com.webobjects.eoaccess
Class EOAdaptorChannel

java.lang.Object
  com.webobjects.eoaccess.EOAdaptorChannel

Direct Known Subclasses:

JDBCChannel, JNDIChannel

public abstract class EOAdaptorChannel

extends Object

EOAdaptorChannel is an abstract class that provides its concrete subclasses with a structure for performing database operations. It is associated with EOAdaptor and EOAdaptorContext, which, together with EOAdaptorChannel, form the adaptor level of Enterprise Objects Framework's access layer.

Concrete subclasses of EOAdaptorChannel provide database-specific method implementations and represent an independent communication channel to the database server to which its EOAdaptor object is connected. You never interact with instances of the EOAdaptorChannel class, rather the Enterprise Objects Framework applications use instances of concrete subclasses that are written to interact with a specific database or other persistent storage system.

An EOAdaptorChannel represents an independent communication channel to the database server. Adaptor channels are used to manipulate rows (records) by selecting, fetching, inserting, updating, and deleting them. An EOAdaptorChannel also gives access to some of the meta-data on the server (which entities exist, and what their basic attributes or relationships are).

An EOAdaptorChannel works with an EOAdaptorContext object, which handles transactions. All of an EOAdaptorChannel's operations take place within the context of transactions controlled or tracked by the EOAdaptorContext. An EOAdaptorContext may manage several EOAdaptorChannels, but a channel is associated with only one context. Not all adaptors support multiple channels per context. See EOAdaptor and EOAdaptorContext documentation for more information.

Attribute Names

Any EOAdaptorChannel method that uses attribute names uses the internal names of the EOAttribute objects, not the external names in the database server. External names are only used privately by an adaptor channel and in the evaluateExpression method, which sends an expression directly to the server for processing.

Notifying the Adaptor Channel's Delegate

You can assign a delegate to an adaptor channel. The EOAdaptorChannel sends certain messages directly to the delegate, and the delegate responds to these messages on the channel's behalf. Many of the adaptor channel methods notify the channel's delegate before and after an operation is performed. Some delegate methods, such as adaptorChannelShouldEvaluateExpression, let the delegate determine whether the channel should perform an operation. Others, such as adaptorChannelDidEvaluateExpression, simply inform the delegate that an operation has occurred. The delegate has an opportunity to respond by implementing the delegate methods. If the delegate wants to intervene, it implements adaptorChannelShouldEvaluateExpression . If it simply wants notification when a transaction has begun, it implements adaptorChannelDidEvaluateExpression.

The principal attributes of the EOAdaptorChannel class are:

• Adaptor context
• Delegate

To create an instance of a concrete EOAdaptorChannel subclass, you send a createAdaptorChannel message to an instance of the corresponding EOAdaptorContext subclass. You rarely create adaptor channels yourself. They are generally created automatically by other framework objects.

The following table lists EOAdaptorChannel's more commonly-used methods:

Method	Description
openChannel	Opens the channel so it can perform database operations.
closeChannel	Close the channel.
selectAttributes	Selects rows matching the specified qualifier.
fetchRow	Fetches a row resulting from the last selectAttributes, executeStoredProcedure, or evaluateExpression.
insertRow	Inserts the specified row.
updateValuesInRowsDescribedByQualifier	Updates the row described by the specified qualifier.
deleteRowDescribedByQualifier	Deletes the row described by the specified qualifier.
executeStoredProcedure	Performs the specified stored procedure.
evaluateExpression	Sends the specified expression to the database.
performAdaptorOperation	Performs an adaptor operation by invoking the EOAdaptorChannel method appropriate for performing the specified operation.

Creating an EOAdaptorChannel Subclass

EOAdaptorChannel provides many default method implementations that are sufficient for concrete subclasses:

• adaptorContext
• delegate
• deleteRowDescribedByQualifier
• lockRowComparingAttributes
• performAdaptorOperation
• performAdaptorOperations
• updateValuesInRowDescribedByQualifier

The following methods establish structure and conventions that other Enterprise Objects Framework classes depend on and should be overridden with caution:

• setDelegate

If you override any of the above methods, the implementations should incorporate the superclass's implementation by calling super.

