在SpringBoot怎麼優雅的使用多線程-java教程-PHP中文網

快速使用

SpringBoot應用程式中需要新增@EnableAsync註解，來開啟非同步調用，一般也會配置一個執行緒池，非同步的方法交給特定的執行緒池完成，如下：

@Configuration
@EnableAsync
public class AsyncConfiguration {
 
    @Bean("doSomethingExecutor")
    public Executor doSomethingExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        // 核心线程数：线程池创建时候初始化的线程数
        executor.setCorePoolSize(10);
        // 最大线程数：线程池最大的线程数，只有在缓冲队列满了之后才会申请超过核心线程数的线程
        executor.setMaxPoolSize(20);
        // 缓冲队列：用来缓冲执行任务的队列
        executor.setQueueCapacity(500);
        // 允许线程的空闲时间60秒：当超过了核心线程之外的线程在空闲时间到达之后会被销毁
        executor.setKeepAliveSeconds(60);
        // 线程池名的前缀：设置好了之后可以方便我们定位处理任务所在的线程池
        executor.setThreadNamePrefix("do-something-");
        // 缓冲队列满了之后的拒绝策略：由调用线程处理（一般是主线程）
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
        executor.initialize();
        return executor;
    }
 
}

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使用的方式非常簡單，在需要非同步的方法上加上@Async註解

@RestController
public class AsyncController {
 
    @Autowired
    private AsyncService asyncService;
 
    @GetMapping("/open/something")
    public String something() {
        int count = 10;
        for (int i = 0; i < count; i++) {
            asyncService.doSomething("index = " + i);
        }
        return "success";
    }
}
 
 
@Slf4j
@Service
public class AsyncService {
 
    // 指定使用beanname为doSomethingExecutor的线程池
    @Async("doSomethingExecutor")
    public String doSomething(String message) {
        log.info("do something, message={}", message);
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            log.error("do something error: ", e);
        }
        return message;
    }
}

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存取：127.0.0.1:8080/open/something，日誌如下

#2023 -02-06 23:42:42.486 INFO 21168 --- [io-8200-exec-17] x.g.b.system.controller.AsyncController : do something end, time 8 milliseconds##2023838-0283:48 INFO 21168 --- [ do-something-1] x.gits.boot.system.service.AsyncService : do something, message=index = 0
2023-02-06 23:42:42.488 INFO 2118 --- [ do-something-5] x.gits.boot.system.service.AsyncService : do something, message=index = 4
2023-02-06 23:42:42.488 INFO 21168 --- [ do-something- 4] x.gits.boot.system.service.AsyncService : do something, message=index = 3
2023-02-06 23:42:42.488 INFO 21168 --- [ do-something-6] x.gits .boot.system.service.AsyncService : do something, message=index = 5
2023-02-06 23:42:42.488 INFO 21168 --- [ do-something-9] x.gits.boot.system. service.AsyncService : do something, message=index = 8
2023-02-06 23:42:42.488 INFO 21168 --- [ do-something-8] x.gits.boot.Service.service.Asydo system.service.Asydonc 系統. something, message=index = 7
2023-02-06 23:42:42.488 INFO 21168 --- [do-something-10] x.gits.boot.system.service.AsyncService : do something, message=index.AsyncService : do something, message=index = 9
2023-02-06 23:42:42.488 INFO 21168 --- [ do-something-7] x.gits.boot.system.service.AsyncService : do something, message=index = 6
2023-02-06 23:42:42.488 INFO 21168 --- [ do-something-2] x.gits.boot.system.service.AsyncService : do something, message=index = 1
#2023-02-06 23:42:42.488 INFO 21168 --- [ do-something-3] x.gits.boot.system.service.AsyncService : do something, message=index = 2

#由此可見已經可見已經可見已經可見達到非同步執行的效果了，並且使用到了咱們配置的線程池。

取得非同步方法傳回值

當非同步方法有回傳值時，如何取得非同步方法執行的回傳結果呢？這時需要非同步呼叫的方法帶有傳回值CompletableFuture。

CompletableFuture是對Feature的增強，Feature只能處理簡單的非同步任務，而CompletableFuture可以將多個非同步任務進行複雜的組合。如下：

@RestController
public class AsyncController {
 
    @Autowired
    private AsyncService asyncService;
 
    @SneakyThrows
    @ApiOperation("异步 有返回值")
    @GetMapping("/open/somethings")
    public String somethings() {
        CompletableFuture<String> createOrder = asyncService.doSomething1("create order");
        CompletableFuture<String> reduceAccount = asyncService.doSomething2("reduce account");
        CompletableFuture<String> saveLog = asyncService.doSomething3("save log");
 
        // 等待所有任务都执行完
        CompletableFuture.allOf(createOrder, reduceAccount, saveLog).join();
        // 获取每个任务的返回结果
        String result = createOrder.get() + reduceAccount.get() + saveLog.get();
        return result;
    }
}
 
 
@Slf4j
@Service
public class AsyncService {
 
    @Async("doSomethingExecutor")
    public CompletableFuture<String> doSomething1(String message) throws InterruptedException {
        log.info("do something1: {}", message);
        Thread.sleep(1000);
        return CompletableFuture.completedFuture("do something1: " + message);
    }
 
    @Async("doSomethingExecutor")
    public CompletableFuture<String> doSomething2(String message) throws InterruptedException {
        log.info("do something2: {}", message);
        Thread.sleep(1000);
        return CompletableFuture.completedFuture("; do something2: " + message);
    }
 
    @Async("doSomethingExecutor")
    public CompletableFuture<String> doSomething3(String message) throws InterruptedException {
        log.info("do something3: {}", message);
        Thread.sleep(1000);
        return CompletableFuture.completedFuture("; do something3: " + message);
    }
}

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存取介面

C:\Users\Administrator>curl -X GET "http://localhost:8080/open/something" -H "accept: * /*"
do something1: create order;
do something2: reduce account;
do something3: save log

控制台上關鍵日誌如下：

2023-02-06 00:27:42.238 INFO 5672 --- [ do-something-3] x.gits.boot.system.service.AsyncService : do something3: save log
#2023-02- 06 00:27:42.238 INFO 5672 --- [ do-something-2] x.gits.boot.system.service.AsyncService : do something2: reduce account
2023-02-06 00:27: reduce account
2023-02-06 00:27: reduce account
2023-02-06 00:27:402. --- [ do-something-1] x.gits.boot.system.service.AsyncService : do something1: create order

注意事項

@Async註解會在以下幾個場景失效，也就是說明明使用了@Async註解，但就沒有走多執行緒。