springboot之线程池ThreadPoolTaskExecutor以及@Async异步注解

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前言

最近项目当中有需求,要进行异步的处理,需要使用到线程池,很久没有使用到线程池了,一来是做JAVAweb开发基本上很少用到异步处理,二来是发现有的老项目里面,线程和线程池的使用比较混乱,有好几个线程池,有的线程池是通过spring管理的,有的是自己创建的,然后有的地方是直接创建的线程。所以这里记录下自己在项目当中如何优雅的使用线程池!避免项目当中到处都是线程池!!!

SpringBoot整合ThreadPoolTaskExecutor线程池

ThreadPoolExecutor:这个是JAVA自己实现的线程池执行类,基本上创建线程池都是通过这个类进行的创建!
ThreadPoolTaskExecutor :这个是springboot基于ThreadPoolExecutor实现的一个线程池执行类。

In the absence of an Executor bean in the context, Spring Boot auto-configures a ThreadPoolTaskExecutor with sensible defaults that can be automatically associated to asynchronous task execution (@EnableAsync) and Spring MVC asynchronous request processing.

在springboot当中,根据 官方文档的说明,如果没有配置线程池的话,springboot会自动配置一个ThreadPoolTaskExecutor 线程池到bean当中,我们只需要按照他的方式调用就可以了!!!

使用springboot默认的线程池

既然springboot有默认的线程池,说明我们可以很简单的进行调用

方式一:通过@Async注解调用

第一步:在Application启动类上面加上@EnableAsync

@SpringBootApplication
@EnableAsync
public class ThreadpoolApplication {
    public static void main(String[] args) {
        SpringApplication.run(ThreadpoolApplication.class, args);
    }
}

第二步:在需要异步执行的方法上加上@Async注解

@Service
public class AsyncTest {
    protected final Logger logger = LoggerFactory.getLogger(this.getClass());
    @Async
    public void hello(String name){
    	//这里使用logger 方便查看执行的线程是什么
        logger.info("异步线程启动 started."+name);  
    }
}

第三步:测试类进行测试验证

    @Autowired
    AsyncTest asyncTest;
    @Test
    void contextLoads() throws InterruptedException {
        asyncTest.hello("afsasfasf");
        //一定要休眠 不然主线程关闭了,子线程还没有启动
        Thread.sleep(1000);
    }

查看打印的日志:

INFO 2276 --- [ main] c.h.s.t.t.ThreadpoolApplicationTests : Started ThreadpoolApplicationTests in 3.003 seconds (JVM running for 5.342)
INFO 2276 --- [ task-1] c.h.s.threadpool.threadpool.AsyncTest : 异步线程启动 started.afsasfasf

可以清楚的看到新开了一个task-1的线程执行任务。验证成功!!!

方式二:直接调用ThreadPoolTaskExecutor

修改上面测试类,直接注入ThreadPoolTaskExecutor

@SpringBootTest
class ThreadPoolApplicationTests {
    protected final Logger logger = LoggerFactory.getLogger(this.getClass());

    @Autowired
    AsyncTest asyncTest;
    @Autowired
    ThreadPoolTaskExecutor threadPoolTaskExecutor;
    @Test
    void contextLoads() throws InterruptedException {
        asyncTest.hello("async注解创建");
        threadPoolTaskExecutor.submit(new Thread(()->{
            logger.info("threadPoolTaskExecutor 创建线程");
        }));
        //一定要休眠 不然主线程关闭了,子线程还没有启动
        Thread.sleep(1000);
    }
}

查看打印的日志发现都成功创建线程!!!:

INFO 12360 --- [ task-2] c.h.s.t.t.ThreadpoolApplicationTests : threadPoolTaskExecutor 创建线程
INFO 12360 --- [ task-1] c.h.s.threadpool.threadpool.AsyncTest : 异步线程启动 started.async注解创建

备注1:如果只使用ThreadPoolTaskExecutor, 是可以不用在Application启动类上面加上@EnableAsync注解的哦!!!
备注2:多次测试发现ThreadPoolTaskExecutor执行比@Async要快!!!

线程池默认配置信息

以下是springboot默认的线程池配置,可以在application.properties文件当中进行相关的设置!!!

