Add constraints to table with Hibernate.

[Arjun Abhishek]

If my assumption is correct, Hibernate is more on transactions and Data Manipulation and not in the Date Definition. I would like to know

How can i add constraints to table with Hibernate?
The two ways that strikes my mind is
a. In the setter method of the pojo class, add the constraint. But i need to know if this will work well in all the case.
b. using native sql, alter the table and add the constraint.

Please let me know which is correct way to add the constraint in the table.

thanks
Arjun.

[Cameron Wallace McKenzie]

Hibernate will create the constraints no problem. That's what it does.

Here are two classes, where a Team has many players, taken from my tutorial on mapping one to many relationships with Hibernate and JPA annotations.:

import javax.persistence.*;
@Entity
public class Player { 
 private long id;
 private String nickName;
 private Team team;

 @ManyToOne
 @JoinColumn(name="team_id")      
 public Team getTeam() {return team;}
 public void setTeam(Team t) {this.team = t;}
 @Id
 @GeneratedValue
 public long getId() {return id;}
 public void setId(long id) {this.id = id;}
 public String getNickName() {return nickName;}
 public void setNickName(String n) {nickName = n;}
}    

Now the other class:

 
import java.util.List; import javax.persistence.*;
@Entity
public class Team {
 private long id; 
 private String name;
 private List<Player> players; 

 @OneToMany(mappedBy="team",  
              targetEntity=Player.class, 
    fetch=FetchType.EAGER, cascade = CascadeType.ALL)
 public List<Player> getPlayers() {return players;}
 public void setPlayers(List<Player> p){players=p;}
 @Id
 @GeneratedValue
 public long getId() {return id;}
 public void setId(long id) {this.id = id;}
 public String getName() {return name;}
 public void setName(String name) {this.name = name;}
}   

Feeding this to Hibernate's SchemaExport class, you get the following SQL/DDL, which included the appropriate foreign key constraints.

CREATE TABLE  'examscam'.'player' 
('id' bigint(20) NOT NULL auto_increment, 
'nickName' varchar(255) default NULL, 
'team_id' bigint(20) default NULL, 
PRIMARY KEY  ('id'), 
KEY 'FK8EA387017289A91D' ('team_id'));

 
CREATE TABLE  'examscam'.'team'
 ( 'id' bigint(20) NOT NULL auto_increment, 
 'name' varchar(255) default NULL, 
 PRIMARY KEY  ('id'));    

Mapping Relationships and Creating Foreign Key Constraints with Hibernate and JPA

Hibernate is a full featured data framework. It's got all of the bells and whistles you need, and more.

-Cameron McKenzie

[Arjun Abhishek]

Thanks for the response.
But I was looking for something like this, say a constraint like Check. say to check age is between 1 and 100.

hibernate equivalent for the these statement.

Alter table Person
Add constraint ageCheck (age>= 1 and age <=100)

thanks
Karthick.

[Reehan Lalkhanwar]

If you are talking of CRUD, Hibernate's good as it works on concrete database tables mapped in the hbms as meta-data for Hibernate.
Modifying the DB would again involve modifying the hbm file.

[Cameron Wallace McKenzie]

There are a variety of annotations that impact how SQL is generated. Just some of the annotations for a Column are as follows:

The @Column Annotation

@Column(
  name="columnName"; 
    boolean unique() default false; 
      boolean nullable() default true; 
        boolean insertable() default true; 
          boolean updatable() default true; 
  String columnDefinition() default ""; 
    String table() default ""; 
       int length() default 255; 
          int precision() default 0; 
            int scale() default 0;
)
    

Now those are just JPA specific. Hibernate has extensions that go beyond the JPA specification as well. You'd have to research a bit deeper to find out how granular the types of constraints on columns and tables can be.

Kindest regards,

-Cameron McKenzie

[Arjun Abhishek]

Did you mean that I can add/represent constraint like check in the mappings of the entity.

thanks
Arjun.