文章目錄

• 概述
• V1.0 默認的實現
• • Step1 搞配置類，開啟@EnableAsync
  • Step2 搞方法標記 @Async注解
  • Step3 搞調用
• Spring提供的線程池
• V2.0 實現@Async的自定義線程池
• V3.0 多個線程池處理
• • 多個線程池
  • 默認線程池
  • 驗證一把
• 源碼

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概述

Spring3開始提供了@Async注解，我們只需要在方法上標注此注解，此方法即可實現異步調用。 除此之外， 還得需要一個配置類，通過@EnableAsync 來開啟異步功能 。

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V1.0 默認的實現

Step1 搞配置類，開啟@EnableAsync

我們需要使用@EnableAsync來開啟異步任務支持。

@EnableAsync注解可以直接放在SpringBoot啟動類上，也可以單獨放在其他配置類上。

我們這里選擇單獨搞個配置類

@Configuration @EnableAsync public class ThreadPoolTaskConfig {}

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Step2 搞方法標記 @Async注解

package com.artisan.jobs;import lombok.extern.slf4j.Slf4j; import org.springframework.scheduling.annotation.Async; import org.springframework.stereotype.Component;/*** @author 小工匠* @version 1.0* @description: TODO* @date 2022/3/1 0:42* @mark: show me the code , change the world*/@Component @Slf4j public class AsyncJob {@Async public void job1() throws InterruptedException {long beginTime = System.currentTimeMillis();Thread.sleep(2000);long endTime = System.currentTimeMillis();log.info("job1 cost {} ms", endTime - beginTime);}@Async public void job2() throws InterruptedException {long beginTime = System.currentTimeMillis();Thread.sleep(2000);long endTime = System.currentTimeMillis();log.info("job2 cost {} ms", endTime - beginTime);} }

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Step3 搞調用

package com.artisan.controller;import com.artisan.jobs.AsyncJob; import lombok.extern.slf4j.Slf4j; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController;/*** @author 小工匠* @version 1.0* @description: TODO* @date 2022/3/1 0:44* @mark: show me the code , change the world*/@RestController @RequestMapping("/async") @Slf4j public class AsyncController {@Autowiredprivate AsyncJob asyncJob;@RequestMapping("/job")public String task() throws InterruptedException {long beginTime = System.currentTimeMillis();// 執行異步任務asyncJob.job1();asyncJob.job2();// 模擬業務耗時Thread.sleep(1000);long cost = System.currentTimeMillis() - beginTime;log.info("main cost {} ms", cost);return "Task Cost " + cost + " ms";} }

@Async注解在默認情況下用的是SimpleAsyncTaskExecutor線，不是真正意義上的線程池。

所以，線程名稱是 task-1 , task-2, task-3 , task-4…

2022-03-02 22:33:47.007 [http-nio-8080-exec-6] INFO com.artisan.controller.AsyncController:39 - main cost 1001 ms 2022-03-02 22:33:47.675 [http-nio-8080-exec-2] INFO com.artisan.controller.AsyncController:39 - main cost 1001 ms 2022-03-02 22:33:48.021 [task-4] INFO com.artisan.jobs.AsyncJob:35 - job2 cost 2014 ms 2022-03-02 22:33:48.021 [task-3] INFO com.artisan.jobs.AsyncJob:26 - job1 cost 2014 ms 2022-03-02 22:33:48.396 [http-nio-8080-exec-5] INFO com.artisan.controller.AsyncController:39 - main cost 1015 ms 2022-03-02 22:33:48.678 [task-6] INFO com.artisan.jobs.AsyncJob:35 - job2 cost 2004 ms 2022-03-02 22:33:48.678 [task-5] INFO com.artisan.jobs.AsyncJob:26 - job1 cost 2004 ms 2022-03-02 22:33:49.004 [http-nio-8080-exec-3] INFO com.artisan.controller.AsyncController:39 - main cost 1008 ms 2022-03-02 22:33:49.393 [task-8] INFO com.artisan.jobs.AsyncJob:35 - job2 cost 2011 ms 2022-03-02 22:33:49.393 [task-7] INFO com.artisan.jobs.AsyncJob:26 - job1 cost 2011 ms 2022-03-02 22:33:50.012 [task-9] INFO com.artisan.jobs.AsyncJob:26 - job1 cost 2015 ms 2022-03-02 22:33:50.012 [task-10] INFO com.artisan.jobs.AsyncJob:35 - job2 cost 2015 ms