# 核心线程数
spring.task.execution.pool.core-size=8  
# 最大线程数
spring.task.execution.pool.max-size=16
# 空闲线程存活时间
spring.task.execution.pool.keep-alive=60s
# 是否允许核心线程超时
spring.task.execution.pool.allow-core-thread-timeout=true
# 线程队列数量
spring.task.execution.pool.queue-capacity=100
# 线程关闭等待
spring.task.execution.shutdown.await-termination=false
spring.task.execution.shutdown.await-termination-period=
# 线程名称前缀
spring.task.execution.thread-name-prefix=task-

深入springboot默认的线程池

根据官方文档的说明,Spring Boot auto-configures a ThreadPoolTaskExecutor 。最终找到springboot的线程池自动装配类:TaskExecutionAutoConfiguration

    @Bean
    @ConditionalOnMissingBean
    public TaskExecutorBuilder taskExecutorBuilder(TaskExecutionProperties properties, ObjectProvider<TaskExecutorCustomizer> taskExecutorCustomizers, ObjectProvider<TaskDecorator> taskDecorator) {
        Pool pool = properties.getPool();
        TaskExecutorBuilder builder = new TaskExecutorBuilder();
        builder = builder.queueCapacity(pool.getQueueCapacity());
        builder = builder.corePoolSize(pool.getCoreSize());
        builder = builder.maxPoolSize(pool.getMaxSize());
        builder = builder.allowCoreThreadTimeOut(pool.isAllowCoreThreadTimeout());
        builder = builder.keepAlive(pool.getKeepAlive());
        Shutdown shutdown = properties.getShutdown();
        builder = builder.awaitTermination(shutdown.isAwaitTermination());
        builder = builder.awaitTerminationPeriod(shutdown.getAwaitTerminationPeriod());
        builder = builder.threadNamePrefix(properties.getThreadNamePrefix());
        Stream var10001 = taskExecutorCustomizers.orderedStream();
        var10001.getClass();
        builder = builder.customizers(var10001::iterator);
        builder = builder.taskDecorator((TaskDecorator)taskDecorator.getIfUnique());
        return builder;
    }

同时在ThreadPoolTaskExecutor源码当中可以看到线程池的初始化方式是直接调用的ThreadPoolExecutor进行的初始化。

 protected ExecutorService initializeExecutor(ThreadFactory threadFactory, RejectedExecutionHandler rejectedExecutionHandler) {
        BlockingQueue<Runnable> queue = this.createQueue(this.queueCapacity);
        ThreadPoolExecutor executor;
        if (this.taskDecorator != null) {
            executor = new ThreadPoolExecutor(this.corePoolSize, this.maxPoolSize, (long)this.keepAliveSeconds, TimeUnit.SECONDS, queue, threadFactory, rejectedExecutionHandler) {
                public void execute(Runnable command) {
                    Runnable decorated = ThreadPoolTaskExecutor.this.taskDecorator.decorate(command);
                    if (decorated != command) {
                        ThreadPoolTaskExecutor.this.decoratedTaskMap.put(decorated, command);
                    }

                    super.execute(decorated);
                }
            };
        } else {
            executor = new ThreadPoolExecutor(this.corePoolSize, this.maxPoolSize, (long)this.keepAliveSeconds, TimeUnit.SECONDS, queue, threadFactory, rejectedExecutionHandler);
        }

        if (this.allowCoreThreadTimeOut) {
            executor.allowCoreThreadTimeOut(true);
        }

        this.threadPoolExecutor = executor;
        return executor;
    }

同时会发现默认的线程池拒绝策略是: AbortPolicy 直接抛出异常!!!

private RejectedExecutionHandler rejectedExecutionHandler = new AbortPolicy();

使用自定义的线程池

在默认配置信息里面是没有线程池的拒绝策略设置的方法的,如果需要更换拒绝策略就需要自定义线程池,并且如果项目当中需要多个自定义的线程池,又要如何进行管理呢?

自定义Configuration

第一步:创建一个ThreadPoolConfig 先只配置一个线程池,并设置拒绝策略为CallerRunsPolicy

@Configuration
public class ThreadPoolConfig {

    @Bean("taskExecutor")
    public Executor taskExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        //设置线程池参数信息
        taskExecutor.setCorePoolSize(10);
        taskExecutor.setMaxPoolSize(50);
        taskExecutor.setQueueCapacity(200);
        taskExecutor.setKeepAliveSeconds(60);
        taskExecutor.setThreadNamePrefix("myExecutor--");
        taskExecutor.setWaitForTasksToCompleteOnShutdown(true);
        taskExecutor.setAwaitTerminationSeconds(60);
        //修改拒绝策略为使用当前线程执行
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        //初始化线程池
        taskExecutor.initialize();
        return taskExecutor;
    }
}

然后执行之前写的测试代码发现,使用的线程池已经变成自定义的线程池了。

INFO 12740 --- [ myExecutor--2] c.h.s.t.t.ThreadpoolApplicationTests : threadPoolTaskExecutor 创建线程
INFO 12740 --- [ myExecutor--1] c.h.s.threadpool.threadpool.AsyncTest : 异步线程启动 started.async注解创建

第二步:如果配置有多个线程池,该如何指定线程池呢?

