OpenEJB - Databases

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;
}

@Stateless
public class FooBean {
    @Resource(name="myDerbyDatabase")
    DataSource dataSource;
}

@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");
    }
}

<resource-ref>
   <res-ref-name>myDerbyDatabase</res-ref-name>
   <res-type>javax.sql.DataSource</res-type>
 </resource-ref>

<resource-ref>
   <res-ref-name>jdbc/myDerbyDatabase</res-ref-name>
   <res-type>javax.sql.DataSource</res-type>
 </resource-ref>

<resource-ref>
   <res-ref-name>someOtherName</res-ref-name>
   <res-type>javax.sql.DataSource</res-type>
   <mapped-name>myDerbyDatabase</mapped-name>
 </resource-ref>

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EJB 3.0

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