Package com.webobjects.eoaccess

Provides the data access mechanisms for the Enterprise Objects technology.

See:
Description

Interface Summary

EOAdaptor.Delegate	This interface defines a delegate to EOAdaptor to handle specific requests that are normally handled by EOAdaptor (or rather its subclass since EOAdaptor is an abstract class).
EOAdaptorChannel.Delegate	EOAdaptorChannel invokes its delegate for nearly every operation that would affect data in the database server.
EOAdaptorContext.Delegate	EOAdaptorContext invokes its delegate any time a transaction is begun, committed, or rolled back.
EODatabaseContext.Delegate	This interface defines a delegate to EODatabaseContext to to handle specific requests that are ordinarily handled by EODatabaseContext.
EOModelGroup.ClassDelegate	This interface defines a delegate to the EOModelGroup class to allow modification of the creation of the default model group.
EOModelGroup.Delegate	This interface defines a delegate to EOModelGroup to allow instances to modify how the model group finds and loads models.
EOPropertyListEncoding	The EOPropertyListEncoding interface declares methods that read and write objects to property lists, which are dictionaries containing String, NSDictionary, NSArray, and NSData objects.
EOQualifierSQLGeneration	All qualifiers that can be used to generate SQL queries implement this interface.
EOSchemaGeneration	This interface has been introduced to define API for generating database schemas from EOModel files.
EOSchemaSynchronization	This interface has been introduced to define API to synchronize a database schema with a corresponding EOModel.
EOSchemaSynchronization.ColumnTypes	The ColumnTypes interface is only used when implementing schema synchronization API for a custom adaptor.
EOSQLExpression.SQLValue	This interface defines API for objects that can provide values for themselves to be used in SQL statements.
EOSynchronizationFactory.Delegate	The Delegate interface for EOSynchronizationFactory is restricted to use by the EOModeler application and should not be implemented by others.

Class Summary

EOAccessArrayFaultHandler	EOAccessArrayFaultHandler is a subclass of EOAccessGenericFaultHandler that implements a fault handler for an array of Enterprise Objects.
EOAccessFaultHandler	EOAccessFaultHandler is a subclass of EOAccessGenericFaultHandler that implements an object fault for Enterprise Objects.
EOAccessGenericFaultHandler	EOAccessGenericFaultHandler is an abstract class that helps an EOAccessFault to fire by fetching data using an EODatabaseContext.
EOAdaptor	An EOAdaptor represents a single connection to a database server.
EOAdaptorChannel	EOAdaptorChannel is an abstract class that provides its concrete subclasses with a structure for performing database operations.
EOAdaptorContext	EOAdaptorContext is an abstract class that provides its concrete subclasses with a structure for handling database transactions.
EOAdaptorOperation	An EOAdaptorOperation object represents a single primitive operation in a database server (lock, insert, update, or delete a particular row, or execute a stored procedure) as well as all the necessary information required to perform the operation.
EOAttribute	An EOAttribute represents a column, field, or property in a database and associates an internal name with an external name or expression by which the property is known to the database.
EODatabase	An EODatabase object represents a single database server.
EODatabaseChannel	An EODatabaseChannel represents an independent communication channel to the database server.
EODatabaseContext	EODatabaseContext is the basic EOObjectStore for the EOAccess Framework.
EODatabaseContext.DatabaseContextEvent	DatabaseContextEvent is a subclass of EOEvent, the parent class for objects that gather information, such as duration or order of execution, about various operations in WebObjects.
EODatabaseDataSource	EODatabaseDataSource is a concrete subclass of EODataSource, defined in EOControl.
EODatabaseOperation	An EODatabaseOperation object represents an operation (insert, update, or delete) to perform on an Enterprise Object and all the necessary information required to perform that operation.
EOEntity	An EOEntity describes a table in a database and associates a name internal to the Enterprise Objects Framework with an external name by which the table is known to the database.
EOEntityClassDescription	EOEntityClassDescription is a subclass of the control layer's EOClassDescription.
EOJoin	An EOJoin describes one source-destination attribute pair for an EORelationship.
EOModel	An EOModel represents a mapping between a database schema and a set of classes based on the entity-relationship model for an application.
EOModelGroup	An EOModelGroup represents an aggregation of related models.
EOProperty	EOProperty is an abstract class that embodies the notion of an object that belongs to (is the property of) an EOEntity.
EOQualifierSQLGeneration.Support	The abstract EOQualifierSQLGeneration.Support class provides basic functionality to subclasses that implement the EOQualifierSQLGeneration interface for specific qualifier types.
EORelationship	An EORelationship describes an association between two entities, based on attributes of those two entities.
EOSQLExpression	EOSQLExpression is an abstract superclass that defines how to build SQL statements for adaptor channels.
EOSQLExpressionFactory	EOSQLExpressionFactory builds SQL statements for adaptor channels.
EOSQLQualifier	Deprecated. The class EOSQLQualifier is deprecated.
EOStoredProcedure	EOStoredProcedure encapsulates the information stored in an EOModel about a stored procedure which is stored in a database server.
EOSynchronizationFactory	This class has been introduced to implement the interfaces EOSchemaGeneration and EOSchemaSynchronization, which were introduced in WebObjects 5.0.
EOUtilities	This class is a collection of convenience methods intended to make common operations with EOF easier.

