1. 普通線程實(shí)現(xiàn)異步，但頻繁創(chuàng)建、銷毀線程比較耗資源，所以一般交給線程池執(zhí)行

   //創(chuàng)建需要異步執(zhí)行的邏輯
   public class AsyncThread implements Runnable{
       @Override
       public void run() {
           System.out.println("異步線程開始");
           long start = System.currentTimeMillis();
           try {
               TimeUnit.SECONDS.sleep(3);
           } catch (InterruptedException e) {
               throw new RuntimeException(e);
           }
           long end = System.currentTimeMillis();
           System.out.println("異步線程：" + Thread.currentThread().getName() + "結(jié)束，耗時(shí)：" + (end - start));
       }
   }
   
   //在業(yè)務(wù)中進(jìn)行調(diào)用
   @GetMapping("/thread")
   public String asyncThread(){
       ThreadPoolExecutor threadPool = new ThreadPoolExecutor(3, 3, 5, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(10), new ThreadPoolExecutor.AbortPolicy());
       long start = System.currentTimeMillis();
       //自己的業(yè)務(wù)代碼。。。
       AsyncThread asyncThread = new AsyncThread();
       threadPool.execute(asyncThread);
       long end = System.currentTimeMillis();
       return "返回,耗時(shí):" + (end - start);
   }
   

   結(jié)果：

2. Future異步

   和普通線程實(shí)現(xiàn)異步區(qū)別不大，只是使用Future是要獲取執(zhí)行后的返回值

   //創(chuàng)建具有返回值的任務(wù)
   public class CallableThread implements Callable {
       @Override
       public String call() throws Exception {
           long start = System.currentTimeMillis();
           StopWatch stopWatch = new StopWatch();
           stopWatch.start();
           System.out.println("callable任務(wù)開始執(zhí)行:" + start);
           TimeUnit.SECONDS.sleep(2);
           System.out.println();
           stopWatch.stop();
           System.out.println("stopWatch.prettyPrint------");
           System.out.println(stopWatch.prettyPrint());
           System.out.println("stopWatch.shortSummary------");
           System.out.println(stopWatch.shortSummary());
           System.out.println("stopWatch.getTotalTimeMillis------");
           System.out.println(stopWatch.getTotalTimeMillis());
           return "call執(zhí)行結(jié)束 ";
       }
   }
   
   //在業(yè)務(wù)中進(jìn)行調(diào)用
   public String threadFuture(){
       ThreadPoolExecutor threadPool = new ThreadPoolExecutor(3, 3, 5, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(10), new ThreadPoolExecutor.AbortPolicy());
       long start = System.currentTimeMillis();
       CallableThread callableThread = new CallableThread();
       Future<String> submit = threadPool.submit(callableThread);
       try {
           //在獲取返回值時(shí)會(huì)阻塞主線程
           String s = "";
           s = submit.get();
           System.out.println(s);
       } catch (Exception e) {
           System.out.println("線程運(yùn)行發(fā)生錯(cuò)誤" + e.getMessage());
           throw new RuntimeException(e);
       }
       long end = System.currentTimeMillis();
       return "接口返回,耗時(shí):" + (end - start);
   }
   

   結(jié)果：

3. Spring的@Async異步

   • 使用@Async注解實(shí)現(xiàn)異步的前提是需要在啟動(dòng)類上標(biāo)注@EnableAsync來開啟異步配置

   • 配置線程池（@Async默認(rèn)情況下用的是SimpleAsyncTaskExecutor線程池，該線程池不是真正意義上的線程池，使用此線程池?zé)o法實(shí)現(xiàn)線程重用，每次調(diào)用都會(huì)新建一條線程。若系統(tǒng)中不斷的創(chuàng)建線程，最終會(huì)導(dǎo)致系統(tǒng)占用內(nèi)存過高，引發(fā)OutOfMemoryError錯(cuò)誤）

     /**
      * 線程池配置，可以配置多個(gè)線程池
      * @Async注解，默認(rèn)使用系統(tǒng)自定義線程池，可在項(xiàng)目中設(shè)置多個(gè)線程池，在異步調(diào)用的時(shí)候，指明需要調(diào)用的線程池名稱
      * 比如：@Async("線程池1")
      */
     @Configuration
     public class ExecutorConfig {
         /**
          * 自定義線程池
          */
         @Bean("myExecutor")
         public Executor taskExecutor(){
             System.out.println("系統(tǒng)最大線程數(shù):" + Runtime.getRuntime().availableProcessors());
             ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();
             threadPoolTaskExecutor.setCorePoolSize(8);//核心線程數(shù)
             threadPoolTaskExecutor.setMaxPoolSize(16);//最大線程數(shù)
             threadPoolTaskExecutor.setQueueCapacity(1000);//配置隊(duì)列容量
             threadPoolTaskExecutor.setKeepAliveSeconds(60);//空閑線程存活時(shí)間
             threadPoolTaskExecutor.setThreadNamePrefix("myExecutor-");//線程名字前綴
             return threadPoolTaskExecutor;
         }
     }
     

