线程池参数-SpringBoot配置线程池

先线程池有几个核心的参数概念：

1. 核心线程数（corePoolSize）

   线程池中会维护一个最小的线程数量，即使这些线程处理空闲状态，他们也不会被销毁，除非设置了allowCoreThreadTimeOut。这里的最小线程数量即是corePoolSize。任务提交到线程池后，首先会检查当前线程数是否达到了corePoolSize，如果没有达到的话，则会创建一个新线程来处理这个任务。

2. 最大线程数（maximumPoolSize）

   当前线程数达到corePoolSize后，如果继续有任务被提交到线程池，会将任务缓存到工作队列（后面会介绍）中。如果队列也已满，则会去创建一个新线程来出来这个处理。线程池不会无限制的去创建新线程，它会有一个最大线程数量的限制，这个数量即由maximunPoolSize指定。

3. 活跃时间/空闲线程存活时间（keepAliveTime）

   一个线程如果处于空闲状态，并且当前的线程数量大于corePoolSize，那么在指定时间后，这个空闲线程会被销毁，这里的指定时间由keepAliveTime来设定

4. 空闲线程存活时间的单位（unit）

   是指空闲线程存活时间的单位。keepAliveTime的计量单位。枚举类型TimeUnit类。线程空闲时间的单位，可以是秒、毫秒等。

5. 阻塞队列/线程工作队列（workQueue）

   1. ArrayBlockingQueue FIFO有界阻塞队列
   2. LinkedBlockingQueue FIFO无限队列
   3. SynchronousQueue不缓存任务的阻塞队列
   4. PriorityBlockingQueue具有优先级的无界阻塞队列，优先级通过参数Comparator实现。

6. 线程工厂（threadFactory）

   创建一个新线程时使用的工厂，可以用来设定线程名、是否为daemon线程等等，一般使用默认的ThreadFactory即可。

7. 超出线程数和工作队列时候的任务请求处理策略/拒绝策略（handler）

   当工作队列中的任务已到达最大限制，并且线程池中的线程数量也达到最大限制，这时如果有新任务提交进来，该如何处理呢。对新任务的处理策略，可以是抛出异常、丢弃任务等。这里的拒绝策略，就是解决这个问题的，jdk中提供了4中拒绝策略：

   • 策略1：ThreadPoolExecutor.AbortPolicy（默认）拒绝执行
   • 策略2：ThreadPoolExecutor.CallerRunsPolicy调用 execute 方法的线程本身运行任务
   • 策略3：ThreadPoolExecutor.DiscardOldestPolicy执行程序未关闭，则删除工作队列头部的任务
   • 策略4：ThreadPoolExecutor.DiscardPolicy无法执行的任务被简单地删除

public ThreadPoolExecutor(int corePoolSize,int maximumPoolSize,long keepAliveTime,TimeUnit unit,BlockingQueue<Runnable> workQueue,ThreadFactory threadFactory,RejectedExecutionHandler handler) {
原生使用
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(3, 10, 30, TimeUnit.SECONDS, new ArrayBlockingQueue<>(4),Executors.defaultThreadFactory(), new ThreadPoolExecutor.DiscardOldestPolicy());

spring使用

配置文件
@Configuration
@EnableAsync
public class ThreadPoolConfig {/*** 下面的配置是配置Springboot的@Async注解所用的线程池*/@Bean("taskExecutor")public Executor taskExecutor() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();// 设置线程池核心容量executor.setCorePoolSize(4);// 设置线程池最大容量executor.setMaxPoolSize(8);// 设置任务队列长度executor.setQueueCapacity(200);// 设置线程超时时间executor.setKeepAliveSeconds(60);// 设置线程名称前缀executor.setThreadNamePrefix("xyjAsyncPool-");// 设置任务丢弃后的处理策略,当poolSize已达到maxPoolSize,如何处理新任务(是拒绝还是交由其它线程处理)// CallerRunsPolicy: 不在新线程中执行任务,而是由调用者所在的线程来执executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());executor.initialize();return executor;}
}配置测试接口及其实现类
public interface TestAsync {void doAsync();
}@Service
@Slf4j
public class TestAsyncImpl implements TestAsync {@Override//使用@Async，并将前面的注册的bean，填写到Async的value中@Async("taskExecutor")public void doAsync() {log.info("== async start==");log.info("线程{}执行代码逻辑",Thread.currentThread().getName());log.info("== async end==");}
}测试
@SpringBootTest
public class AsyncTest {//引用类@Autowiredprivate TestAsync testAsync;@Testvoid test(){for (int i = 0; i < 10; i++) {testAsync.doAsync();}}
}
结果
2023-01-29 16:47:12.491  INFO 13332 --- [ taskExecutor-1] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.491  INFO 13332 --- [ taskExecutor-3] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.493  INFO 13332 --- [ taskExecutor-5] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.493  INFO 13332 --- [ taskExecutor-6] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.493  INFO 13332 --- [ taskExecutor-1] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.501  INFO 13332 --- [ taskExecutor-9] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.501  INFO 13332 --- [taskExecutor-10] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.500  INFO 13332 --- [ taskExecutor-7] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.502  INFO 13332 --- [ taskExecutor-8] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.500  INFO 13332 --- [ taskExecutor-7] c.w.a.service.async.impl.TestAsyncImpl   : == async start==
2023-01-29 16:47:12.502  INFO 13332 --- [ taskExecutor-6] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-6执行代码逻辑
2023-01-29 16:47:12.501  INFO 13332 --- [ taskExecutor-8] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-8执行代码逻辑
2023-01-29 16:47:12.503  INFO 13332 --- [ taskExecutor-5] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.492  INFO 13332 --- [ taskExecutor-9] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-9执行代码逻辑
2023-01-29 16:47:12.503  INFO 13332 --- [ taskExecutor-2] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.503  INFO 13332 --- [ taskExecutor-7] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.501  INFO 13332 --- [ taskExecutor-9] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-9执行代码逻辑
2023-01-29 16:47:12.492  INFO 13332 --- [ taskExecutor-1] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-1执行代码逻辑
2023-01-29 16:47:12.506  INFO 13332 --- [ taskExecutor-1] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.506  INFO 13332 --- [ taskExecutor-9] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.493  INFO 13332 --- [ taskExecutor-3] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-3执行代码逻辑
2023-01-29 16:47:12.501  INFO 13332 --- [taskExecutor-10] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-10执行代码逻辑
2023-01-29 16:47:12.506  INFO 13332 --- [ taskExecutor-3] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.506  INFO 13332 --- [taskExecutor-10] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.502  INFO 13332 --- [ taskExecutor-8] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-8执行代码逻辑
2023-01-29 16:47:12.506  INFO 13332 --- [ taskExecutor-8] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.502  INFO 13332 --- [ taskExecutor-7] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-7执行代码逻辑
2023-01-29 16:47:12.508  INFO 13332 --- [ taskExecutor-7] c.w.a.service.async.impl.TestAsyncImpl   : == async end==
2023-01-29 16:47:12.493  INFO 13332 --- [ taskExecutor-4] c.w.a.service.async.impl.TestAsyncImpl   : 线程taskExecutor-4执行代码逻辑
2023-01-29 16:47:12.508  INFO 13332 --- [ taskExecutor-4] c.w.a.service.async.impl.TestAsyncImpl   : == async end==