HQL - Named Queries

Say at times we do not want to keep the queries in our main code.

Query query = session.createQuery("from Employee employee WHERE employee.name= 'Joe'");

and replace "from Employee employee WHERE employee.name= 'Joe'" with a variable.

Luckily it can be achieved using 'Named Queries'.

So, we assume that the 'EMPLOYEE' table is already loaded.

EMPLOYEE

ID	NAME
1	Joe
2	Peter
3	Chang

Where to write the Named Query?

The actual query can be written in the mapping file.

Employee.hbm.xml

<?xml version = "1.0" encoding = "utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
<class name = "Employee" table = "EMPLOYEE">
<id name = "id" type = "string">
<column name = "ID">
</id>
<property name = "name" type = "string">
<column name = "NAME">
</property>

<query name="empName">
<![CDATA[from Employee employee WHERE employee.name= 'Joe']]>
</query>

</class>
</hibernate-mapping>

So, we have written the query in the mapping file inside '<query>' tag

in a particular format

<![CDATA[from Employee employee WHERE employee.name= 'Joe']]>

Now, let us write the main() class :

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateSave {
public static void main(String[] args) {

static SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
Session session = sessionFactory.openSession();
session.beginTransaction();

Query query = session.getNamedQuery("empName");

session.getTransaction().commit();

session.close();
sessionFactory.close();
}
}

So instead of writing

session.createQuery(...);

We have used

Query query = session.getNamedQuery("empName");

Which takes the query from the mapping file by matching 'empName'

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