Java线程池在运行后的结果反查
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参考技术AJava线程池需要不断的学习 在学习的时候我们就要注意不少的问题 下面我们就来看看具体的语言运作环境如何才能满足Java线程池相关程序的运行 希望大家有所收获
无论是接收Runnable型参数 还是接收Callable型参数的submit()方法 都会返回一个Future(也是一个接口)类型的对象 该对象中包含了任务的执行情况以及结果 调用Future的boolean isDone()方法可以获知任务是否执行完毕 调用Object get()方法可以获得任务执行后的返回结果 如果此时任务还没有执行完 get()方法会保持等待 直到相应的任务执行完毕后 才会将结果返回
我们用下面的一个例子来演示Java 中Java线程池的使用
Java代码
import ncurrent *;
public class ExecutorTest
public static void main(String[] args) throws
InterruptedException
ExecutionException
ExecutorService es = Executors newSingleThreadExecutor();
Future fr = es submit(new RunnableTest());// 提交任务
Future fc = es submit(new CallableTest());// 提交任务
// 取得返回值并输出
System out println((String) fc get());
// 检查任务是否执行完毕
if (fr isDone())
System out println( 执行完毕 RunnableTest run() );
else
System out println( 未执行完 RunnableTest run() );
// 检查任务是否执行完毕
if (fc isDone())
System out println( 执行完毕 CallableTest run() );
else
System out println( 未执行完 CallableTest run() );
// 停止线程池服务
es shutdown();
class RunnableTest implements Runnable
public void run()
System out println( 已经执行 RunnableTest run() );
class CallableTest implements Callable
public Object call()
System out println( 已经执行 CallableTest call() );
return 返回值 CallableTest call() ;
import ncurrent *;
public class ExecutorTest
public static void main(String[] args) throws
InterruptedException
ExecutionException
ExecutorService es = Executors newSingleThreadExecutor();
Future fr = es submit(new RunnableTest());// 提交任务
Future fc = es submit(new CallableTest());// 提交任务
// 取得返回值并输出
System out println((String) fc get());
// 检查任务是否执行完毕
if (fr isDone())
System out println( 执行完毕 RunnableTest run() );
else
System out println( 未执行完 RunnableTest run() );
// 检查任务是否执行完毕
if (fc isDone())
System out println( 执行完毕 CallableTest run() );
else
System out println( 未执行完 CallableTest run() );
// 停止线程池服务
es shutdown();
class RunnableTest implements Runnable
public void run()
System out println( 已经执行 RunnableTest run() );
class CallableTest implements Callable
public Object call()
System out println( 已经执行 CallableTest call() );
return 返回值 CallableTest call() ;
运行结果
已经执行 RunnableTest run()
已经执行 CallableTest call()
返回值 CallableTest call()
执行完毕 RunnableTest run()
执行完毕 CallableTest run()
lishixinzhi/Article/program/Java/gj/201311/27283
使用阻塞队列的对象池在死锁中运行
我有一个在payara 5中运行的java应用程序。
我需要汇集我的bean将使用的一些引擎对象(来自库)。创建引擎需要在单独的线程中完成。
为此我想出了我的EnginePool和我的EngineProducer。想法是EnginePool管理两个BlockingQueues。一个用于可用引擎,另一个用于bean使用的引擎,需要再次使用。 EnginePool应该只提供一次,因此它是一个单例。
@Singleton
@Startup
@LocalBean
@TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
public class AbbyyEnginePool implements OcrEnginePool<IEngine> {
private static final Logger logger = LoggerFactory.getLogger(AbbyyEnginePool.class);
@Resource(lookup = "java:comp/DefaultManagedThreadFactory")
private ManagedThreadFactory threadFactory;
private static final int DEFAULT_ENGINE_COUNT = 3;
private BlockingQueue<EngineMetaInfo> availableEngines = new ArrayBlockingQueue<>(DEFAULT_ENGINE_COUNT);
private BlockingQueue<IEngine> enginesToRelease = new ArrayBlockingQueue<>(DEFAULT_ENGINE_COUNT);
private Map<IEngine, IEngine> proxiesMapping = new ConcurrentHashMap<>(DEFAULT_ENGINE_COUNT);
private int poolSize;
public AbbyyEnginePool() {
this(DEFAULT_ENGINE_COUNT);
}
public AbbyyEnginePool(int poolSize) {
this.poolSize = poolSize;
availableEngines = new ArrayBlockingQueue<>(poolSize);
enginesToRelease = new ArrayBlockingQueue<>(poolSize);
proxiesMapping = new ConcurrentHashMap<>(poolSize);
}
void setThreadFactory(ManagedThreadFactory threadFactory) {
this.threadFactory = threadFactory;
}
@PostConstruct
void init() {
EngineProducer engineProducer = new EngineProducer(availableEngines, enginesToRelease, poolSize);
Thread engineProducerThread = threadFactory.newThread(engineProducer);
engineProducerThread.setName("engineProducer");
engineProducerThread.start();
}
@Override
public IEngine get() throws EngineException {
try {
EngineMetaInfo engineMetaInfo = availableEngines.take();
IEngine engineProxy = IEngine.UnmarshalInterface(engineMetaInfo.engineHandle);
proxiesMapping.put(engineProxy, engineMetaInfo.engine);
return engineProxy;
} catch (InterruptedException e) {
throw new EngineException("Could not retrieve engine", e);
}
}
@Override
