ThreadPoolTaskExecutor在执行线程时，存在一个
TaskDecorator配置，可以装饰线程类。
1. 源码分析
源码：org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor#initializeExecutor
@Override protected ExecutorService initializeExecutor(ThreadFactory threadFactory, RejectedExecutionHandler rejectedExecutionHandler) {
BlockingQueue < Runnable > queue = createQueue(this.queueCapacity);
ThreadPoolExecutor executor;
//配置了线程装饰器
if (this.taskDecorator != null) {
executor = new ThreadPoolExecutor(this.corePoolSize, this.maxPoolSize, this.keepAliveSeconds, TimeUnit.SECONDS, queue, threadFactory, rejectedExecutionHandler) {@Override public void execute(Runnable command) {
//装饰线程类
Runnable decorated = taskDecorator.decorate(command);
if (decorated != command) {
decoratedTaskMap.put(decorated, command);
}
//执行原有逻辑
super.execute(decorated);
}
};
} else {
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;
}
2. 实际使用
声明spring线程池时，需要指定TaskDecorator，在装饰代码中获取到ThreadLocal的值。
@Configuration
@EnableAsync
public class ThreadPoolConfig {
@Bean("asyncServiceExecutor")
public ThreadPoolTaskExecutor asyncRabbitTimeoutServiceExecutor() {
ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();
//核心线程数
threadPoolTaskExecutor.setCorePoolSize(5);
//核心线程若处于闲置状态的话，超过一定的时间(KeepAliveTime)，就会销毁掉。
threadPoolTaskExecutor.setAllowCoreThreadTimeOut(true);
//最大线程数
threadPoolTaskExecutor.setMaxPoolSize(10);
//配置队列大小
threadPoolTaskExecutor.setQueueCapacity(300);
//加入装饰器
threadPoolTaskExecutor.setTaskDecorator(new ContextCopyingDecorator());
//配置线程池前缀
threadPoolTaskExecutor.setThreadNamePrefix("test-log-");
//拒绝策略:只要线程池未关闭，该策略直接在调用者线程中串行运行被丢弃的任务，显然这样不会真的丢弃任务，但是可能会造成调用者性能急剧下降
threadPoolTaskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
threadPoolTaskExecutor.initialize();
return threadPoolTaskExecutor;
}
@Slf4j
static class ContextCopyingDecorator implements TaskDecorator {
@Nonnull
@Override
public Runnable decorate(@Nonnull Runnable runnable) {
//主流程
String res = TestMappingController.local.get();
log.info("装饰前：" + res);
//子线程逻辑
return () -> {
try {
//将变量重新放入到run线程中。
TestMappingController.local.set(res);
log.info("打印日志-开始");
runnable.run();
} finally {
log.info("打印日志-结束");
}
};
}
}
}
业务逻辑：
@PostMapping("test2")
public void test() {
//主线程执行
local.set("主线程设置的ThreadLocal");
//子线程执行
executor.execute(() - >{
String res = local.get();
log.info("线程:" + res);
});
}
执行结果：可以看到，在ContextCopyingDecorator中是主线程在调用，所以可以获取到主线程的ThreadLocal信息。
2020-11-17 18:54:25,027 INFO [1747069] [http-nio-8087-exec-5] [] (ThreadPoolConfig.java:53): 装饰前：主线程设置的ThreadLocal
2020-11-17 18:54:25,028 INFO [1747070] [test-log-4] [] (ThreadPoolConfig.java:59): 打印日志-开始
2020-11-17 18:54:25,028 INFO [1747070] [test-log-4] [] (TestMappingController.java:46): 线程:主线程设置的ThreadLocal
2020-11-17 18:54:25,028 INFO [1747070] [test-log-4] [] (ThreadPoolConfig.java:62): 打印日志-结束
