomcatartifactId>
??exclusion>
exclusions>改為:
<dependency>
??<groupId>org.springframework.bootgroupId>
??<artifactId>spring-boot-starter-undertowartifactId>
dependency>五、使用 BufferedWriter 進行緩沖
六、Deferred方式實現(xiàn)異步調用
@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() + "進入executeSlowTask方法");
????????DeferredResult deferredResult = new?DeferredResult<>();
????????// 調用長時間執(zhí)行任務
????????taskService.execute(deferredResult);
????????// 當長時間任務中使用deferred.setResult("world");這個方法時，會從長時間任務中返回，繼續(xù)controller里面的流程
????????logger.info(Thread.currentThread().getName() + "從executeSlowTask方法返回");
????????// 超時的回調方法
????????deferredResult.onTimeout(new?Runnable(){
??
???@Override
???public?void?run()?{
????logger.info(Thread.currentThread().getName() + " onTimeout");
????// 返回超時信息
????deferredResult.setErrorResult("time out!");
???}
??});
????????
????????// 處理完成的回調方法，無論是超時還是處理成功，都會進入這個回調方法
????????deferredResult.onCompletion(new?Runnable(){
??
???@Override
???public?void?run()?{
????logger.info(Thread.currentThread().getName() + " onCompletion");
???}
??});
????????
????????return?deferredResult;
????}
} 七、異步調用可以使用AsyncHandlerInterceptor進行攔截
@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()+ "服務調用完成，返回結果給客戶端");
?}
?
?@Override
?public?void?afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
???throws?Exception {
??if(null?!= ex){
???System.out.println("發(fā)生異常:"+ex.getMessage());
??}
?}
?
?@Override
?public?void?afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler)
???throws?Exception {
??
??// 攔截之后，重新寫回數(shù)據(jù)，將原來的hello world換成如下字符串
??String resp = "my name is chhliu!";
??response.setContentLength(resp.length());
??response.getOutputStream().write(resp.getBytes());
??
??logger.info(Thread.currentThread().getName() + " 進入afterConcurrentHandlingStarted方法");
?}
?
}參考
https://my.oschina.net/u/3768341/blog/3001731
https://blog.csdn.net/liuchuanhong1/article/details/78744138
來源：https://xhcom.blog.csdn.net/article/details/88046026
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