How to embed another entity in a Hibernate entity using its id?

Question

Say I have a Role type, which contains a long id, String name, etc. And I have another User class. Each user will have a roleId column which will point to Role.id.

In my database I will 2 tables, one for user, the other for role. The roleId in the user table will be a foreign key to role.id table.

My question is, how can I map this in Hibernate, so that I'll be able to have a Role role column in my User class, and would be able to do things like user.getRole().getName()?

Peter Bratton · Accepted Answer · 2014-02-26 14:28:37Z

2

From the manual:

Many-to-one associations are declared at the property level with the annotation @ManyToOne:

 @Entity
 public class User {
     @ManyToOne(cascade = {CascadeType.PERSIST, CascadeType.MERGE} )
     @JoinColumn(name="roleId")
     public Role getRole() {
         return role;
     }
     ...
 }

The @JoinColumn attribute is optional, the default value(s) is like in one to one, the concatenation of the name of the relationship in the owner side, _ (underscore), and the name of the primary key column in the owned side. In this example company_id because the property name is company and the column id of Company is id.

answered Feb 26, 2014 at 14:28

Peter Bratton

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6 Comments

Ali Over a year ago

in this case, where i have multiple roles, but each user will only have 1 role at a time, am i looking at ManyToOne or ManyToMany ?

Peter Bratton Over a year ago

@ManyToOne. You pretty much answered yourself :)

Ali Over a year ago

yeah, i realized that at the end but had typed the comment by then :). any chance you could look at this too: stackoverflow.com/questions/21971272/…

Peter Bratton Over a year ago

The answers there look good. Also check out the linked possible duplicate question.

Ali Over a year ago

Sorry, I linked to the wrong question. Here's what I had meant for you to look at: stackoverflow.com/questions/22042903/…

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Antoniossss · Accepted Answer · 2014-02-26 14:29:38Z

1

Simply declare yor fields as related entities so your User class would have private Role role field or limilar, annotated with proper @OneToX annotation.

answered Feb 26, 2014 at 14:29

Antoniossss

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