EOAdaptorContext
Inherits from: NSObject
Package: com.apple.yellow.webobjects
Class Description
EOAdaptorContext is an abstract class that provides its concrete subclasses with a structure for handling database transactions. It's associated with EOAdaptor and EOAdaptorChannel, which, together with EOAdaptorContext, form the adaptor level of Enterprise Objects Framework's access layer. See the EOAdaptor class specification for more information about accessing, creating, and using adaptor level objects.
A concrete subclass of EOAdaptorContext provides database-specific method implementations and represents a single transaction scope (logical user) on the database server to which its EOAdaptor object is connected. You never interact with instances of the EOAdaptorContext class, rather your Enterprise Objects Framework applications use instances of concrete subclasses that are written to work with a specific database or other persistent storage system.
If a database server supports multiple concurrent transaction sessions, an adaptor context's EOAdaptor can have several contexts. When you use multiple EOAdaptorContexts for a single EOAdaptor, you can have several database server transactions in progress simultaneously. You should be aware of the issues involved in concurrent access if you do this.
EOAdaptorContext isn't declared to be abstract, but conceptually it is abstract. Never create instances of the EOAdaptorContext class. |
Method | Description |
beginTransaction | Begins a transaction in the database server. |
commitTransaction | Commits the last transaction begun. |
rollbackTransaction | Rolls back the last transaction begun. |
setDebugEnabled | Enables debugging in all the adaptor context's channels. |
Method Types
- Constructors
- EOAdaptorContext
- Accessing the adaptor
- adaptor
- Creating adaptor channels
- createAdaptorChannel
- channels
- Accessing and managing connection status
- hasOpenChannels
- hasBusyChannels
- handleDroppedConnection
- Controlling transactions
- beginTransaction
- commitTransaction
- rollbackTransaction
- transactionDidBegin
- transactionDidCommit
- transactionDidRollback
- hasOpenTransaction
- Accessing the delegate
- delegate
- setDelegate
- defaultDelegate
- setDefaultDelegate
Constructors
EOAdaptorContext
public EOAdaptorContext(EOAdaptor anAdaptor)
See Also: adaptor
Static Methods
debugEnabledDefault
public static boolean debugEnabledDefault()
defaultDelegate
public static Object defaultDelegate()
setDebugEnabledDefault
public static void setDebugEnabledDefault(boolean flag)
See Also: isDebugEnabled
setDefaultDelegate
public static void setDefaultDelegate(Object anObject)
Instance Methods
adaptor
public EOAdaptor adaptor()
See Also: EOAdaptorContext constructor
beginTransaction
public void beginTransaction()
The Enterprise Objects Framework automatically wraps database operations in transactions, so you don't have to begin and end transactions explicitly. In fact, letting the framework manage transactions is sometimes more efficient. You typically use beginTransaction only to execute more than one database operation in the same transaction scope.
This method invokes the delegate method adaptorContextShouldBegin before beginning the transaction. If the transaction is begun successfully, the method sends this a transactionDidBegin message and invokes the delegate method adaptorContextDidBegin. Throws an exception if the attempt is unsuccessful. Some possible reasons for failure are:
- A connection to the database hasn't been established.
- A transaction is already in progress.
- A fetch is in progress.
- The delegate refuses.
- The database server fails to begin a transaction.
An adaptor context subclass should override this method without invoking EOAdaptorContext's implementation.
See Also: hasOpenTransaction
channels
public NSArray channels()
See Also: createAdaptorChannel
commitTransaction
public void commitTransaction()
- A transaction is not in progress.
- Fetches are in progress.
- The delegate refuses.
- The database server fails to commit.
An adaptor context subclass should override this method without invoking EOAdaptorContext's implementation.
See Also: beginTransaction, rollbackTransaction, hasBusyChannels
createAdaptorChannel
public EOAdaptorChannel createAdaptorChannel()
See Also: channels
delegate
public Object delegate()
handleDroppedConnection
public void handleDroppedConnection()
You should never invoke this method; it is invoked automatically by the Framework. Subclasses must implement this method, without invoking super, if the adaptor supports automatic database reconnection.
hasBusyChannels
public boolean hasBusyChannels()
See Also: isFetchInProgress (EOAdaptorChannel)
hasOpenChannels
public boolean hasOpenChannels()
See Also: openChannel (EOAdaptorChannel), isOpen (EOAdaptorChannel)
hasOpenTransaction
public boolean hasOpenTransaction()
true
if
a transaction is open (begun but not yet committed or rolled back), false
otherwise.isDebugEnabled
public boolean isDebugEnabled()
See Also: debugEnabledDefault, setDebugEnabledDefault
rollbackTransaction
public void rollbackTransaction()
- A transaction is not in progress.
- Fetches are in progress.
- The delegate refuses.
- The database server fails to rollback.
An adaptor context subclass should override this method without invoking EOAdaptorContext's implementation.
See Also: beginTransaction, commitTransaction
setDebugEnabled
public void setDebugEnabled(boolean flag)
See Also: setDebugEnabled (EOAdaptorChannel), isDebugEnabled, setDebugEnabledDefault, channels
setDelegate
public void setDelegate(Object delegate)
See Also: channels
transactionDidBegin
public void transactionDidBegin()
You don't need to invoke this method unless you are implementing a concrete adaptor. Your concrete adaptor should invoke this method from within your adaptor context's implementation of beginTransaction method and anywhere else it begins a transaction-either implicitly or explicitly. For example, an adaptor channel's implementation of evaluateExpression should check to see if a transaction is in progress. If no transaction is in progress, it can start one explicitly by invoking beginTransaction. Alternatively, it can start an implicit transaction by invoking transactionDidBegin.
A subclass of EOAdaptorContext doesn't need to override this method. A subclass that does override it must incorporate the superclass's version through a message to super.
transactionDidCommit
public void transactionDidCommit()
You don't need to invoke this method unless you are implementing a concrete adaptor. Your concrete adaptor should invoke this method from within your adaptor context's implementation of commitTransaction method and anywhere else it commits a transaction-either implicitly or explicitly.
A subclass of EOAdaptorContext doesn't need to override this method. A subclass that does override it must incorporate the superclass's version through a message to super.
transactionDidRollback
public void transactionDidRollback()
You don't need to invoke this method unless you are implementing a concrete adaptor. Your concrete adaptor should invoke this method from within your adaptor context's implementation of rollbackTransaction method and anywhere else it rolls back a transaction-either implicitly or explicitly.
A subclass of EOAdaptorContext doesn't need to override this method. A subclass that does override it must incorporate the superclass's version through a message to super.
Notifications
AdaptorContextBeginTransactionNotification
public static final String AdaptorContextBeginTransactionNotification
Notification Object | The notifying EOAdaptorContext object |
Userinfo | None |
AdaptorContextCommitTransactionNotification
public static final String AdaptorContextCommitTransactionNotification
Notification Object | The notifying EOAdaptorContext object |
Userinfo | None |
AdaptorContextRollbackTransactionNotification
public static final String AdaptorContextRollbackTransactionNotification
Notification Object | The notifying EOAdaptorContext object |
Userinfo | None |