The remaining EOAdaptorChannel methods must be overridden by concrete subclasses in terms of the persistent storage system with which the adaptor channel interacts:

• attributesToFetch
• cancelFetch
• closeChannel
• deleteRowsDescribedByQualifier
• describeModelWithTableNames
• describeResults
• describeStoredProcedureNames
• describeTableNames
• evaluateExpression
• executeStoredProcedure
• fetchRow
• insertRow
• isFetchInProgress
• isOpen
• openChannel
• primaryKeyForNewRowWithEntity
• returnValuesForLastStoredProcedureInvocation
• selectAttributes
• setAttributesToFetch
• updateValuesInRowsDescribedByQualifier

Nested Class Summary

static interface

EOAdaptorChannel.Delegate EOAdaptorChannel invokes its delegate for nearly every operation that would affect data in the database server.

Field Summary

static String	AdaptorFailureKey A userInfo dictionary key.
static String	AdaptorOperationsKey A userInfo dictionary key.
static String	AdaptorOptimisticLockingFailure A userInfo dictionary key.
static String	FailedAdaptorOperationKey A userInfo dictionary key.

Constructor Summary

EOAdaptorChannel(EOAdaptorContext context)
Creates and returns an EOAdaptorChannel with the adaptor context context.

Method Summary

EOAdaptorContext	adaptorContext() Returns the receiver's EOAdaptorContext.
void	addStoredProceduresNamed(NSArray storedProcedureNames, EOModel model) The default implementation of this method does nothing.
abstract NSArray	attributesToFetch() An abstract method that should be implemented by subclasses to return the set of attributes to retrieve when fetchRow is next invoked.
abstract void	cancelFetch() An abstract method that should be implemented by subclasses to clear all result sets established by the last selectAttributes, executeStoredProcedure, or evaluateExpression message and terminate the current fetch, so that isFetchInProgress returns false.
abstract void	closeChannel() An abstract method that should be implemented by subclasses to close the EOAdaptorChannel so that it can't perform operations with the server.
Object	delegate() Returns the receiver's delegate, or null if the receiver doesn't have a delegate.
void	deleteRowDescribedByQualifier(EOQualifier qualifier, EOEntity entity) Deletes the row described by qualifier from the database table corresponding to entity.
abstract int	deleteRowsDescribedByQualifier(EOQualifier qualifier, EOEntity entity) An abstract method that should be implemented by subclasses to delete the rows described by qualifier from the database table corresponding to entity.
EOModel	describeModelWithTableNames(NSArray tableNames) The default implementation of this method returns null.
abstract NSArray	describeResults() An abstract method that should be implemented by subclasses to return an array of EOAttributes describing the properties available in the current result set, as determined by selectAttributes, executeStoredProcedure, or a statement evaluated by evaluateExpression.
NSArray	describeStoredProcedureNames() The default implementation of this method returns an empty array.
NSArray	describeTableNames() The default implementation of this method returns an empty array.
NSMutableDictionary	dictionaryWithObjectsForAttributes(Object[] objects, NSArray attributes) Used by EOAdaptorChannel subclasses to create dictionaries that can be returned from fetchRow.
abstract void	evaluateExpression(EOSQLExpression expression) An abstract method that should be implemented by subclasses to send expression to the database server for evaluation, beginning a transaction first and committing it after evaluation if a transaction isn't already in progress.
abstract void	executeStoredProcedure(EOStoredProcedure storedProcedure, NSDictionary values) An abstract method that should be implemented by subclasses to execute storedProcedure.
abstract NSMutableDictionary	fetchRow() An abstract method that should be implemented by subclasses to fetch the next row from the result set of the last selectAttributes, executeStoredProcedure, or evaluateExpression message sent to the receiver.
abstract void	insertRow(NSDictionary row, EOEntity entity) An abstract method that should be implemented by subclasses to insert the values of row into the table in the database that corresponds to entity.
abstract boolean	isFetchInProgress() An abstract method that should be implemented by subclasses to return true if the receiver is fetching, false otherwise.
abstract boolean	isOpen() An abstract method that should be implemented by subclasses to return true if the channel has been opened with openChannel, false if not.
void	lockRowComparingAttributes(NSArray atts, EOEntity entity, EOQualifier qualifier, NSDictionary snapshot) Attempts to lock a row in the database by selecting it with locking on.
abstract void	openChannel() An abstract method that should be implemented by subclasses to put the channel, and both its context and adaptor, into a state where they are ready to perform database operations.
void	performAdaptorOperation(EOAdaptorOperation adaptorOp) Performs adaptorOp by invoking the adaptor channel method appropriate for performing the specified operation.
void	performAdaptorOperations(NSArray adaptorOps) Performs adaptor operations by invoking performAdaptorOperation with each EOAdaptorOperation object in the array adaptorOps.
NSDictionary	primaryKeyForNewRowWithEntity(EOEntity entity) Deprecated. Use the plural version, primaryKeysForNewRowsWithEntity instead.
NSArray	primaryKeysForNewRowsWithEntity(int count, EOEntity entity) Returns an NSArray of primary key dictionaries for the number of new rows specified by count in the database table that corresponds to entity.
abstract NSDictionary	returnValuesForLastStoredProcedureInvocation() An abstract method that should be implemented by subclasses to return values from the execution of a stored procedure.
abstract void	selectAttributes(NSArray attributes, EOFetchSpecification fetchSpecification, boolean yn, EOEntity entity) An abstract method that should be implemented by subclasses to select attributes in rows matching the qualifier in fetchSpecification and set the receiver's attributes to fetch.
abstract void	setAttributesToFetch(NSArray attributes) An abstract method that should be implemented by subclasses to specify the set of attributes used to describe fetch data from a corresponding select.
void	setDelegate(Object delegate) Sets the receiver's delegate to delegate or removes its delegate if delegate is null.
void	updateValuesInRowDescribedByQualifier(NSDictionary row, EOQualifier qualifier, EOEntity entity) Updates the row described by qualifier with the new values in row.
abstract int	updateValuesInRowsDescribedByQualifier(NSDictionary row, EOQualifier qualifier, EOEntity entity) An abstract method that should be implemented by subclasses to update the rows described by qualifier with the values in row.

