When you work with EGL, many of the details of data access
are in variables that you customize and then include in statements
such as add or delete. The customized variables include
details that are specific to a particular kind of data store, whether
the kind is a relational database; a file; or, in the future, some
other form of persistent storage. By including the kind-specific detail
in a variable rather than in the statement itself, the EGL design
allows most data-access statements to be structured in a particular
way, regardless of which kind of data store is accessed.
Most of the customized variables that you use for relational database
access are based on the following types:
- SQLDataSource, which represents a database connection.
- SQLResultSet, which represents a result set returned from an SQL
query.
- SQLStatement, which represents an SQL statement that is produced
by issuing the EGL Prepare statement. The SQL statement is
known as a prepared statement. It is structured from
a string at run time and often has a structure that is known only
at run time.
You can declare a variable of type SQLDataSource either to represent
a connection that is specified directly in your logic or to reference
a database binding in the EGL deployment descriptor:
- Here is an example in which the connection is specified directly
in the logic:
connectURL string = "jdbc:derby:SomeDB;create=true;";
properties Dictionary{user = "MyID", password = "MyPassword"};
ds SQLDataSource? = new SQLDataSource(connectURL, properties);
- Here is an example of a reference to an EGL deployment descriptor
entry named MyDatabaseBinding:
ds SQLDataSource?{@Resource{uri = "binding:MyDatabaseBinding"}};
Additional information is available: