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Datasource independent access for storing and retrieving Objects from a persistent datasource.
Automates how objects and collections interacts with databases, datasources, and outside data.
An OADataSource is used to initialize, insert, update, delete and query Objects without using
datasource/database specific commands or query languages.
Includes support for distributed DataSources.
A datasource is any form of service that provides persistent storage and retrieval of data. The
most common datasource is for databases that use SQL and have a JDBC driver. Other types of storage
could be NoSQL, flat files, XML, streaming to other systems, application servers, web services, legacy
systems, object-relational engines, etc.
OADataSource subclasses self-register themselves with the static OADataSource. This static OADataSource
can then be used to find a OADataSource based on the Class of the Object that is being used.
Applications can be created that are independent of the datasource. At any time, a new OADataSource can be
used without affecting the existing application or objects.
Queries/Selects
The OADataSource Class offers the functionality to query a datasource based on the structure of
the Object structure and not on the Datasource structure. Results from a query are returned
in Objects instead of data or resultsets
Queries are based on using a form of Object Query Language. Property Paths are used to build "Where" and "Sort
Order" clauses.
A property path is a dot (".") separated list of property names that are used to navigate
from a root Class to a property value. To go from object to object, reference property names are used.
- All property names and connectors names are case insensitive.
- Can use the following connectors "AND", "&&", "||", "OR", "(", ")"
- Can use "=", "==", "!=", "<", "<=", ">", ">=", "LIKE", "%" (wildcard), "null" (any case)
- For convenience use OAConverter.toDataSourceString(value) to convert to String.
- For convenience use OAConverter.toDataSourceString(propertyName,value) to convert to a String that
will be expanded to be "propertyName =
- "ASC" ascending, "DESC" descending can be used with Order By properties.
When retrieving/selecting Objects from datasource, if the retrieved object is for an OAObject that
already exists in memory, the object in memory will be used instead of creating a duplicate object.
OASelect query object
The OASelect Class can be used for creating datasource independent Object Queries. OASelect manages
a query by working directly with a OADataSource. The Hub Collection Class uses OASelect
to perform its queries.
Note: OASelect is a convenience object and is not required for querying an OADataSource
(OADataSources can be used directly).
OADataSource has Pass-through methods, that can be used to run a native command on the datasource.
OADataSource can automatically create autonumber values for object identifier properties.
A GUID (Global Identifier) can also be included so that the assigned value is unique across multiple
datasources.
OADataSources can use log files to report all changes made to datasource.
Main Classes in this package
OADataSource is an abstract Class that defines a datasource independent interface for
data storage and retrieval. OADataSource manages all registered OADataSources.
OASelect works with OADataSource, used to build and manage datasource independent queries that
return Objects.
OAObject, Hub Collection and OADataSource
The OADataSource interface was created to offer OA the ability to persist and query objects, eliminating all
of the code that is usually required to work with a datasource/database. By establishing an
interface, the datasource is totally separated from the objects and application.
A makes it very easy to replace an existing OADataSource with a new one. For example, replace a
datasource that stored objects in a binary format (using object serialization), with a SQL Database. Or,
change database from one vendor to a different vendor.
OAObject automatically works with OADataSource for initializing new object, save(), delete(),
getObject(), getHub(), and validating property Id changes.
OAObject calls OADataSource.getDataSource(Class) to receive the OADataSource that is registered to manage a
particular its Class. This OAObject then uses this DataSource to initialize, save, delete.
Hub automatically works with OADataSources for select() queries, using the OASelect Class.