Methods inherited from class java.lang.Object

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

Field Detail

AdaptorFailureKey

public static final String AdaptorFailureKey

A userInfo dictionary key.

AdaptorOperationsKey

public static final String AdaptorOperationsKey

A userInfo dictionary key.

AdaptorOptimisticLockingFailure

public static final String AdaptorOptimisticLockingFailure

A userInfo dictionary key.

FailedAdaptorOperationKey

public static final String FailedAdaptorOperationKey

A userInfo dictionary key.

Constructor Detail

EOAdaptorChannel

public EOAdaptorChannel(EOAdaptorContext context)

Creates and returns an EOAdaptorChannel with the adaptor context context. Subclasses of EOAdaptorChannel should override this method.

You shouldn't invoke this method directly unless you are implementing a concrete adaptor context. It is invoked automatically from createAdaptorChannel, the EOAdaptorContext method used to create a new adaptor channel.

Parameters:

context - The EOAdaptorContext that controls transactions for the channel.

See Also:

EOAdaptorContext.createAdaptorChannel(), adaptorContext()

Method Detail

adaptorContext

public EOAdaptorContext adaptorContext()

Returns the receiver's EOAdaptorContext. Subclasses of EOAdaptorChannel don't need to override this method.

Returns:

The EOAdaptorContext that controls transactions for the channel.

See Also:

EOAdaptorChannel(EOAdaptorContext context)

addStoredProceduresNamed

public void addStoredProceduresNamed(NSArray storedProcedureNames,
                                     EOModel model)

The default implementation of this method does nothing. It can be overridden by subclasses to create EOStoredProcedure objects for the stored procedures named in storedProcedureNames and then to add them to model. Should throw a runtime exception if an error occurs.

This method is used in conjunction with describeStoredProcedureNames to build a default model in EOModeler.

Parameters:

storedProcedureNames - The names of stored procedures to add to a model.

model - The model to which to add stored procedures.

See Also:

describeStoredProcedureNames(), EOModel, EOStoredProcedure

attributesToFetch

public abstract NSArray attributesToFetch()

An abstract method that should be implemented by subclasses to return the set of attributes to retrieve when fetchRow is next invoked.

Returns:

Should return the array of attributes used by the adaptor for a particular fetch.

See Also:

fetchRow()

cancelFetch

public abstract void cancelFetch()

An abstract method that should be implemented by subclasses to clear all result sets established by the last selectAttributes, executeStoredProcedure, or evaluateExpression message and terminate the current fetch, so that isFetchInProgress returns false.

