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Documentation > WebObjects 4.5 >
EOAdaptor Reference
(informal interface)
Package:
com.apple.yellow.eoaccess
Interface Description
EOAdaptorChannel sends messages to its delegate for nearly
every operation that would affect data in the database server. The
delegate can use these methods to preempt these operations, modify
their results, or simply track activity.
Instance Methods
public abstract void adaptorChannelDidChangeResultSet(Object channel)
Invoked from
fetchRow when a
select operation resulted in multiple result sets. This method tells
the delegate that the next invocation of
fetchRow will fetch
from the next result set. This method is invoked when
fetchRow returns null and
there
are still result sets left to fetch. The delegate can invoke
setAttributesToFetch to
prepare for fetching the new rows.
public abstract void adaptorChannelDidEvaluateExpression(
Object channel,
EOSQLExpression expression)
Invoked from
evaluateExpression to
tell the delegate that a query language expression has been evaluated
by the database server.
public abstract void adaptorChannelDidExecuteStoredProcedure(
Object channel,
EOStoredProcedure procedure,
NSDictionary values)
Invoked from
executeStoredProcedure after
procedure is
executed successfully.
public abstract void adaptorChannelDidFetchRow(
Object channel,
NSMutableDictionary row)
Invoked from
fetchRow after a
row is fetched successfully. This method is not invoked if an exception occurs
during the fetch or if the same returns null because there are no
more rows in the current result set. The delegate may modify
row,
which will be returned from
fetchRow.
public abstract void adaptorChannelDidFinishFetching(Object channel)
Invoked from
fetchRow to tell
the delegate that fetching is finished for the current select operation.
This method is invoked when a fetch ends in
fetchRow because
there are no more result sets.
public abstract Throwable adaptorChannelDidPerformOperations(
Object channel,
NSArray operations,
Throwable exception)
Invoked from
performAdaptorOperations.
exception is null if
no exception was raised while
operations were
performed. Otherwise,
exception is
the raised exception. The delegate can return the same or a different
exception, which is re-raised by
performAdaptorOperations,
or it can return null to prevent the adaptor channel from raising
an exception.
public abstract void adaptorChannelDidSelectAttributes(
Object channel,
NSArray attributes,
com.apple.yellow.eocontrol.EOFetchSpecification fetchSpecification,
boolean flag,
EOEntity entity)
Invoked from
selectAttributes to
tell the delegate that rows have been selected in the database server.
public abstract NSDictionary adaptorChannelShouldConstructStoredProcedureReturnValues(Object channel)
Invoked from
returnValuesForLastStoredProcedureInvocation to
tell the delegate that
channel is constructing
return values for the last stored procedure evaluated. If the delegate
returns a value other than null, that value will be returned immediately
from
returnValuesForLastStoredProcedureInvocation.
public abstract boolean adaptorChannelShouldEvaluateExpression(
Object channel,
EOSQLExpression expression)
Invoked from
evaluateExpression to
tell the delegate that
channel is
sending an expression to the database server. The delegate returns true to
permit the adaptor channel to send
expression to
the server. If the delegate returns false, the adaptor channel does
not send the expression and returns immediately. When the delegate
returns false, the adaptor channel expects that the implementor
of the delegate has done the work that
evaluateExpression would
have done. The delegate can create a new EOSQLExpression and send
the expression itself before returning false.
public abstract NSDictionary adaptorChannelShouldExecuteStoredProcedure(
Object channel,
EOStoredProcedure procedure,
NSDictionary values)
Invoked from
executeStoredProcedure to tell the
delegate that
channel is executing
a stored procedure. If the delegate returns a value other than null,
that value is used as the arguments to the stored procedure instead
of
values.
public abstract NSDictionary adaptorChannelShouldReturnValuesForStoredProcedure(
Object channel,
NSDictionary returnValues)
Invoked from
returnValuesForLastStoredProcedureInvocation to
tell the delegate that
channel is returning
values for a stored procedure. If the delegate returns a value other
than null, that value is returned from
returnValuesForLastStoredProcedureInvocation instead
of
returnValues.
public abstract boolean adaptorChannelShouldSelectAttributes(
Object channel,
NSArray attributes,
com.apple.yellow.eocontrol.EOFetchSpecification fetchSpecification,
boolean flag,
EOEntity entity)
Invoked from
selectAttributes to
ask the delegate whether a select operation should be performed. The
delegate should not modify fetchSpecification. Instead, if the delegate
wants to perform a different select it should invoke
selectAttributes itself
with a new fetch specification, and return false (indicating that
the adaptor channel should not perform the select itself).
public abstract void adaptorChannelWillFetchRow(Object channel)
Invoked from
fetchRow to tell
the delegate that a single row will be fetched. The delegate can
determine the attributes used by the fetch by sending
attributesToFetch to
channel,
and can change the set of attributes to fetch by sending
setAttributesToFetch to
channel.
The adaptor channel performs the actual fetch.
public abstract NSArray adaptorChannelWillPerformOperations(
Object channel,
NSArray operations)
Invoked from
performAdaptorOperations to
tell the delegate that
channel is
performing the EOAdaptorOperations in
operations.
The delegate may return
operations or
a different NSArray for the adaptor channel to perform. If the delegate
returns null, the adaptor channel does not perform the operations
and returns from the method immediately.