可以看到，每次調用都會new一個線程。若系統中不斷的創建線程…

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Spring提供的線程池

名稱說明

SimpleAsyncTaskExecutor	這個類沒有實現異步調用，只是一個同步操作。只適用于不需要多線程的地
ConcurrentTaskExecutor	Executor的適配類，不推薦使用。如ThreadPoolTaskExecutor不滿足要求時，才用考慮使用這個類
ThreadPoolTaskScheduler	可以使用cron表達式
ThreadPoolTaskExecutor	推薦。 是對java.util.concurrent.ThreadPoolExecutor的包裝

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V2.0 實現@Async的自定義線程池

package com.artisan.config;import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.scheduling.annotation.EnableAsync; import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;import java.util.concurrent.ThreadPoolExecutor;/*** @author 小工匠* @version 1.0* @description: 使用@EnableAsync來開啟異步任務支持，@EnableAsync注解可以直接放在SpringBoot啟動類上，也可以單獨放在其他配置類上。* 我們這里選擇使用單獨的配置類AsyncConfiguration。* @date 2022/3/1 0:41* @mark: show me the code , change the world*/@Configuration @EnableAsync public class ThreadPoolTaskConfig {/*** 核心線程數（默認線程數）*/private static final int CORE_POOL_SIZE = 5;/*** 最大線程數*/private static final int MAX_POOL_SIZE = 10;/*** 允許線程空閑時間（單位：默認為秒）*/private static final int KEEP_ALIVE_TIME = 10;/*** 緩沖隊列大小*/private static final int QUEUE_CAPACITY = 200;/*** 線程池名前綴*/private static final String THREAD_NAME_PREFIX = "Async-Service-";/*** 自定義線程池** @return*/@Bean("customAsyncPoolTaskExecutor")public ThreadPoolTaskExecutor taskExecutor() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();executor.setCorePoolSize(CORE_POOL_SIZE);executor.setMaxPoolSize(MAX_POOL_SIZE);executor.setQueueCapacity(KEEP_ALIVE_TIME);executor.setKeepAliveSeconds(QUEUE_CAPACITY);executor.setThreadNamePrefix(THREAD_NAME_PREFIX);/*** 當線程池的任務緩存隊列已滿并且線程池中的線程數目達到maximumPoolSize，如果還有任務到來就會采取任務拒絕策略* 通常有以下四種策略：* ThreadPoolExecutor.AbortPolicy:丟棄任務并拋出RejectedExecutionException異常。* ThreadPoolExecutor.DiscardPolicy：丟棄任務，但是不拋出異常。* ThreadPoolExecutor.DiscardOldestPolicy：丟棄隊列最前面的任務，然后重新嘗試執行任務（重復此過程）* ThreadPoolExecutor.CallerRunsPolicy：重試添加當前的任務，自動重復調用 execute() 方法，直到成功*/executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());executor.initialize();return executor;}}