Exception Summary

EOGeneralAdaptorException	A subclass of RuntimeException thrown by EOAccess.
EOObjectNotAvailableException	A subclass of RuntimeException thrown when EOAccess fails to retrieve an object, typically in response to a failed or empty fetch.
EOUtilities.MoreThanOneException	This exception is thrown from the methods in EOUtilities, indicating that multiple objects were found in a search that expected exactly one object as result.

Package com.webobjects.eoaccess Description

Provides the data access mechanisms for the Enterprise Objects technology.

Introduction

The EOAccess framework is one of a group of frameworks that make up the Enterprise Objects technology. The classes and interfaces that make up the EOAccess framework (also known as the access layer) allow your applications to interact with data stores (usually databases) at a high level of abstraction. The access layer is divided into two main parts:

• The database level, which allows applications to treat records as full-fledged enterprise objects.
• The adaptor level, which provides server-independent database access.

Working with the access layer allows you to have a finer level of control over database operations than just using the control layer.

The Adaptor Level

The adaptor level deals with database rows by packaging them as dictionaries. The adaptor level is primarily made up of the following classes:

• EOAdaptor is an abstract class that provides concrete subclasses with a structure for connecting to a database.
• EOAdaptorChannel is an abstract class that provides its concrete subclasses with a structure for performing database operations.
• EOAdaptorContext is an abstract class that defines transaction handling in applications that use the Enterprise Objects technology.
• EOAdaptorOperation is a class that represents a primitive operation in a database server and all the necessary information required by the operation.
• EOSQLExpression is an abstract superclass that defines how to build SQL statements for adaptor channels.

The Database Level

The database level is where enterprise objects are created from the dictionaries retrieved by the adaptor level. It's also where snapshotting is performed. The database level is primarily made up of the following classes:

• EODatabase is a class that represents a single database server.
• EODatabaseChannel is a class that represents an independent communication channel to the database server.
• EODatabaseContext is a subclass of EOObjectStore for accessing relational databases, and for creating and saving objects based on EOEntity definitions in an EOModel.
• EODatabaseOperation is a class that represents an operation--insert, update, or delete--to perform on an enterprise object and all the necessary information required to perform the operation.

The Modeling Classes

A model defines, in entity-relationship terms, the mapping between enterprise object classes and a database. The following are the principal modeling classes in the EOAccess framework:

• EOAttribute is a class that represents a column, field or property in a database, and associates an internal name with an external name or expression by which the property is known to the database.
• EOEntity is a class that describes a table in a database and associates a name internal to the framework with an external name by which the table is known to the database.
• EOJoin is a class that describes one source-destination attribute pair for an EORelationship.
• EOModel is a class that represents a mapping between a database schema and a set of classes based on the entity-relationship model.
• EOModelGroup is a class that represents an aggregation of related models.
• EORelationship is a class that describes an association between two entities, based on attributes of those two entities.
• EOStoredProcedure is a class that represents a stored procedure defined in a database, and associates a name internal to EOF with an external name known to the database.

Faulting

These classes implement or are used to implement object faulting:

• EOAccessArrayFaultHandler is a subclass of EOAccessGenericFaultHandler that implements a fault for an array of enterprise objects.
• EOAccessFaultHandler is a subclass of EOAccessGenericFaultHandler that implements an object fault for enterprise objects.
• EOAccessGenericFaultHandler is an abstract class that helps an EOAccessFault to fire by fetching data using an EODatabaseContext.

Extensions of EOControl Classes

The EOAccess framework also has a number of other useful classes, including:

• EODatabaseDataSource is a concrete subclass of EODataSource that fetches objects based on an EOModel, using an EODatabaseContext that services the data source's EOEditingContext.
• EOEntityClassDescription is a subclass of the control layer's EOClassDescription and extends the behavior of enterprise objects by deriving information about them from an associated EOModel.

Delegates

A number of EOAccess classes have delegates. The delegate methods are defined in these interfaces:

• An EOAdaptorChannel delegate receives messages for nearly every operation that would affect data in the database server, and it can preempt, modify, or track these operations.
• An EOAdaptorContext delegate receives messages for any transaction begin, commit, or rollback, and it can preempt, modify, or track these operations.
• An EOAdaptor delegate implements a method that can perform a database-specific transformations on a value.
• An EODatabaseContext delegate can intervene when objects are created and when they're fetched from the database.
• An EOModelGroup class delegate implements a method that returns the default model group.
• An EOModelGroup delegate influences how the model group finds and loads models.

Miscellaneous Classes and Interfaces

• EOUtilities is a collection of convenience methods intended to make common operations with the Enterprise Objects technology easier.
• EOPropertyListEncoding declares methods that read and write objects to property lists.