See Also:

selectAttributes(NSArray attributes, EOFetchSpecification fetchSpecification, boolean flag, EOEntity entity), executeStoredProcedure(EOStoredProcedure storedProcedure, NSDictionary values), evaluateExpression(EOSQLExpression expression), isFetchInProgress()

closeChannel

public abstract void closeChannel()

An abstract method that should be implemented by subclasses to close the EOAdaptorChannel so that it can't perform operations with the server. Any fetch in progress should be canceled.

If the receiver is the last open channel in an adaptor context and if the channel's adaptor context has outstanding transactions, closing the channel has server-dependent results: some database servers roll back all outstanding transactions but others do nothing. Regardless of whether outstanding transactions are rolled back, this method has the side effect of closing the receiver's adaptor context's connection with the database if the receiver is its adaptor context's last open channel.

See Also:

cancelFetch(), EOAdaptorContext.hasOpenTransaction()

delegate

public Object delegate()

Returns the receiver's delegate, or null if the receiver doesn't have a delegate. A subclass of EOAdaptorChannel doesn't need to override this method.

Returns:

The delegate of the adaptor channel.

deleteRowDescribedByQualifier

public void deleteRowDescribedByQualifier(EOQualifier qualifier,
                                          EOEntity entity)

Deletes the row described by qualifier from the database table corresponding to entity. Invokes deleteRowsDescribedByQualifier and throws an exception unless exactly one row is deleted. Subclasses of EOAdaptorChannel don't need to override this method.

Parameters:

qualifier - Describes the row to delete.

entity - The entity corresponding to the row to delete.

Throws:

EOGeneralAdaptorException - unless exactly one row is deleted.

See Also:

deleteRowsDescribedByQualifier( EOQualifier qualifier, EOEntity entity), EOEntity, EOQualifier

deleteRowsDescribedByQualifier

public abstract int deleteRowsDescribedByQualifier(EOQualifier qualifier,
                                                   EOEntity entity)

An abstract method that should be implemented by subclasses to delete the rows described by qualifier from the database table corresponding to entity. Should return the number of rows deleted. Should throw a runtime exception on failure. Some possible reasons for failure are:

• The adaptor channel isn't open.
• The adaptor channel is in an invalid state (for example, it's fetching).
• An error occurs in the database server.

Parameters:

qualifier - Describes the row(s) to delete.

entity - The entity corresponding to the row(s) to delete.

Returns:

Should return the number of rows deleted.

See Also:

deleteRowDescribedByQualifier(EOQualifier qualifier, EOEntity entity), isFetchInProgress(), EOAdaptorContext.hasOpenTransaction(), EOEntity, EOQualifier

describeModelWithTableNames

public EOModel describeModelWithTableNames(NSArray tableNames)

The default implementation of this method returns null. It can be overridden by subclasses to create and return a default model containing entities for the tables specified in tableNames and assign the adaptor name and connection dictionary to the new model. This method is typically used in conjunction with describeTableNames and describeStoredProcedureNames.

Parameters:

tableNames - The entity names for database tables.

Returns:

Should return a default model containing entities for the tables specified in tableNames.

See Also:

describeTableNames(), describeStoredProcedureNames(), EOModel

describeResults

public abstract NSArray describeResults()

An abstract method that should be implemented by subclasses to return an array of EOAttributes describing the properties available in the current result set, as determined by selectAttributes, executeStoredProcedure, or a statement evaluated by evaluateExpression. Only invoke this method if a fetch is in progress as determined by isFetchInProgress.

Returns:

Should return an array of attributes describing the properties available in the current result set.

See Also:

selectAttributes(NSArray attributes, EOFetchSpecification fetchSpecification, boolean flag, EOEntity entity), executeStoredProcedure(EOStoredProcedure storedProcedure, NSDictionary values), evaluateExpression(EOSQLExpression expression), isFetchInProgress(), EOAttribute

describeStoredProcedureNames

public NSArray describeStoredProcedureNames()

The default implementation of this method returns an empty array. It can be overridden by subclasses to read and return an array of stored procedure names from the database. Should throw a runtime exception if an error occurs.

This method is used in conjunction with addStoredProceduresNamed to build a default model in EOModeler.

Returns:

Should return an array of stored procedure names from the database.

See Also:

addStoredProceduresNamed( NSArray storedProcedureNames, EOModel model)

describeTableNames

public NSArray describeTableNames()

The default implementation of this method returns an empty array. It can be overridden by subclasses to read and return an array of table names from the database metadata.

