Question

Hibernate - fetch from more than one table

Asked by: radhnki

Hi,
   I have a table and 2 of its column are the reference to another 2 tables (foreign key-primary key relation). in hibernate, i know i can use many to one relation ship to fetch the value. But is it possible to use more than one many-to-one mapping for a  same class?
i am using struts2 hibernate3 and mysql.

-Rk

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Asked On
2009-11-01 at 21:57:56ID24862866
Topics

Jakarta Struts

,

WebApplications

Participating Experts
2
Points
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Answers

 

by: ozlevanonPosted on 2009-11-02 at 00:27:42ID: 25717750

Yes, you can do that. I don't know of any limit on the number of Many To One members in a class, see an example below.
In the code below, when you retrieve a Person object, it will be retrieved with the city and country already read from the database.

import javax.persistence.*; 
@Entity
@Table(name = "Person")
public class Person
{
	@Id
	@Column(name = "PERSON_ID")
	@GeneratedValue(strategy = GenerationType.AUTO)
	private Integer id = null;
	
	private String name = null;
	private String address = null; 
	@ManyToOne
	@JoinColumn(name = "CITY_ID")
	private City advertiser = null; 
	@ManyToOne
	@JoinColumn(name = "COUNTRY_ID")
	private Country country = null;
}

                                              
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by: radhnkiPosted on 2009-11-05 at 22:31:29ID: 25757011

Hi,
   any other inputs?
my requirement is, i have a employe table with 2 colums, one is project another one is Manager
where project and manger are 2 different tables. with primary key mapped to employee table project and manager column.

Now i want to know how can i join these 3 tables in a single hql query, so that i can get all the values,.

Rk

 

by: josephtsangPosted on 2009-12-04 at 00:10:35ID: 25969843

My suggested HQL:

from Employee e
join fetch e.manager
join fetch e.project
where ......

20120131-EE-VQP-002

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