public Connection getConnection() throws SQLException {
        try {
            InitialContext jndiCntx = new InitialContext();
            DataSource ds = (DataSource) jndiCntx.lookup("java:comp/env/ jdbc/myDataSource ");
            return ds.getConnection();
        } catch (NamingException ne) {
            throw new EJBException(ne);
        }
    }

<ejb-jar>
  <display-name>EJBM_MAIN</display-name>
  <enterprise-beans>
...
   <session>
      <ejb-name>MyEJBName</ejb-name>
      <home>...</home>
      <remote>...</remote>
      <local-home>...</local-home>
      <local>...</local>
      <ejb-class>...</ejb-class>
      <session-type>Stateless</session-type>
      <transaction-type>Container</transaction-type>
      <resource-ref>
        <res-ref-name> jdbc/myDataSource </res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
      </resource-ref>
    </session>
...
  </enterprise-beans>
  <assembly-descriptor>
...
    <container-transaction>
      <method>
        <ejb-name>MyEJBName</ejb-name>
        <method-name>*</method-name>
      </method>
      <trans-attribute>Required</trans-attribute>
    </container-transaction>
...
  </assembly-descriptor>