@Configuration
public class ThreadPoolConfig {

       @Bean("taskExecutor")
    public Executor taskExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        //设置线程池参数信息
        taskExecutor.setCorePoolSize(10);
        taskExecutor.setMaxPoolSize(50);
        taskExecutor.setQueueCapacity(200);
        taskExecutor.setKeepAliveSeconds(60);
        taskExecutor.setThreadNamePrefix("myExecutor--");
        taskExecutor.setWaitForTasksToCompleteOnShutdown(true);
        taskExecutor.setAwaitTerminationSeconds(60);
        //修改拒绝策略为使用当前线程执行
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        //初始化线程池
        taskExecutor.initialize();
        return taskExecutor;
    }

    @Bean("poolExecutor")
    public Executor poolExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        //设置线程池参数信息
        taskExecutor.setCorePoolSize(10);
        taskExecutor.setMaxPoolSize(50);
        taskExecutor.setQueueCapacity(200);
        taskExecutor.setKeepAliveSeconds(60);
        taskExecutor.setThreadNamePrefix("myExecutor2--");
        taskExecutor.setWaitForTasksToCompleteOnShutdown(true);
        taskExecutor.setAwaitTerminationSeconds(60);
        //修改拒绝策略为使用当前线程执行
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        //初始化线程池
        taskExecutor.initialize();
        return taskExecutor;
    }

    @Bean("taskPoolExecutor")
    public Executor taskPoolExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        //设置线程池参数信息
        taskExecutor.setCorePoolSize(10);
        taskExecutor.setMaxPoolSize(50);
        taskExecutor.setQueueCapacity(200);
        taskExecutor.setKeepAliveSeconds(60);
        taskExecutor.setThreadNamePrefix("myExecutor3--");
        taskExecutor.setWaitForTasksToCompleteOnShutdown(true);
        taskExecutor.setAwaitTerminationSeconds(60);
        //修改拒绝策略为使用当前线程执行
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        //初始化线程池
        taskExecutor.initialize();
        return taskExecutor;
    }
}

执行测试类,直接报错说找到多个类,不知道加载哪个类:

No qualifying bean of type 'org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor' available: expected single matching bean but found 3: taskExecutor,taskPoolExecutor

由于测试类当中是这样自动注入的:

@Autowired
ThreadPoolTaskExecutor threadPoolTaskExecutor; 

考虑到@Autowired 以及@Resource两个注入时的存在多个类如何匹配问题,然后发现只要我们在注入时指定具体的bean就会调用对应的线程池!!!

即修改测试类如下:

    @Autowired
    AsyncTest asyncTest;
    @Autowired
    ThreadPoolTaskExecutor poolExecutor; //会去匹配 @Bean("poolExecutor") 这个线程池
    @Test
    void contextLoads() throws InterruptedException {
        asyncTest.hello("async注解创建");
        //一定要休眠 不然主线程关闭了,子线程还没有启动
        poolExecutor.submit(new Thread(()->{
            logger.info("threadPoolTaskExecutor 创建线程");
        }));
        Thread.sleep(1000);
    }

最后得到如下信息:

INFO 13636 --- [ myExecutor2--1] c.h.s.t.t.ThreadpoolApplicationTests : threadPoolTaskExecutor 创建线程
INFO 13636 --- [ myExecutor--1] c.h.s.threadpool.threadpool.AsyncTest : 异步线程启动 started.async注解创建

备注1:如果是使用的@Async注解,只需要在注解里面指定bean的名称就可以切换到对应的线程池去了。如下所示:

	@Async("taskPoolExecutor")
    public void hello(String name){
        logger.info("异步线程启动 started."+name);
    }

备注2:如果有多个线程池,但是在@Async注解里面没有指定的话,会默认加载第一个配置的线程池

总结

线程池的四种拒绝策略:https://www.cnblogs.com/cblogs/p/9444557.html
JAVA常用的四种线程池: https://www.cnblogs.com/zhujiabin/p/5404771.html
线程池的使用是为了管理线程,但是对于线程池项目当中也是要管理起来的。有利于后续的维护!!!


标题:springboot之线程池ThreadPoolTaskExecutor以及@Async异步注解
作者:hjljy
地址:https://www.hjljy.cn/articles/2020/05/14/1589470484311.html