HQL - Parameters passing
Say at times we don't want to pass the actual value to the WHERE clause. Rather we would prefer to pass it as a parameter.
Query query = session.createQuery("from Employee employee WHERE employee.name= :nameParam");
query.setString("nameParam","Joe");
We will see in detail, how to achieve the above in Hibernate.
Let us take the Employee class :
Employee
class Employee {
int id;
String name;
-- getters and setters --
}
There should be a simple mapping file for the same :
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>
</class>
</hibernate-mapping>
Now, let us write the main() class and save three 'Employee' objects to database.
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();
Employee employeeJoe = new Employee();
employee.setId(1);
employee.setName("Joe");
Employee employeePeter = new Employee();
employee.setId(2);
employee.setName("Peter");
session.save(employeePeter);
Employee employeeChang = new Employee();
employee.setId(3);
employee.setName("Chang");
session.save(employeeChang);
session.getTransaction().commit();
session.close();
sessionFactory.close();
}
}
How to Parameterize values in WHERE clause?
Now, we will try to fetch some values from the 'EMPLOYEE' table using HQL SELECT and WHERE clause.
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.createQuery("from Employee employee WHERE employee.name= :nameParam");
query.setSring("nameParam","Joe");
session.getTransaction().commit();
session.close();
sessionFactory.close();
}
}
In the above SELECT we have not put the actual name (i.e. Joe) in the WHERE clause. Instead we have created a variable 'nameParam'
Query query = session.createQuery("from Employee employee WHERE employee.name= :nameParam");
and initialized it with 'Joe' in the 'query.setSring(...)' method.
query.setSring("nameParam","Joe");
