Entity from multiple tables

[microcz]

Hi everybody i am sorry for noob question, but I'm absolutely feckless.

I don't know how to create entity from two or more different database tables, joined on some of their foreign keys.

If there is no @Table annotation after @Entity annotation in java entity class, i receive exception, that database table which corresponds with entity cannot be found.
Also i haven't found any way how to join some entities using annotations and hql. @Entity with @NamedQuery doesn't work, when i wanna select from more than one table.
I was also wondering if it is possible to create entity for a database view, so i created view in my db and used seam to generate entity from it, it worked well and create @Table annotation with name of my db view as attribute name. But when i started my app it hasn't worked again, i received hibernate exception that table with such name cannot be found.

[thejavafreak]

You need to join / relate the property in one object using either @ManyToMany, @OneToOne, @OneToMany, or @ManyToOne as such:

@Entity
@Table(name="product")
public class Product{
   @ManyToOne private Category category; 
}

@Entity
@Table(name="category")
public class Category{
   @OneToMany private List<Product> products; 
}

Is this what you're looking for?

[microcz]

thank you very much for your reply, but not at all...  i want to make more complicated select.. in my app, i have these tables:

license
  licensepkid
  serialnumber
  otherdata

computer
  licensepkid
  otherdata

medium
  mediumpkid
  otherdata

licenseassignment
  assignpkid
  assigndate
  licensefkid
  computerfkid

mediuminstallation
  installpkid
  installdate
  mediumfkid
  computerfkid

returnedlicense (cant be used)
  returnpkid
  licensefkid

I used seam to generate entities for all these tables ...those with fkids are joined automatically  ...but what i wanna do is select all licenses (their serial numbers, date of assignment, medium on which they are) that has been installed but not returned ...so i wanna join licenseassignment with mediuminstallation on computerfkid somehow ...but i dunno what to do with resultlist is it possible to create entity bean for result of this query?

[microcz]

oh ...sorry ... posting again without formatting

thank you very much for your reply, but not at all... i want to make more complicated select.. in my app, i have these tables:

license
  license_pk_id
  serial_number
  other_data

computer
  license_pk_id
  other_data

medium
  medium_pk_id
  other_data

license_assignment
  assign_pk_id
  assign_date
  license_fk_id
  computer_fk_id

medium_installation
  install_pk_id
  install_date
  medium_fk_id
  computer_fk_id

returnedlicense (cant be used)
  return_pk_id
  license_fk_id

I used seam to generate entities for all these tables ...those with fk_ids are joined automatically ...but what i wanna do is select all licenses (their serial numbers, date of assignment, medium on which they are) that has been installed but not returned ...so i wanna join license_assignment with medium_installation on computer_fk_id somehow ...but i dunno what to do with resultlist is it possible to create entity bean for result of this query?

[perwik]

How about creating a view of the query in the database and mapping your Entity to that view?