Scattered HQL string literals in Java code are hard to maintain and look ugly. To avoid it, Hibernate come out a technique called “names queries”, it lets developer to put all HQL into the XML mapping file or via annotation.
XML mapping file:
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.dto.EmployeeDTO" table="EMPLOYEES">
<id name="id" column="ID"><generator class="assigned"/></id>
<property name="empId" column="EMP_ID" />
<property name="empFirstName" column="EMP_FIRST_NAME" />
<property name="empLastName" column="EMP_LAST_NAME" />
<property name="createdOn" column="CREATED_ON"/>
</class>
<!-- Native SQL in named query -->
<sql-query name="updateEmployee">
<![CDATA[
UPDATE EMPLOYEES SET EMP_LAST_NAME=:empLastName WHERE EMP_ID=:employeeId
]]>
</sql-query>
<!-- HQL in named query -->
<query name="findEmpById">
<![CDATA[from EmployeeDTO e where e.empId = :employeeId]]>
</query>
</hibernate-mapping>
HQL and Native SQL in annotation
<!-- HQL in named query -->
@NamedQueries({
@NamedQuery(
name = "updateEmployee",
query = "from EmployeeDTO e where e.empId = :employeeId"
)
})
<!-- Native SQL in named query -->
@NamedNativeQueries({
@NamedNativeQuery(
name = "updateEmployee",
query = "UPDATE EMPLOYEES SET EMP_LAST_NAME=:empLastName WHERE EMP_ID=:employeeId",
resultClass = EmployeeDTO.class
)
})
@Entity
@Table(name = "EMPLOYEES")
public class EmployeeDTO implements java.io.Serializable {
...
}
Java Code to use the named Query:
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;
public class HibernateNamedQuery extends HibernateDaoSupport {
public int updateEmployee(String p_employeeId, String p_modifiedBy) {
Session session = null;
try {
session = getHibernateTemplate().getSessionFactory().openSession();
Query query = session.getNamedQuery("updateEmployee");
query = query.setString("empLastName", "Kumar");
int rowsUpdated = query.executeUpdate();
return rowsUpdated;
} finally {
releaseSession(session);
}
}
public List<Object[]> fetchEmployeeDetails(String empId) {
Session session = null;
try {
session = getHibernateTemplate().getSessionFactory().openSession();
Query query = session.getNamedQuery("findEmpById");
query = query.setString("employeeId",empId);
return query.list();
} finally {
releaseSession(session);
}
}
}
