EJB中的Thread.sleep()
EJB中的Thread.sleep()
提问于 2011-11-20 23:20:34
我知道扰乱EJB中的线程是一个很大的禁忌，但我只是想请教一下如何处理这种情况。我的EJB正在调用一个外部Web服务，该服务有时可能会返回“忙”状态。当发生这种情况时，我想等待一段时间，然后使用与以前相同的数据重新提交请求。
实现这一点的最佳方式是什么？
回答 3
Stack Overflow用户
发布于 2011-11-20 23:37:01
EJB3.1带来了一个新的@Asynchronous feature，您可以利用它：
@Asynchronous
@TransactionAttribute(NOT_SUPPORTED)
public Future<WebServiceResult> callWebService(int retries) {
WebServiceResult result = webService.call();
if (!result.equals(BUSY)) {
return result;
}
if (retries <= 0) {
throw new TooBusyException();
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
return callWebService(retries - 1);
}然后简单地使用以下命令调用您的web服务：
Future<WebServiceResult> result = yourEJB.callWebService(1);
// Can do some interesting stuff here.
// ...
// ...
result.get(2, SECONDS); // Block for up to 2 seconds.正如您所看到的，您可以免费获得可配置的重试次数和超时。
这与仅仅调用Thread.sleep()有什么不同？返回Future更明确，也更易于管理。我也不认为Thread.sleep()是那么有害的。唯一的问题是这个EJB实例现在可以被其他客户端重用。使用Future，异步调用发生在其他某个EJB和线程池中。关于catch块中Thread#interrupt()的重要性，请参阅Why invoke Thread.currentThread.interrupt() when catch any InterruptException?
另一个想法:围绕调用web服务使用aspect，捕获BusyException一次，然后重试。
Stack Overflow用户
发布于 2015-08-12 02:11:42
但是外部web服务是外部的，并且您正在打开到它的网络连接，并且您希望执行一些管理工作。这就是JCA的用途，而不是EJB。
Stack Overflow用户
发布于 2020-04-25 04:40:44
以下是简单控件池的一个建议(或替代方法)：
1-将您的上下文(EJB)作为参数传递给您的方法(rest端点、调度器、默认方法)
2-使用互补的调度器或实体标志控制状态
3-注意数据量/处理量
4-推荐:强烈推荐指标、日志和测试、测试、测试
5-这段代码在SpringBoot上，但在Jboss中(经过修改)在EJB Context下进行了测试--仔细测试
6-根据需要使用/修改：(发送建议/评论)
BaseControlExecutor.java
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class BaseControlExecutor {
private final ScheduledThreadPoolExecutor poolExec = new ScheduledThreadPoolExecutor(2);
public void execWithTimeout(final Runnable runnable, long timeout,
TimeUnit timeUnit) throws Exception {
execWithTimeout(new Callable<Object>() {
@Override
public Object call() throws Exception {
runnable.run();
return null;
}
}, timeout, timeUnit);
}
public <T> T execWithTimeout(Callable<T> callable, long timeout, TimeUnit timeUnit) throws Exception {
final Future<T> future = poolExec.submit(callable);
try {
return future.get(timeout, timeUnit);
} catch (TimeoutException e) {
future.cancel(true);
throw e;
} catch (ExecutionException e) {
Throwable t = e.getCause();
if (t instanceof Error) {
throw (Error) t;
} else if (t instanceof Exception) {
throw (Exception) t;
} else {
throw new IllegalStateException(t);
}
}
}
}EndpointControlRest.java
import java.time.Duration;
import java.time.Instant;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicLong;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
@RestController
@RequestMapping(value = "/report")
@Api(tags = "Endpoint of Future")
public class EndpointControlRest extends BaseControlExecutor {
Logger logger = LoggerFactory.getLogger(EndpointControlRest.class);
//single metric of execution
protected final AtomicLong counter = new AtomicLong();
@GetMapping(path = "/withThread", produces = { "application/json" })
@ApiOperation(value = "Return Hello count.")
public String greeting() {
Long countRunner = counter.incrementAndGet();
String json = ""; //or EJB context to use in Thread - becareful
new Thread(() -> {
try {
execWithTimeout(new Runnable() {
@Override
public void run() {
Instant start = Instant.now();
logger.info("Report init - " + countRunner);
//generating reports
generateBackgroundReport(json);
logger.info("Report End - " + countRunner);
Instant finish = Instant.now();
long timeElapsed = Duration.between(start, finish).toMillis();
logger.info("###DEBUG - " + countRunner + " - OK |Time exe: " + timeElapsed);
}
}, 120, TimeUnit.SECONDS);
} catch (TimeoutException e) {
logger.info("###DEBUG - " + countRunner + " - Timeout - " + e.getMessage());
} catch (Exception e) {
logger.info("###DEBUG - " + countRunner + " - Exception - " + e.getMessage());
}
}).start();
logger.info("####DEBUG - Rest call released");
return "Hello " + countRunner;
}
public String generateBackgroundReport(String json){
//simulating work
Long x = 0L;
for(Long i = 0L; i < 1000000000L; i ++){
x = i + 1;
}
logger.info("####DEBUG -report: " + x);
return "OK";
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/8202492
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