WebLogic: The Definitive Guide

EJB QL

EJB QL is the standard query language for defining the behavior of custom find and select methods. The EJB QL syntax is portable across databases, database schemas, and EJB containers because it is based on the abstract persistence schema defined for the entity beans and not the underlying data store. This allows you to specify the behavior of the query methods in an abstract, portable way. For each query method available to the entity bean, you must define a matching EJB QL statement that determines its runtime behavior.

WebLogic provides a number of extensions to the standard EJB QL. Some of these extensions also will be available in a future release of the EJB specification.

Using WebLogic Extensions to EJB QL

When using traditional EJB QL, you specify the EJB QL statement for each query method in the ejb-jar.xml descriptor file. However, if you intend to use any of the WebLogic extensions to EJB QL syntax, you also should define a weblogic-ql element in the weblogic-cmp-rdbms-jar.xml descriptor file. For instance, if you need to use the ORDERBY clause in your EJB QL statement, you must specify the EJB QL statement in the weblogic-cmp-rdbms-jar.xml file:

<!-- weblogic-cmp-rdbms-jar.xml entry -->
<weblogic-rdbms-bean>
        <ejb-name>EmployeeEJB</ejb-name>
        ...
        <weblogic-query>
                <query-method>
                        <method-name>findByLastName</method-name>
                        <method-params>
                                <method-param>java.lang.String</method-param>
                        </method-params>
                </query-method>
                <weblogic-ql>
                        <![CDATA[
                select object(e) from EmployeeEJB ...