Every select or finder method (except findByPrimaryKey) must have an EJB-QL query defined in the ejb-jar.xml file. The EJB-QL query is declared in a query element, which is contained in the entity element. The following are the declarations for findBadDudes_ejbql and ejbSelectBoss_ejbql queries:
<ejb-jar>
<enterprise-beans>
<entity>
<ejb-name>GangsterEJB</ejb-name>
<!-- ... -->
<query>
<query-method>
<method-name>findBadDudes_ejbql</method-name>
<method-params>
<method-param>int</method-param>
</method-params>
</query-method>
<ejb-ql><![CDATA[
SELECT OBJECT(g) FROM gangster g WHERE g.badness > ?1
]]></ejb-ql>
</query>
<query>
<query-method>
<method-name>ejbSelectBoss_ejbql</method-name>
<method-params>
<method-param>java.lang.String</method-param>
</method-params>
</query-method>
<ejb-ql><![CDATA[
SELECT DISTINCT underling.organization.theBoss FROM gangster underling WHERE underling.name = ?1 OR underling.nickName = ?1
]]></ejb-ql>
</query>
</entity>
</enterprise-beans>
</ejb-jar>
EJB-QL is similar to SQL but has some surprising differences. The following are some important things to note about EJB-QL:
EJB-QL is a typed language, meaning that it only allows comparison of like types (i.e., strings can only be compared with strings).
In an equals comparison a variable (single valued path) must be on the left hand side. Some examples follow:
g.hangout.state = 'CA' Legal 'CA' = g.shippingAddress.state NOT Legal 'CA' = 'CA' NOT Legal (r.amountPaid * .01) > 300 NOT Legal r.amountPaid > (300 / .01) Legal
Parameters use a base 1 index like java.sql.PreparedStatement.
Parameters are only allowed on the right hand side of a comparison. For example:
gangster.hangout.state = ?1 Legal ?1 = gangster.hangout.state NOT Legal