org.datanucleus.store.rdbms
Class AbstractSchemaTransaction

java.lang.Object
  org.datanucleus.store.rdbms.AbstractSchemaTransaction

Direct Known Subclasses:

DeleteTablesSchemaTransaction, ValidateTableSchemaTransaction

public abstract class AbstractSchemaTransaction
extends Object

An abstract base class for RDBMSManager transactions that perform some schema operation on the database.

Management transactions may be retried in the face of SQL exceptions to work around failures caused by transient conditions, such as DB deadlocks.

Field Summary

protected int	isolationLevel
protected int	maxRetries
protected org.datanucleus.store.connection.ManagedConnection	mconn
protected RDBMSStoreManager	rdbmsMgr

Constructor Summary

AbstractSchemaTransaction(RDBMSStoreManager rdbmsMgr, int isolationLevel)
Constructs a new management transaction having the given isolation level.

Method Summary

void	execute(org.datanucleus.ClassLoaderResolver clr) Executes the transaction.
protected Connection	getCurrentConnection() Obtains the current connection for the transaction.
protected abstract void	run(org.datanucleus.ClassLoaderResolver clr) Implements the body of the transaction.
abstract String	toString() Returns a description of the management transaction.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

rdbmsMgr

protected RDBMSStoreManager rdbmsMgr

isolationLevel

protected final int isolationLevel

maxRetries

protected final int maxRetries

mconn

protected org.datanucleus.store.connection.ManagedConnection mconn

Constructor Detail

AbstractSchemaTransaction

public AbstractSchemaTransaction(RDBMSStoreManager rdbmsMgr,
                                 int isolationLevel)

Constructs a new management transaction having the given isolation level.

Parameters:

rdbmsMgr - RDBMSManager to use

isolationLevel - One of the isolation level constants from java.sql.Connection.

Method Detail

toString

public abstract String toString()

Returns a description of the management transaction. Subclasses should override this method so that transaction failures are given an appropriate exception message.

Overrides:

toString in class Object

Returns:

A description of the management transaction.

run

protected abstract void run(org.datanucleus.ClassLoaderResolver clr)
                     throws SQLException

Implements the body of the transaction.

Parameters:

clr - the ClassLoaderResolver

Throws:

SQLException - Thrown if the transaction fails due to a database error that should allow the entire transaction to be retried.

getCurrentConnection

protected Connection getCurrentConnection()
                                   throws SQLException

Obtains the current connection for the transaction. Creates one if needed

Returns:

the connection

Throws:

SQLException

execute

public final void execute(org.datanucleus.ClassLoaderResolver clr)

Executes the transaction.

A database connection is acquired and the execute(ClassLoaderResolver)method is invoked. If the selected isolation level is not Connection.TRANSACTION_NONE, then commit() or rollback() is called on the connection according to whether the invocation succeeded or not. If the invocation failed the sequence is repeated, up to a maximum of maxRetries times, configurable by the system property datanucleus.store.maxRetries.

Parameters:

clr - the ClassLoaderResolver

Throws:

org.datanucleus.exceptions.NucleusDataStoreException - If a SQL exception occurred even after "maxRetries" attempts.