   • 編寫異步方法的邏輯，異步方法所在的類需要被Spring管理

     @Service
     public class AsyncServiceImpl implements AsyncService {
         @Override
         @Async("myExecutor")
         public void sendMsg() {
             System.out.println("進(jìn)入異步方法");
             System.out.println("當(dāng)前線程名稱：" + Thread.currentThread().getName());
             try {
                 TimeUnit.SECONDS.sleep(2);
             } catch (InterruptedException e) {
                 throw new RuntimeException(e);
             }
             System.out.println("異步方法執(zhí)行完成");
         }
     
         /**
          * 具有返回值的異步方法，返回類型為Future,返回時(shí)new 一個(gè)AsyncResult對(duì)象，其中參數(shù)為返回的內(nèi)容
          * @return
          */
         @Override
         @Async("myExecutor")
         public Future<String> sendMsgFuture() {
             System.out.println("進(jìn)入future異步方法");
             try {
                 TimeUnit.SECONDS.sleep(2);
             } catch (InterruptedException e) {
                 throw new RuntimeException(e);
             }
             return new AsyncResult<>("future異步方法執(zhí)行完成");
         }
     }
     

   • 在業(yè)務(wù)邏輯中調(diào)用

     @GetMapping("/asyncMethod")
     public String asyncMethod(){
         System.out.println("aaa");
         System.out.println("調(diào)用異步方法");
         asyncService.sendMsg();
         System.out.println("bbb");
         return "asyncMethod方法返回";
     }
     

     調(diào)用沒有返回值的異步方法結(jié)果：

     @GetMapping("/asyncFutureMethod")
     public String asyncFutureMethod(){
         System.out.println("aaa");
         Future<String> stringFuture = asyncService.sendMsgFuture();
         System.out.println("bbb");
         try {
         System.out.println(stringFuture.get());//get方法會(huì)阻塞主線程
         } catch (Exception e) {
         throw new RuntimeException(e);
         }
         return "asyncfutureMethod方法返回";
     }
     

     調(diào)用有返回值的異步方法結(jié)果：

4. Spring的ApplicationEvent事件實(shí)現(xiàn)異步

   • 定義事件，繼承ApplicationEvent類

     public class MessageEvent extends ApplicationEvent {
         @Getter
         private String message;
     
         public MessageEvent(Object source, String message) {
             super(source);
             this.message = message;
         }
     }
     

   • 定義監(jiān)聽器（需要被Spring管理）

     使用@EventListener注解寫在方法上定義一個(gè)監(jiān)聽器，即事件被觸發(fā)時(shí)執(zhí)行的方法(默認(rèn)是同步執(zhí)行，可以使用@Async注解標(biāo)注為異步執(zhí)行)，支持多個(gè)監(jiān)聽器監(jiān)聽同一個(gè)事件。

     @Component
     public class MessageEventHandler {
     
         //@Async
         @EventListener
         public void handleLoginEvent(LoginEvent event){
             System.out.println("接受到LoginEvent事件");
             try {
                 TimeUnit.SECONDS.sleep(2);
             } catch (InterruptedException e) {
                 throw new RuntimeException(e);
             }
             System.out.println(event.getUsername());
             System.out.println("LoginEvent事件處理完成");
         }
     
         //@Async
         @EventListener
         public void handleMessageEvent(MessageEvent event){
             System.out.println("接受到MessageEvent事件");
             try {
                 TimeUnit.SECONDS.sleep(2);
             } catch (InterruptedException e) {
                 throw new RuntimeException(e);
             }
             System.out.println(event.getMessage());
             System.out.println("MessageEvent事件處理完成");
         }
     }
     

   • 定義事件發(fā)布者(觸發(fā)事件的)（需要被Spring管理）

     實(shí)現(xiàn)ApplicationEventPublisherAware接口

     @Component
     public class EventPublisher implements ApplicationEventPublisherAware {
         private ApplicationEventPublisher publisher;
     
         @Override
         public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
             this.publisher = applicationEventPublisher;
         }
     
         public void publish(ApplicationEvent event){
             if (event instanceof MessageEvent){
                 System.out.println("開始發(fā)布MessageEvent事件:" + ((MessageEvent) event).getMessage());
             } else if (event instanceof LoginEvent) {
                 System.out.println("開始發(fā)布LoginEvent事件:" + ((LoginEvent) event).getUsername());
             }
             //發(fā)布事件
             publisher.publishEvent(event);
             System.out.println("事件發(fā)布結(jié)束");
         }
     
     }
     

   • 業(yè)務(wù)代碼執(zhí)行時(shí)觸發(fā)事件

     @GetMapping("/pubEvent")
     public String publishEvent(){
         System.out.println("業(yè)務(wù)邏輯開始");
         eventPublisher.publish(new MessageEvent(this,"testEvent"));
         System.out.println("業(yè)務(wù)邏輯結(jié)束");
         return "發(fā)布成功";
     }
     

     執(zhí)行結(jié)果：

     由控制臺(tái)打印可以發(fā)現(xiàn)現(xiàn)在事件監(jiān)聽器方法的執(zhí)行是同步的，如果需要異步執(zhí)行，在監(jiān)聽器方法上加個(gè)@Async注解即可，但使用Async注解的前提是在啟動(dòng)類上標(biāo)注@EnableAsync注解來開啟異步配置

     使用@Async注解后執(zhí)行結(jié)果：

     可以看到監(jiān)聽器中的打印在最后了，證明是異步執(zhí)行的文章來源地址http://www.zghlxwxcb.cn/news/detail-759990.html

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