Spring线程池ThreadPoolTaskExecutor配置及详情

Spring线程池ThreadPoolTaskExecutor配置及详情

1. ThreadPoolTaskExecutor配置

 <!-- spring thread pool executor -->
     <bean id="taskExecutor" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor">
         <!-- 线程池维护线程的最少数量 -->
         <property name="corePoolSize" value="5" />
         <!-- 允许的空闲时间 -->
         <property name="keepAliveSeconds" value="200" />
         <!-- 线程池维护线程的最大数量 -->
         <property name="maxPoolSize" value="10" />
         <!-- 缓存队列 -->
         <property name="queueCapacity" value="20" />
         <!-- 对拒绝task的处理策略 -->
         <property name="rejectedExecutionHandler">
             <bean class="java.util.concurrent.ThreadPoolExecutor$CallerRunsPolicy" />
         </property>
     </bean>

属性字段说明

corePoolSize：线程池维护线程的最少数量

keepAliveSeconds：允许的空闲时间

maxPoolSize：线程池维护线程的最大数量

queueCapacity：缓存队列

rejectedExecutionHandler：对拒绝task的处理策略

2. execute(Runable)方法执行过程

如果此时线程池中的数量小于corePoolSize，即使线程池中的线程都处于空闲状态，也要创建新的线程来处理被添加的任务。

如果此时线程池中的数量等于 corePoolSize，但是缓冲队列 workQueue未满，那么任务被放入缓冲队列。

如果此时线程池中的数量大于corePoolSize，缓冲队列workQueue满，并且线程池中的数量小于maxPoolSize，建新的线程来处理被添加的任务。

如果此时线程池中的数量大于corePoolSize，缓冲队列workQueue满，并且线程池中的数量等于maxPoolSize，那么通过handler所指定的策略来处理此任务。也就是：处理任务的优先级为：核心线程corePoolSize、任务队列workQueue、最大线程 maximumPoolSize，如果三者都满了，使用handler处理被拒绝的任务。

当线程池中的线程数量大于corePoolSize时，如果某线程空闲时间超过keepAliveTime，线程将被终止。这样，线程池可以动态的调整池中的线程数。

3. 示例代码

Junit Test

 @RunWith(SpringJUnit4ClassRunner.class)
 @ContextConfiguration(classes = { MultiThreadConfig.class })
 public class MultiThreadTest {

     @Autowired
     private ThreadPoolTaskExecutor taskExecutor;

     @Autowired
     private MultiThreadProcessService multiThreadProcessService;

     @Test
     public void test() {

         int n = 20;
         for (int i = 0; i < n; i++) {
             taskExecutor.execute(new MultiThreadDemo(multiThreadProcessService));
             System.out.println("int i is " + i + ", now threadpool active threads totalnum is " + taskExecutor.getActiveCount());
         }

         try {
             System.in.read();
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
     }
 }

MultiThreadDemo

 /**
  * 多线程并发处理demo
  * @author daniel.zhao
  *
  */
 public class MultiThreadDemo implements Runnable {

     private MultiThreadProcessService multiThreadProcessService;

     public MultiThreadDemo() {
     }

     public MultiThreadDemo(MultiThreadProcessService multiThreadProcessService) {
         this.multiThreadProcessService = multiThreadProcessService;
     }

     @Override
     public void run() {
         multiThreadProcessService.processSomething();
     }

 }

MultiThreadProcessService

 @Service
 public class MultiThreadProcessService {

     public static final Logger logger = Logger.getLogger(MultiThreadProcessService.class);

     /**
      * 默认处理流程耗时1000ms
      */
     public void processSomething() {
         logger.debug("MultiThreadProcessService-processSomething" + Thread.currentThread() + "......start");
         try {
             Thread.sleep(1000);
         } catch (InterruptedException e) {
             throw new RuntimeException(e);
         }
         logger.debug("MultiThreadProcessService-processSomething" + Thread.currentThread() + "......end");
     }
 }

MultiThreadConfig

 @Configuration
 @ComponentScan(basePackages = { "com.xxx.multithread" })
 @ImportResource(value = { "classpath:config/application-task.xml" })
 @EnableScheduling
 public class MultiThreadConfig {
 }