com.sleepycat.bdb
Class TransactionRunner

java.lang.Object
  |
  +--com.sleepycat.bdb.TransactionRunner

public class TransactionRunner

extends Object

Starts a transaction, calls TransactionWorker.doWork(), and handles transaction retry and exceptions.

Constructor Summary

TransactionRunner(DbEnv env)
Creates a transaction runner for a given Berkeley DB environment.

TransactionRunner(DbEnv env, int maxRetries)
Creates a transaction runner for a given Berkeley DB environment and with a given number of maximum retries.

Method Summary

boolean	getDirtyRead() Returns whether transactions will read data that is modified by another transaction but not committed.
int	getMaxRetries() Returns the maximum number of retries that will be performed when deadlocks are detected.
boolean	getNoWait() Returns whether transactions will throw DbLockNotGrantedException instead of blocking when trying to access data that is locked by another transaction.
void	run(TransactionWorker worker) Calls the TransactionWorker.doWork() method and, for transactional environments, begins and ends a transaction.
void	setDirtyRead(boolean dirtyRead) Changes whether transactions will read data that is modified by another transaction but not committed.
void	setMaxRetries(int maxRetries) Changes the maximum number of retries that will be performed when deadlocks are detected.
void	setNoWait(boolean noWait) Changes whether transactions will throw DbLockNotGrantedException instead of blocking when trying to access data that is locked by another transaction.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TransactionRunner

public TransactionRunner(DbEnv env)

Creates a transaction runner for a given Berkeley DB environment. The default maximum number of retries (10) will be used.

Parameters:

env - is the environment for running transactions.

TransactionRunner

public TransactionRunner(DbEnv env,
                         int maxRetries)

Creates a transaction runner for a given Berkeley DB environment and with a given number of maximum retries.

Parameters:

env - is the environment for running transactions.

maxRetries - is the maximum number of retries that will be performed when deadlocks are detected.

Method Detail

getMaxRetries

public int getMaxRetries()

Returns the maximum number of retries that will be performed when deadlocks are detected.

setMaxRetries

public void setMaxRetries(int maxRetries)

Changes the maximum number of retries that will be performed when deadlocks are detected. Calling this method does not impact transactions already running.

getDirtyRead

public boolean getDirtyRead()

Returns whether transactions will read data that is modified by another transaction but not committed.

setDirtyRead

public void setDirtyRead(boolean dirtyRead)

Changes whether transactions will read data that is modified by another transaction but not committed. Calling this method does not impact transaction already running.

getNoWait

public boolean getNoWait()

Returns whether transactions will throw DbLockNotGrantedException instead of blocking when trying to access data that is locked by another transaction.

setNoWait

public void setNoWait(boolean noWait)

Changes whether transactions will throw DbLockNotGrantedException instead of blocking when trying to access data that is locked by another transaction.

run

public void run(TransactionWorker worker)
         throws DbException,
                Exception

Calls the TransactionWorker.doWork() method and, for transactional environments, begins and ends a transaction. If the environment given is non-transactional, a transaction will not be used but the doWork() method will still be called.

In a transactional environment, a new transaction is started before calling doWork(). This will start a nested transaction if one is already active. If DbDeadlockException is thrown by doWork(), the transaction will be aborted and the process will be repeated up to the maximum number of retries specified. If another exception is thrown by doWork() or the maximum number of retries has occurred, the transaction will be aborted and the exception will be rethrown by this method. If no exception is thrown by doWork(), the transaction will be committed. This method will not attempt to commit or abort a transaction if it has already been committed or aborted by doWork().

Throws:

DbDeadlockException - when it is thrown by doWork() and the maximum number of retries has occurred. The transaction will have been aborted by this method.

Exception - when any other exception is thrown by doWork(). The exception will first be unwrapped by calling ExceptionUnwrapper.unwrap(java.lang.Exception). The transaction will have been aborted by this method.

DbException