public void release(IEngine engineProxy) throws EngineException {
if (engineProxy != null) {
synchronized (proxiesMapping) {
if (proxiesMapping.containsKey(engineProxy)) {
try {
IEngine engine = proxiesMapping.remove(engineProxy);
enginesToRelease.put(engine);
} catch (Exception e) {
throw new EngineException("Could not release engine proxy.");
}
} else {
logger.warn("Engine proxy was not registered. Could not release proxy.");
}
}
}
}
static class EngineMetaInfo {
long engineHandle;
IEngine engine;
EngineMetaInfo(long engineHandle, IEngine engine) {
this.engineHandle = engineHandle;
this.engine = engine;
}
}
}
EngineProducer看起来像这样:
public class EngineProducer implements Runnable {
private static final Logger logger = LoggerFactory.getLogger(EngineProducer.class);
private static final String PROJECT_ID = "someId";
private final Integer MAX_ENGINE_COUNT;
private final BlockingQueue<AbbyyEnginePool.EngineMetaInfo> availableEngines;
private final BlockingQueue<IEngine> enginesToRelease;
private Boolean isRunning = Boolean.FALSE;
private List<EngineHolder> enginesHolder;
public EngineProducer(BlockingQueue<AbbyyEnginePool.EngineMetaInfo> availableEngines,
BlockingQueue<IEngine> enginesToRelease,
Integer maxEnginesCount) {
this.availableEngines = availableEngines;
this.enginesToRelease = enginesToRelease;
this.MAX_ENGINE_COUNT = maxEnginesCount;
this.enginesHolder = new ArrayList<>(MAX_ENGINE_COUNT);
}
private void initEngines() {
synchronized (availableEngines) {
if (availableEngines.size() == 0) {
try {
for (int i = 0; i < MAX_ENGINE_COUNT; i++) {
EngineHolder engineHolder = new EngineHolder(PROJECT_ID);
enginesHolder.add(engineHolder);
IEngine engine = engineHolder.getAndLockEngine();
long engineHandle = engine.MarshalInterface();
AbbyyEnginePool.EngineMetaInfo engineMetaInfo = new AbbyyEnginePool.EngineMetaInfo(engineHandle, engine);
availableEngines.put(engineMetaInfo);
}
logger.info("{} abbyy engines prepared for processing", MAX_ENGINE_COUNT);
EnginePool.setInitialized(Boolean.TRUE);
isRunning = Boolean.TRUE;
} catch (Exception e) {
logger.error("Could not instantiate engines.", e);
}
}
}
}
@Override
public void run() {
try {
initEngines();
while(isRunning) {
IEngine engineProxyToRelease = enginesToRelease.take();
releaseEngine(engineProxyToRelease);
}
availableEngines.clear();
for(int i = 0; i < enginesHolder.size(); i++) {
enginesHolder.get(i).unloadEngine();
}
} catch (Exception e) {
logger.error("EngineProducer encounter a problem.", e);
}
}
public void unloadEngines() {
isRunning = Boolean.FALSE;
}
private void releaseEngine( IEngine engineToRelease ) {
for (EngineHolder engineHolder : enginesHolder) {
if (engineHolder.containsEngine(engineToRelease)) {
engineHolder.unlockEngine();
IEngine engine = engineHolder.getAndLockEngine();
long engineHandle = engine.MarshalInterface();
AbbyyEnginePool.EngineMetaInfo engineMetaInfo = new AbbyyEnginePool.EngineMetaInfo(engineHandle, engine);
try {
availableEngines.put(engineMetaInfo);
} catch (InterruptedException e) {
logger.warn("could not add free engine");
}
break;
}
}
}
}
当我在测试中运行它而不是在glassfish中运行它时没有问题。但是当我在玻璃鱼中运行时,豆子会陷入僵局。
bean使用此代码来获取和释放引擎:
engine = enginePool.get();
ProcessingResult processingResult = null;
try {
this.parameters = parameters;
this.tmpDir = tmpDir;
Path customProfileFile = loadProfiles(parameters);
Instant processingStart = Instant.now();
processingResult = processFile();
Instant processingEnd = Instant.now();
enginePool.release(engine);
engine = null;
processingResult.setProcessingStartTime(processingStart);
processingResult.setProcessingEndTime(processingEnd);
logger.info("Processing took about {} milliseconds.", processingResult.getProcessDurationInMilliseconds());
customProfileFile.toFile().delete();
this.tmpDir.toFile().delete();
} catch (Exception e) {
logger.error("Ocr of document failed ",e );
enginePool.release(engine);
throw new EngineException("Ocr of document failed.", e);
}
在我的场景中有4个尝试获取引擎的bean。其中3个将获得一个,最后一个bean将等待engine = enginePool.get();
3个获得引擎的bean将完成他们的工作并等待enginePool.release(engine);
。我接受了一个线程转储,可以看到3个bean正在等待一个没有引擎的bean所持有的锁。所以他们无法释放引擎。
我的问题是我不明白。释放和获取引擎在不同的阻塞队列上工作,所以我想知道为什么等待获取引擎的最后一个bean阻止试图释放引擎的其他bean。
问题是容器管理所有并发。如果是单例,则意味着对字段的所有访问都将获得写锁定。
解决方案是使用@ConcurrencyManagement(BEAN)注释。这意味着bean控制并发管理,并且必须确保完成同步。
详细解释可以在here找到。
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