其他保持不變， 重啟測試

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V3.0 多個線程池處理

需求： 不同的業務，使用不同的線程池

多個線程池

package com.artisan.config;import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.scheduling.annotation.EnableAsync; import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;import java.util.concurrent.ThreadPoolExecutor;/*** @author 小工匠* @version 1.0* @description: 使用@EnableAsync來開啟異步任務支持，@EnableAsync注解可以直接放在SpringBoot啟動類上，也可以單獨放在其他配置類上。* 我們這里選擇使用單獨的配置類ThreadPoolTaskConfig* @date 2022/3/1 0:41* @mark: show me the code , change the world*/@Configuration @EnableAsync public class ThreadPoolTaskConfig {/*** 核心線程數（默認線程數）*/private static final int CORE_POOL_SIZE = 5;/*** 最大線程數*/private static final int MAX_POOL_SIZE = 10;/*** 允許線程空閑時間（單位：默認為秒）*/private static final int KEEP_ALIVE_TIME = 10;/*** 緩沖隊列大小*/private static final int QUEUE_CAPACITY = 200;/*** 線程池名前綴*/private static final String THREAD_NAME_PREFIX = "Biz1_Async-Service-";/*** 線程池名前綴*/private static final String THREAD_NAME_PREFIX_2= "Biz2_Async-Service-";/*** 自定義線程池** @return*/@Bean("tp1")public ThreadPoolTaskExecutor taskExecutor() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();executor.setCorePoolSize(CORE_POOL_SIZE);executor.setMaxPoolSize(MAX_POOL_SIZE);executor.setQueueCapacity(KEEP_ALIVE_TIME);executor.setKeepAliveSeconds(QUEUE_CAPACITY);executor.setThreadNamePrefix(THREAD_NAME_PREFIX);/*** 當線程池的任務緩存隊列已滿并且線程池中的線程數目達到maximumPoolSize，如果還有任務到來就會采取任務拒絕策略* 通常有以下四種策略：* ThreadPoolExecutor.AbortPolicy:丟棄任務并拋出RejectedExecutionException異常。* ThreadPoolExecutor.DiscardPolicy：丟棄任務，但是不拋出異常。* ThreadPoolExecutor.DiscardOldestPolicy：丟棄隊列最前面的任務，然后重新嘗試執行任務（重復此過程）* ThreadPoolExecutor.CallerRunsPolicy：重試添加當前的任務，自動重復調用 execute() 方法，直到成功*/executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());executor.initialize();return executor;}/*** 自定義線程池** @return*/@Bean("tp2")public ThreadPoolTaskExecutor taskExecutor2() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();executor.setCorePoolSize(CORE_POOL_SIZE);executor.setMaxPoolSize(MAX_POOL_SIZE);executor.setQueueCapacity(KEEP_ALIVE_TIME);executor.setKeepAliveSeconds(QUEUE_CAPACITY);executor.setThreadNamePrefix(THREAD_NAME_PREFIX_2);/*** 當線程池的任務緩存隊列已滿并且線程池中的線程數目達到maximumPoolSize，如果還有任務到來就會采取任務拒絕策略* 通常有以下四種策略：* ThreadPoolExecutor.AbortPolicy:丟棄任務并拋出RejectedExecutionException異常。* ThreadPoolExecutor.DiscardPolicy：丟棄任務，但是不拋出異常。* ThreadPoolExecutor.DiscardOldestPolicy：丟棄隊列最前面的任務，然后重新嘗試執行任務（重復此過程）* ThreadPoolExecutor.CallerRunsPolicy：重試添加當前的任務，自動重復調用 execute() 方法，直到成功*/executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());executor.initialize();return executor;}}

配置 多個線程池， 然后 為@Async指定線程池名字即可實現 多個線程池處理

package com.artisan.jobs;import lombok.extern.slf4j.Slf4j; import org.springframework.scheduling.annotation.Async; import org.springframework.stereotype.Component;/*** @author 小工匠* @version 1.0* @description: TODO* @date 2022/3/1 0:42* @mark: show me the code , change the world*/@Component @Slf4j public class AsyncJob {@Async("tp1")public void job1() throws InterruptedException {long beginTime = System.currentTimeMillis();Thread.sleep(2000);long endTime = System.currentTimeMillis();log.info("job1 cost {} ms", endTime - beginTime);}@Async("tp2")public void job2() throws InterruptedException {long beginTime = System.currentTimeMillis();Thread.sleep(2000);long endTime = System.currentTimeMillis();log.info("job2 cost {} ms", endTime - beginTime);}@Async()public void job3() throws InterruptedException {long beginTime = System.currentTimeMillis();Thread.sleep(2000);long endTime = System.currentTimeMillis();log.info("job3 cost {} ms", endTime - beginTime);} }

