CJDBCversion1.0rc6: org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock class Reference

説明

バージョン:

1.0

TransactionExclusiveLock.java の 40 行で定義されています。


Public メソッド
boolean	acquire (AbstractRequest request)
synchronized void	release ()
boolean	isLocked ()
long	getLocker ()
ArrayList	getWaitingList ()
synchronized boolean	isWaiting (long transactionId)
Private 変数
boolean	isLocked = false
long	locker
ArrayList	waitingList = new ArrayList()

メソッド

boolean org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock.acquire

(

AbstractRequest

request

)

Acquires an exclusive lock on this table. If the lock is already held by the same transaction as the given request, this method is non-blocking else the caller is blocked until the transaction holding the lock releases it at commit/rollback time.

引数:

request

request asking for the lock (timeout field is used and updated upon waiting)

戻り値:: boolean true is the lock has been successfully acquired, false on timeout or error

参照:: release()

TransactionExclusiveLock.java の 107 行で定義されています。

参照先 org.objectweb.cjdbc.common.sql.AbstractRequest.getTimeout(), org.objectweb.cjdbc.common.sql.AbstractRequest.getTransactionId(), org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock.isLocked, org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock.locker, org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock.release(), org.objectweb.cjdbc.common.sql.AbstractRequest.setTimeout(), と org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock.waitingList.

参照元 org.objectweb.cjdbc.controller.scheduler.singledb.SingleDBPessimisticTransactionLevelScheduler.scheduleNonSuspendedWriteRequest(), org.objectweb.cjdbc.controller.scheduler.raidb2.RAIDb2PessimisticTransactionLevelScheduler.scheduleNonSuspendedWriteRequest(), org.objectweb.cjdbc.controller.scheduler.raidb1.RAIDb1PessimisticTransactionLevelScheduler.scheduleNonSuspendedWriteRequest(), と org.objectweb.cjdbc.controller.scheduler.raidb0.RAIDb0PessimisticTransactionLevelScheduler.scheduleNonSuspendedWriteRequest().

00108   {
00109     long tid = request.getTransactionId();
00110 
00111     synchronized (Thread.currentThread())
00112     {
00113       WaitingListElement wle = null;
00114       synchronized (this)
00115       {
00116         if (!isLocked)
00117         { // Lock is free, take it
00118           locker = tid;
00119           isLocked = true;
00120           return true;
00121         }
00122         else
00123         {
00124           if (locker == tid)
00125             return true; // We already have the lock
00126           else
00127           { // Wait for the lock
00128             wle = new WaitingListElement(Thread.currentThread(), tid);
00129             waitingList.add(wle);
00130           }
00131         }
00132       }
00133       // At this point, we have to wait for the lock.
00134       try
00135       {
00136         int timeout = request.getTimeout();
00137         if (timeout == 0)
00138         {
00139           Thread.currentThread().wait(); // No timeout
00140           // Note: isLocked and locker are already set.
00141           return true;
00142         }
00143         else
00144         { // Wait with timeout
00145           long start = System.currentTimeMillis();
00146           // Convert seconds to milliseconds for wait call
00147           long lTimeout = timeout * 1000;
00148           Thread.currentThread().wait(lTimeout);
00149           long end = System.currentTimeMillis();
00150           int remaining = (int) (lTimeout - (end - start));
00151           if (remaining > 0)
00152           { // Ok
00153             request.setTimeout(remaining);
00154             // Note: isLocked and locker are already set.
00155             return true;
00156           }
00157           else
00158           { // Too late, remove ourselves from the waiting list
00159             synchronized (this)
00160             {
00161               int idx = waitingList.indexOf(wle);
00162               if (idx == -1)
00163                 // We got the lock before being able to acquire the lock on
00164                 // this. Give the lock to the next one.
00165                 release();
00166               else
00167                 waitingList.remove(idx);
00168             }
00169             return false;
00170           }
00171         }
00172       }
00173       catch (InterruptedException ie)
00174       {
00175         synchronized (this)
00176         { // Something wrong happened, remove ourselves from the waiting list
00177           waitingList.remove(Thread.currentThread());
00178         }
00179         return false;
00180       }
00181     }
00182   }

boolean org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock.isLocked

(

)

Returns true if the lock is owned by someone.

戻り値:: boolean value

TransactionExclusiveLock.java の 212 行で定義されています。

00213   {
00214     return isLocked;
00215   }

00246 { 00247 WaitingListElement e; 00248 int size = waitingList.size(); 00249 for (int i = 0; i < size; i++) 00250 { 00251 e = (WaitingListElement) waitingList.get(i); 00252 if (e.getTransactionId() == transactionId) 00253 return true; 00254 } 00255 return false; 00256 }

00190 { 00191 while (!waitingList.isEmpty()) 00192 { 00193 // Wake up the first waiting thread and update locker transaction id 00194 WaitingListElement e = (WaitingListElement) waitingList.remove(0); 00195 Thread thread = e.getThread(); 00196 locker = e.getTransactionId(); 00197 synchronized (thread) 00198 { 00199 thread.notify(); 00200 // isLocked remains true 00201 return; 00202 } 00203 } 00204 isLocked = false; 00205 }

クラス org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock

説明

Public メソッド

Private 変数

メソッド

変数