web server - Borland Technical Publications

Setting Properties
into a BLOB. The Container does not do any “smart” mapping on these classes or types;
it just stores the state in binary format. The Container's CMP engine observes the
following rule: the engine serializes as a BLOB all types that are not one of the explicitly
supported types.
In this context, the Container follows the JDBC specification: a BLOB is the type to which
LONGVARBINARY maps. (For Oracle, this is LONG RAW.)
Using SQL keywords
The CMP engine for the Borland Container can handle all SQL keywords that comply
with the SQL92 standard. However, you should keep in mind that vendors frequently
add their own keywords. For example, Oracle uses the keyword VARCHAR2. If you want
to ensure that the CMP engine can handle vendor keywords that may differ from the
SQL standard, set up an environment property in the deployment descriptor that maps
the CMP field name to the column name. By using this sort of environment property,
you do not have to modify your code.
For example, suppose you have a CMP field called “select”. You can use the following
environment property to map “select” to a column called “SLCT”, as shown below.
Data
select
SLCT
Using null values
It is possible that your database values can contain SQL null values. If so, you must
map them to fields whose Java data types are permitted to contain Java null values.
Typically, you do this by using Java types instead of primitive types. Thus, you use a
Java Integer type rather than a primitive int type, or a Java Float type rather than a
primitive float type.
Establishing a database connection
You must specify a DataSource so that the CMP engine can open a database
connection. The DataSource defines the information necessary for establishing a
database connection, such as username and password. Define a DataSource and then
use a resource-ref to refer to the DataSource in the XML deployment descriptor for the
bean. The CMP engine can then use the DataSource to access the database via
JDBC.
At the point in the vendor-specific XML file where you provide the jndi binding for the
resource-ref, add the element
True
For cases where the entity bean declares only one resource-ref, you do not need to
provide the above XML element. When the entity bean has only one resource-ref, the
Borland Container knows to automatically choose that one resource as the cmpresource.
Container-created tables
You can instruct the Borland EJB Container to automatically create tables for
container-managed entities based on the entity's container-managed fields. Because
table creation and data type mappings vary among vendors, you must specify the
JDBC database dialect in the deployment descriptor to the Container. For all
122 BES Developer’s Guide