This method is used in conjunction with describeStoredProcedureNames to build a default model in EOModeler.

Returns:

An array of table names from the database.

See Also:

describeModelWithTableNames(NSArray tableNames)

dictionaryWithObjectsForAttributes

public NSMutableDictionary dictionaryWithObjectsForAttributes(Object[] objects,
                                                              NSArray attributes)

Used by EOAdaptorChannel subclasses to create dictionaries that can be returned from fetchRow. You don't ordinarily invoke this method unless you are writing your own concrete adaptor. If you are writing a concrete adaptor, use of this method is optional but strongly recommended because it enables performance optimizations. The objects in objects are the values for the row that correspond to the EOAttribute objects in attributes.

A subclass of EOAdaptorChannel shouldn't override this method.

Parameters:

objects - Row values.

attributes - The corresponding row attributes.

Returns:

A dictionary to return from fetchRow.

See Also:

fetchRow(), EOAttribute

evaluateExpression

public abstract void evaluateExpression(EOSQLExpression expression)

An abstract method that should be implemented by subclasses to send expression to the database server for evaluation, beginning a transaction first and committing it after evaluation if a transaction isn't already in progress. Should throw a runtime exception if an error occurs. An adaptor channel uses this method to send SQL expressions to the database.

If expression results in a select operation being performed, you can fetch the results as you would if you had invoked selectAttributes. You must use the method setAttributesToFetch before you begin fetching. If expression evaluates to multiple result sets, you must invoke setAttributesToFetch before you begin fetching each subsequent set.

evaluateExpression invokes the delegate methods adaptorChannelShouldEvaluateExpression and adaptorChannelDidEvaluateExpression.

The upper layers of the Framework never invoke evaluateExpression directly. Thus, in adaptors for data stores that don't naturally support an expression language (for example, flat file adaptors), the implementation of this method doesn't need to do anything in order for the adaptor to work with the Framework.

Parameters:

expression - An expression to be evaluated by the database server.

See Also:

fetchRow(), selectAttributes( NSArray attributes, EOFetchSpecification fetchSpecification, boolean flag, EOEntity entity), setAttributesToFetch(NSArray attributes), EOAdaptorChannel.Delegate.adaptorChannelShouldEvaluateExpression( EOAdaptorChannel channel, EOSQLExpression expression), EOAdaptorChannel.Delegate.adaptorChannelDidEvaluateExpression( EOAdaptorChannel channel, EOSQLExpression expression), EOSQLExpression

executeStoredProcedure

public abstract void executeStoredProcedure(EOStoredProcedure storedProcedure,
                                            NSDictionary values)

An abstract method that should be implemented by subclasses to execute storedProcedure. Any arguments to the stored procedure are in values, a dictionary whose keys are the argument names. You should use fetchRow to get result rows and returnValuesForLastStoredProcedureInvocation to get return arguments and result status, if any. Should throw a runtime exception if an error occurs.

The upper layers of the Framework never invoke executeStoredProcedure directly. Thus, in adaptors for data stores that don't naturally support stored procedures, the implementation of this method doesn't need to do anything in order for the adaptor to work with the Framework.

Parameters:

storedProcedure - The stored procedure to execute.

values - A dictionary whose keys are the argument names and whose values are the argument values to be passed to storedProcedure.

See Also:

returnValuesForLastStoredProcedureInvocation(), fetchRow(), (EOStoredProcedure storedProcedure, NSDictionary values), EOStoredProcedure

fetchRow

public abstract NSMutableDictionary fetchRow()

An abstract method that should be implemented by subclasses to fetch the next row from the result set of the last selectAttributes, executeStoredProcedure, or evaluateExpression message sent to the receiver. Should return values for the receiver's attributesToFetch in a dictionary whose keys are the attribute names. When there are no more rows in the current result set, this method should return null and invoke the delegate method adaptorChannelDidChangeResultSet if there are more results sets.

When there are no more rows or result sets, this method should return null, end the fetch, and invoke adaptorChannelDidFinishFetching. isFetchInProgress returns true until the fetch is canceled or until this method exhausts all result sets and returns null.

This method should also invoke the delegate methods adaptorChannelWillFetchRow and adaptorChannelDidFetchRow. Should throw a runtime exception if an error occurs.

Returns:

Should return values for the receiver's attributesToFetch in a dictionary whose keys are the attribute names.

See Also:

executeStoredProcedure(EOStoredProcedure storedProcedure, NSDictionary values), selectAttributes(NSArray attributes, EOFetchSpecification fetchSpecification, boolean flag, EOEntity entity), evaluateExpression(EOSQLExpression expression), attributesToFetch(), (EOAdaptorChannel channel), EOAdaptorChannel.Delegate.adaptorChannelDidFinishFetching( EOAdaptorChannel channel), EOAdaptorChannel.Delegate.adaptorChannelWillFetchRow( EOAdaptorChannel channel), EOAdaptorChannel.Delegate.adaptorChannelDidFetchRow(EOAdaptorChannel channel , NSMutableDictionary row), setAttributesToFetch(NSArray attributes)

insertRow

public abstract void insertRow(NSDictionary row,
                               EOEntity entity)

An abstract method that should be implemented by subclasses to insert the values of row into the table in the database that corresponds to entity. row is a dictionary whose keys are attribute names and whose values are the values to insert. Row keys must refer to attributes that all belong to entity and that are either non- flattened or all flattened through the same relationship path. Should throw a runtime exception on failure. Some possible reasons for failure are:

• The user logged in to the database doesn't have permission to insert a new row.
• The adaptor channel is in an invalid state (for example, fetching).
• The row fails to satisfy a constraint defined in the database server.

Parameters:

row - An NSDictionary whose keys are attribute names and whose values are the values that will be inserted.

entity - The entity that corresponds to row.

See Also:

EOEntity

isFetchInProgress

public abstract boolean isFetchInProgress()

An abstract method that should be implemented by subclasses to return true if the receiver is fetching, false otherwise. An adaptor channel is fetching if:

• It has successfully invoked selectAttributes.
• A stored procedure that returns rows has been successfully executed using executeStoredProcedure.
• An expression sent through evaluateExpression resulted in a select operation being performed.

An adaptor channel stops fetching when there are no more records to fetch or when cancelFetch is invoked.

Returns:

Should return true if the receiver is fetching, else false.

See Also:

fetchRow(), evaluateExpression(EOSQLExpression expression), selectAttributes(NSArray attributes, EOFetchSpecification fetchSpecification, boolean flag, EOEntity entity), executeStoredProcedure(EOStoredProcedure storedProcedure, NSDictionary values)

isOpen

public abstract boolean isOpen()

An abstract method that should be implemented by subclasses to return true if the channel has been opened with openChannel, false if not.

Returns:

Should return true if the channel has been opened with openChannel().

See Also:

openChannel(), closeChannel()

lockRowComparingAttributes

public void lockRowComparingAttributes(NSArray atts,
                                       EOEntity entity,
                                       EOQualifier qualifier,
                                       NSDictionary snapshot)

Attempts to lock a row in the database by selecting it with locking on. The lock operation succeeds if a select statement generated with qualifier retrieves exactly one row and the values in the row match the values in snapshot, a dictionary whose keys are attribute names and whose values are the values that were last fetched from the database.

lockRowComparingAttributes invokes selectAttributes with atts as the attributes to select, a fetch specification built from qualifier, locking on, and entity as the entity. If the select returns no rows or more than one row, the method throws an exception. It also throws an exception if the values in the returned row don't match the corresponding values in snapshot.

The Framework uses this method whenever it needs to lock a row. When the Framework invokes it, qualifier specifies the primary key of the row to be locked and attributes used for locking to be compared in the database server. If any of the values specified in qualifier are different than the values in the database row, the select operation will not retrieve or lock the row. When this happens, the row to be locked has been updated in the database since it was last retrieved, and it isn't safe to update it.

Some attributes (such as BLOB types) can't be compared in the database. atts should specify any such attributes. (If the row doesn't contain any such attributes, atts can be null.) If qualifier generates a select statement that returns and locks a single row, this method performs an in-memory comparison between the value in the retrieved row and the value in snapshot for each attribute in atts. Therefore, snapshot must contain an entry for each attribute in atts. In addition, it must contain an entry for the row's primary key.

Subclasses of EOAdaptorChannel don't need to override this method.

Parameters:

atts - An array containing all values that need to be fetched and compared in memory, for example, BLOB columns in the database; can be null if the row does not contain any BLOBs.

entity - The entity that corresponds to the row being locked.

qualifier - The primary key of the row to be locked and attributes used for locking to be compared in the database server.

snapshot - A dictionary whose keys are attribute names and whose values are the values that were last fetched from the database.