默認線程池

@Async()沒標注，用哪個？？？？？？ 當系統存在多個線程池時，我們也可以配置一個默認線程池 ，配置類讓其實現AsyncConfigurer，并重寫getAsyncExecutor()方法，指定默認線程池

package com.artisan.multi;import lombok.extern.slf4j.Slf4j; import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.scheduling.annotation.AsyncConfigurer; import org.springframework.scheduling.annotation.EnableAsync; import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;import java.util.concurrent.Executor; import java.util.concurrent.ThreadPoolExecutor;/*** @author 小工匠* @version 1.0* @mark: show me the code , change the world* <p>* 實現AsyncConfigurer，并重寫getAsyncExecutor()方法，指定默認線程池*/@Configuration @EnableAsync @Slf4j public class DefaultAsyncConfiguration implements AsyncConfigurer {/*** 核心線程數（默認線程數）*/private static final int CORE_POOL_SIZE = 2;/*** 最大線程數*/private static final int MAX_POOL_SIZE = 10;/*** 允許線程空閑時間（單位：默認為秒）*/private static final int KEEP_ALIVE_TIME = 10;/*** 緩沖隊列大小*/private static final int QUEUE_CAPACITY = 200;/*** 線程池名前綴*/private static final String THREAD_NAME_PREFIX = "Default_Async-Service-";@Bean(name = "defaultPool")public ThreadPoolTaskExecutor executor() {ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();taskExecutor.setCorePoolSize(CORE_POOL_SIZE);taskExecutor.setMaxPoolSize(MAX_POOL_SIZE);taskExecutor.setQueueCapacity(KEEP_ALIVE_TIME);taskExecutor.setKeepAliveSeconds(QUEUE_CAPACITY);taskExecutor.setThreadNamePrefix(THREAD_NAME_PREFIX);/*** 當線程池的任務緩存隊列已滿并且線程池中的線程數目達到maximumPoolSize，如果還有任務到來就會采取任務拒絕策略* 通常有以下四種策略：* ThreadPoolExecutor.AbortPolicy:丟棄任務并拋出RejectedExecutionException異常。* ThreadPoolExecutor.DiscardPolicy：丟棄任務，但是不拋出異常。* ThreadPoolExecutor.DiscardOldestPolicy：丟棄隊列最前面的任務，然后重新嘗試執行任務（重復此過程）* ThreadPoolExecutor.CallerRunsPolicy：重試添加當前的任務，自動重復調用 execute() 方法，直到成功*/taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());taskExecutor.initialize();return taskExecutor;}/*** 指定默認線程池*/@Overridepublic Executor getAsyncExecutor() {return executor();}@Overridepublic AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {return (ex, method, params) -> log.error("線程池執行任務發橫未知錯誤,執行方法：{}", method.getName(), ex);}}

驗證一把

@RestController @RequestMapping("/async") @Slf4j public class AsyncController {@Autowiredprivate AsyncJob asyncJob;@RequestMapping("/job")public String task() throws InterruptedException {long beginTime = System.currentTimeMillis();// 執行異步任務asyncJob.job1();asyncJob.job2();asyncJob.job3();// 模擬業務耗時Thread.sleep(1000);long cost = System.currentTimeMillis() - beginTime;log.info("main cost {} ms", cost);return "Task Cost " + cost + " ms";} }

完美匹配…

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源碼

https://github.com/yangshangwei/boot2

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