Configuring DataSources in openejb.xml
The <Resource> element is used to configure a javax.sql.DataSource. It is also used to configure other resources like Timers, Topics, Queues. We will see some examples of using <Resource> to configure a DataSource.
The <Resource> element is designed after @Resource annotation and has similar attributes.
For example, this annotation in your bean:
@Resource(name = "myDerbyDatasource", type = javax.sql.DataSource.class)
Would map to a Resource declared in your openejb.xml as follows:
<Resource id="myDerbyDatasource" type="javax.sql.DataSource">
. . . .
<Resource>
Note that in the xml element, the type value of javax.sql.DataSource can abbreviated to just DataSource as follows:
<Resource id="myDerbyDatasource" type="DataSource">
. . . .
<Resource>
Configurations for some commonly used databases:
HSQLDB
The drivers are included with OpenEJB 3.0 and HSQLDB is the default database.
<Resource id="HSQLDB Database" type="DataSource">
JdbcDriver org.hsqldb.jdbcDriver
JdbcUrl jdbc:hsqldb:file:hsqldb
UserName sa
Password
</Resource>
Derby (Embedded)
<Resource id="Derby Database" type="DataSource">
#Embedded Derby example
JdbcDriver org.apache.derby.jdbc.EmbeddedDriver
JdbcUrl jdbc:derby:derbyDB;create=true
UserName admin
Password pass
</Resource>
MySQL
<Resource id="MySQL Database" type="DataSource">
# MySQL example
#
# This connector will not work until you download the driver at:
# http://www.mysql.com/downloads/api-jdbc-stable.html
JdbcDriver com.mysql.jdbc.Driver
JdbcUrl jdbc:mysql://localhost/test
UserName test
</Resource>
Oracle
<Resource id="Oracle Database" type="DataSource">
# Oracle example
#
# This connector will not work until you download the driver at:
# http://otn.oracle.com/software/tech/java/sqlj_jdbc/content.html
JdbcDriver com.mysql.jdbc.Driver
JdbcUrl jdbc:oracle:thin:@localhost:1521:orcl
UserName scott
Password tiger
</Resource>
PosgreSQL
<Resource id="PostgreSQL Database" type="DataSource">
# PostgreSQL example
#
# This connector will not work until you download the driver at:
# http://jdbc.postgresql.org/download.html
JdbcDriver org.postgresql.Driver
JdbcUrl jdbc:postgresql://localhost/test
UserName postgres
Password pass
</Resource>
InstantDB
<Resource id="InstantDB Database" type="DataSource">
# InstantDB example
#
JdbcDriver org.enhydra.instantdb.jdbc.idbDriver
JdbcUrl jdbc:idb:conf/instantdb.properties
UserName Admin
Password pass
</Resource>
JNDI names for configured DataSources
Example 1
<Resource id="Default JDBC Database" type="DataSource">
. . . . .
</Resource>
The global jndi name would be java:openejb/Resource/Default JDBC Database
Example 2
<Resource id="Derby Database" type="DataSource">
. . . . .
</Resource>
The global jndi name would be java:openejb/Resource/Derby Database
Obtaining a DataSource
DataSource references in your ejb should get automatically mapped to the Resource you declare. The shortest and easiest rule is that if your reference name matches a Resource in your openejb.xml, that's the one you get.
Alternatively, you can explicitly set them via an openejb-jar.xml.
There are various ways one could obtain a DataSource now. Lets take an example of Derby.
With a Resource declaration in your openejb.xml like this:
<Resource id="myDerbyDatabase" type="DataSource">
. . . . .
</Resource>
There are several possible ways to refer to it in your bean code or ejb-jar.xml
@Stateless
public class FooBean {
@Resource DataSource myDerbyDatase;
}
OR
@Stateless
public class FooBean {
@Resource(name="myDerbyDatabase")
DataSource dataSource;
}
OR
@Resource(name="myDerbyDatabase", type="javax.sql.DataSource")
@Stateless
public class FooBean {
public void setSessionContext(SessionContext sessionContext) {
DataSource dataSource = (DataSource) sessionContext.lookup("myDerbyDatabase");
}
public void someOtherMethod() throws Exception {
InitialContext initialContext = new InitialContext();
DataSource dataSource = (DataSource) initialContext.lookup("java:comp/env/myDerbyDatabase");
}
}
OR
<resource-ref>
<res-ref-name>myDerbyDatabase</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
</resource-ref>
OR
<resource-ref>
<res-ref-name>jdbc/myDerbyDatabase</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
</resource-ref>
OR
<resource-ref>
<res-ref-name>someOtherName</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<mapped-name>myDerbyDatabase</mapped-name>
</resource-ref>
