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 {
}