spring的 ThreadPoolTaskExecutor类最终是通过调用java 的ThreadPoolExecutor的void execute(Runnable task)方法或Future<?> submit(Runnable task)方法执行任务的
下面是spring的任务执行类和接口的继承层次
interface Executor
void execute(Runnable command);
interface TaskExecutor extends Executor
void execute(Runnable task);
interface AsyncTaskExecutor extends TaskExecutor
void execute(Runnable task, long startTimeout);
Future<?> submit(Runnable task);
<T> Future<T> submit(Callable<T> task);
interface SchedulingTaskExecutor extends AsyncTaskExecutor
boolean prefersShortLivedTasks();
任务执行类
class ThreadPoolTaskExecutor extends ExecutorConfigurationSupport implements SchedulingTaskExecutor
成员变量
private ThreadPoolExecutor threadPoolExecutor;
执行任务方法
public void execute(Runnable task) {
Executor executor = getThreadPoolExecutor();
try {
executor.execute(task);
}
catch (RejectedExecutionException ex) {
throw new TaskRejectedException("Executor [" + executor + "] did not accept task: " + task, ex);
}
}
public ThreadPoolExecutor getThreadPoolExecutor() throws IllegalStateException {
Assert.state(this.threadPoolExecutor != null, "ThreadPoolTaskExecutor not initialized");
return this.threadPoolExecutor;
}
基类ExecutorConfigurationSupport
abstract class ExecutorConfigurationSupport extends CustomizableThreadFactory
implements BeanNameAware, InitializingBean, DisposableBean
其中基类CustomizableThreadFactory为自定义线程工厂类
成员变量
private ExecutorService executor;
生命周期初始化
public void afterPropertiesSet() {
initialize();
}
初始化方法
/**
* Set up the ExecutorService.
*/
public void initialize() {
if (logger.isInfoEnabled()) {
logger.info("Initializing ExecutorService " + (this.beanName != null ? " '" + this.beanName + "'" : ""));
}
if (!this.threadNamePrefixSet && this.beanName != null) {
setThreadNamePrefix(this.beanName + "-");
}
this.executor = initializeExecutor(this.threadFactory, this.rejectedExecutionHandler);
}
抽象方法（子类ThreadPoolTaskExecutor实现）
protected abstract ExecutorService initializeExecutor(
ThreadFactory threadFactory, RejectedExecutionHandler rejectedExecutionHandler);
生命周期销毁方法
public void destroy() {
shutdown();
}
ThreadPoolTaskExecutor实现ExecutorService initializeExecutor(ThreadFactory threadFactory, RejectedExecutionHandler rejectedExecutionHandler);方法
protected ExecutorService initializeExecutor(
ThreadFactory threadFactory, RejectedExecutionHandler rejectedExecutionHandler) {
BlockingQueue<Runnable> queue = createQueue(this.queueCapacity);
ThreadPoolExecutor executor = new ThreadPoolExecutor(
this.corePoolSize, this.maxPoolSize, this.keepAliveSeconds, TimeUnit.SECONDS,
queue, threadFactory, rejectedExecutionHandler);
if (this.allowCoreThreadTimeOut) {
executor.allowCoreThreadTimeOut(true);
}
this.threadPoolExecutor = executor;
return executor;
}
我们注意到上面的方法 initializeExecutor(ThreadFactory threadFactory, RejectedExecutionHandler rejectedExecutionHandler)是父类ExecutorConfigurationSupport调用的，初始化父类成员变量private ExecutorService executor;
而ThreadPoolTaskExecutor实际执行任务是采用的自身成员变量private ThreadPoolExecutor threadPoolExecutor;
public ThreadPoolExecutor getThreadPoolExecutor() throws IllegalStateException {
Assert.state(this.threadPoolExecutor != null, "ThreadPoolTaskExecutor not initialized");
return this.threadPoolExecutor;
}
不明白这里为什么要这么处理？
再看其他部分
ExecutorConfigurationSupport 里面配置默认拒绝策略
private RejectedExecutionHandler rejectedExecutionHandler = new ThreadPoolExecutor.AbortPolicy();
ThreadPoolTaskExecutor成员变量
private int corePoolSize = 1;
private int maxPoolSize = Integer.MAX_VALUE;//默认最大线程池
private int keepAliveSeconds = 60;
private boolean allowCoreThreadTimeOut = false;
private int queueCapacity = Integer.MAX_VALUE;//默认队列容量
阻塞队列创建方法
protected BlockingQueue<Runnable> createQueue(int queueCapacity) {
if (queueCapacity > 0) {
return new LinkedBlockingQueue<Runnable>(queueCapacity);
}
else {
return new SynchronousQueue<Runnable>();
}
}
