ProjectionList hibernate Criteria

[Sonx Nkuks]

Hi, am struggling to understand the use of Projections.property... consider the followin

public static void main(String[] args) {
	HibernateUtil.setup("create table Supplier ( id int, name VARCHAR);");
	HibernateUtil.setup("create table Product ( id int, name VARCHAR, description VARCHAR, price double,supplierId int);");
	
	prepareData();
	Session session = HibernateUtil.currentSession();
	
	Criteria crit = session.createCriteria(Product.class);
	ProjectionList projList = Projections.projectionList();
	projList.add(Projections.property("name"));
	projList.add(Projections.property("description"));
	crit.setProjection(projList);
	List results = crit.list();
	displayObjectsList(results);
	
	
	HibernateUtil.checkData("select * from Supplier");
	HibernateUtil.checkData("select * from Product");

}

What's the use of it here?

[Anantha Sharma]

Projections.property is used to retrieve specific columns from the datbase using the Criteria API...

ex:

public class Employee implements Serializable{
private Integer id,age;
private String name;
// getters & setters
}

to retrieve only the name & age of the employee i would say

Criteria c= //create criteria
ProjectionList list=Projections.projectionList();
list.add(Projections.property("name")); // this will ask hibernate to select name
list.add(Projections.property("age")); // this will ask hibernate to select age

c.setProjection(list); // this will link your field selection to the criteria
c.list() 
// this will generate a query like "select name,age from Employee"

if we run the criteria without the projectionlist added then we would get a query like select id, name, age from Employee.

Hope this helps.


- Anantha Sharma

[Sonx Nkuks]

Anantha Sharma wrote:Projections.property is used to retrieve specific columns from the datbase using the Criteria API...

ex:

public class Employee implements Serializable{
private Integer id,age;
private String name;
// getters & setters
}

to retrieve only the name & age of the employee i would say

Criteria c= //create criteria
ProjectionList list=Projections.projectionList();
list.add(Projections.property("name")); // this will ask hibernate to select name
list.add(Projections.property("age")); // this will ask hibernate to select age

c.setProjection(list); // this will link your field selection to the criteria
c.list() 
// this will generate a query like "select name,age from Employee"

if we run the criteria without the projectionlist added then we would get a query like select id, name, age from Employee.

Hope this helps.


- Anantha Sharma

Thanks Anantha