Throws:

EOGeneralAdaptorException - if the select returns no rows or more than one row.

See Also:

selectAttributes(NSArray attributes, EOFetchSpecification fetchSpecification, boolean flag, EOEntity entity), EODatabaseContext, EOEntity, EOQualifier

openChannel

public abstract void openChannel()

An abstract method that should be implemented by subclasses to put the channel, and both its context and adaptor, into a state where they are ready to perform database operations. Should throw a runtime exception if an error occurs.

See Also:

isOpen(), closeChannel()

performAdaptorOperation

public void performAdaptorOperation(EOAdaptorOperation adaptorOp)

Performs adaptorOp by invoking the adaptor channel method appropriate for performing the specified operation. For example, if the adaptor operator for adaptorOp is EOAdaptorInsertOperator, this method invokes insertRow using information in adaptorOp to supply the arguments. Throws an exception if an error occurs.

A subclass of EOAdaptorChannel doesn't need to override this method.

Parameters:

adaptorOp - An adaptor operation to perform.

Throws:

EOGeneralAdaptorException - if an error occurs.

See Also:

insertRow(NSDictionary row, EOEntity entity), performAdaptorOperations(NSArray adaptorOps)

performAdaptorOperations

public void performAdaptorOperations(NSArray adaptorOps)

Performs adaptor operations by invoking performAdaptorOperation with each EOAdaptorOperation object in the array adaptorOps. An adaptor channel subclass may be able to override this method to take advantage of database-specific batch processing capabilities. Invokes the delegate methods adaptorChannelWillPerformOperations and adaptorChannelDidPerformOperations.

This method throws a runtime exception if an error occurs; the exception's userInfo dictionary provides details about the error. The exception's userInfo dictionary contains these keys:

Constant	The corresponding value in the exception's userInfo dictionary
AdaptorOperationsKey	An array of the EOAdaptorOperations being executed.
FailedAdaptorOperationKey	The particular EOAdaptorOperation that failed.
AdaptorFailureKey	If present, offers additional information on the type of error that occurred. Currently, the only possible value for this key is AdaptorOptimisticLockingFailure, which indicates that an update or lock operation failed because the row found in the database did not match the snapshot taken when the row was last fetched into the application.

Subclasses of EOAdaptorChannel don't need to override this method.

Parameters:

adaptorOps - An array of EOAdaptorOperation objects.

See Also:

FailedAdaptorOperationKey, EOAdaptorChannel.Delegate.adaptorChannelDidPerformOperations( EOAdaptorChannel channel, NSArray operation, Throwable exception), EOAdaptorChannel.Delegate.adaptorChannelWillPerformOperations( EOAdaptorChannel channel, NSArray operations), EODatabaseContext

primaryKeyForNewRowWithEntity

public NSDictionary primaryKeyForNewRowWithEntity(EOEntity entity)

Deprecated. Use the plural version, primaryKeysForNewRowsWithEntity instead.

See Also:

primaryKeysForNewRowsWithEntity(int count, EOEntity entity)

primaryKeysForNewRowsWithEntity

public NSArray primaryKeysForNewRowsWithEntity(int count,
                                               EOEntity entity)

Returns an NSArray of primary key dictionaries for the number of new rows specified by count in the database table that corresponds to entity. The primary keys returned from this method are dictionaries whose keys are the primary key attribute names. For example, suppose you've got a table MOVIE with primary key MOVIE_ID, and the corresponding Movie entity's primary key attribute is movieID. In this scenario, each dictionary in the NSArray returned from this method has one entry whose key is movieID and whose value is the unique value to assign.

If the primary key is compound (made up of more than one attribute), the dictionary should contain an entry for each primary key attribute. Note, however, that the Enterprise Objects Frameworks adaptors don't handle compound primary keys; they return null if the primary key is compound.

Parameters:

count - The number of new rows for which to generate primary keys.

entity - The entity for which to assign primary keys.

Returns:

An array of dictionaries whose keys are the primary key attribute names, or null if the adaptor is unable to provide the primary key values.

