web server - Borland Technical Publications

Connecting to JDBC Resources from J2EE Application Components
In this element you specify the following:
■
■
res-ref-name: this is the logical name for the resource, the same logical name you
use in the element of the standard ejb-jar.xml descriptor file. This is
the name your application components use to look up the datasource.
jndi-name: this is the JNDI name of the datasource that will be bound to its logical
name. It must match the value of the corresponding element of the
element deployed with the DAR.
■
cmp-resource: this is an optional boolean element that is relevant to entity beans
only. If set to True, the container's CMP engine will monitor this datasource.
Let's look at an example entity bean that uses the Oracle datasource we defined
above:
entity_bean
...
jdbc/MyDataSource
datasources/Oracle
True
...
As you can see, we used the identical JNDI name from the
element from the datasource definition. Now let's see how we obtain a datasource
object reference. To do so, the application performs a lookup of the
value of the deployed components and the object references are retrieved from the
remote CosNaming provider. For example:
javax.sql.DataSource ds1;
try {
javax.naming.Context ctx = (javax.naming.Context) new
javax.naming.InitialContext();
ds1 = (DataSource)ctx.lookup("java:comp/env/jdbc/MyDataSource");
}
catch (javax.naming.NamingException exp) {
exp.printStackTrace();
}
A database java.sql.Connection can now be obtained from ds1.
208 BES Developer’s Guide