See Also:

EOEntity

returnValuesForLastStoredProcedureInvocation

public abstract NSDictionary returnValuesForLastStoredProcedureInvocation()

An abstract method that should be implemented by subclasses to return values from the execution of a stored procedure. Used in conjunction with executeStoredProcedure. The dictionary returned by this method should have entries whose keys are the names of the stored procedure's parameters and whose values are the parameter values. The dictionary also should contain a special entry for the stored procedure's return value with the key "returnValue".

Should return an empty dictionary for stored procedures that have void return types. Should return null if the stored procedure has results to fetch. In this case, you must use fetchRow until there are no more results to fetch before the return value will be available.

Returns:

Should return a dictionary of the stored procedure's parameter names and values, and its return value.

See Also:

executeStoredProcedure(EOStoredProcedure storedProcedure, NSDictionary values), fetchRow(), EOStoredProcedure

selectAttributes

public abstract void selectAttributes(NSArray attributes,
                                      EOFetchSpecification fetchSpecification,
                                      boolean yn,
                                      EOEntity entity)

An abstract method that should be implemented by subclasses to select attributes in rows matching the qualifier in fetchSpecification and set the receiver's attributes to fetch. The selected rows compose one or more result sets, each row of which should be returned by subsequent fetchRow calls according to fetchSpecification's sort orderings. If the yn flag is true, the rows should be locked if possible so that no other user can modify them. The lock specification in fetchSpecification should be ignored. Should throw a runtime exception if an error occurs. Some possible reasons for failure are:

• The adaptor channel is in an invalid state (for example, fetching).
• The database failed to lock the specified rows.

Parameters:

attributes - An array of the attributes to select.

fetchSpecification - Describes the row(s) to select.

yn - true if rows should be locked.

entity - The entity corresponding to the row(s) to be selected.

See Also:

fetchRow(), EOEntity, EOFetchSpecification, EOSortOrdering

setAttributesToFetch

public abstract void setAttributesToFetch(NSArray attributes)

An abstract method that should be implemented by subclasses to specify the set of attributes used to describe fetch data from a corresponding select. attribute is an array of the attributes to fetch. This method should be invoked after evaluateExpression but before the first call to fetchRow. This method should throw a runtime exception if invoked when there is no fetch in progress.

Parameters:

attributes - An array of the attributes to fetch.

See Also:

selectAttributes( NSArray attributes, EOFetchSpecification fetchSpecification, boolean flag, EOEntity entity), evaluateExpression(EOSQLExpression expression), fetchRow()

setDelegate

public void setDelegate(Object delegate)

Sets the receiver's delegate to delegate or removes its delegate if delegate is null. A subclass of EOAdaptorChannel doesn't need to override this method. A subclass that does override it must incorporate the superclass's version through a message to super.

Parameters:

delegate - The delegate to set for the receiver.

updateValuesInRowDescribedByQualifier

public void updateValuesInRowDescribedByQualifier(NSDictionary row,
                                                  EOQualifier qualifier,
                                                  EOEntity entity)

Updates the row described by qualifier with the new values in row. Invokes updateValuesInRowsDescribedByQualifier and throws an exception unless exactly one row is updated. A subclass of EOAdaptorChannel doesn't need to override this method.

Parameters:

row - New values for a row.

qualifier - Describes the row to update.

entity - The entity corresponding to the row to update.

Throws:

EOGeneralAdaptorException - unless exactly one row is updated.

See Also:

updateValuesInRowsDescribedByQualifier( NSDictionary values, EOQualifier qualifier, EOEntity entity), EOEntity, EOQualifier

updateValuesInRowsDescribedByQualifier

public abstract int updateValuesInRowsDescribedByQualifier(NSDictionary row,
                                                           EOQualifier qualifier,
                                                           EOEntity entity)

An abstract method that should be implemented by subclasses to update the rows described by qualifier with the values in row. row is a dictionary whose keys are attribute names and whose values are the new values for those attributes (the dictionary need only contain entries for the attributes being changed). Should return the number of updated rows. Should throw a runtime exception if an error occurs. Some possible reasons for failure are:

• The user logged in to the database doesn't have permission to update.
• The adaptor channel is in an invalid state (for example, fetching).
• The new values fail to satisfy a constraint defined in the database server.

Parameters:

row - The new values for row(s).

qualifier - Describes row(s) to update.

entity - The entity corresponding to the row(s) to update.

Returns:

Should return the number of updated rows.

See Also:

(NSDictionary row, EOQualifier qualifier, EOEntity entity), EOEntity, EOQualifier