what is POJO entity ?

[alfred jones]

I found this code in tutorial for EJB 3.0 entities.

@Entity
@Table(name="bookbank")
public class BookBank implements Serializable {
long id;
String title;
String author;
double price;


what is "bookbank"? is it the database table name ?

[Prabhakar Reddy Bokka]

Yes. It is database table name.

[alfred jones]

Prabhakar Reddy Bokka wrote:Yes. It is database table name.

I have table name as tbl_book_bank ..... I'm worried because my table name has underscore _ symbol....... is it allowed ?



How do you put primary key and foreign key in entity class ? Is it required or container will do this for me ?

[Tim McGuire]

alfred jones wrote:

I have table name as tbl_book_bank ..... I'm worried because my table name has underscore _ symbol....... is it allowed ?

It is allowed. All my tables have them.

[Tim McGuire]

alfred jones wrote:
How do you put primary key and foreign key in entity class ? Is it required or container will do this for me ?

you need to specify primary key with an Id annotation:

@Id
@Column(name="some_name")
public Long getUserId(){
    ....
}

read all about how to do foriegn keys here under the mapping headings :
http://docs.oracle.com/cd/B25221_05/web.1013/b14428/cmp30cfg.htm#BCGDBFFA

[alfred jones]

Did you made a typo ? Is not Id annotation should be placed before a field property ? You have put before getter mehod.

[Jayesh A Lalwani]

It works in both places. I don't have a preference either way, but you should stick to one way

[alfred jones]

Thanks.
I will have a database autoincrement id. Do i need to keep an id field in entity class?

[Tim McGuire]

alfred jones wrote:Thanks.
I will have a database autoincrement id. Do i need to keep an id field in entity class?

Yes, if you read the documentation I linked to, you will see that there are extra annotations for letting EJB know that the database will generate autoincrement id.

[alfred jones]

Tim McGuire wrote:

alfred jones wrote:Thanks.
I will have a database autoincrement id. Do i need to keep an id field in entity class?

Yes, if you read the documentation I linked to, you will see that there are extra annotations for letting EJB know that the database will generate autoincrement id.

Ok. I have visited the link . Its very much confusing.

I see it has @GeneratedIdTable and @TableGenerator annotation . I am not yet sure which particular annotation will fit my requirement for database autoincrement id .

Are both annotations doing same thing ?

[Tim McGuire]

I just realized the documentation I linked to is for OC4J, which has a subset of the annotations. In other words, forget that link

If you are like me and have an object in your database called a "sequence", then you want something like this:

 @Id
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "hch_sequence")
    @SequenceGenerator(name = "hch_sequence", sequenceName = "hch_sequence")
@Column(name = "hch_id", unique = true, nullable = false)

[alfred jones]

Tim McGuire wrote:I just realized the documentation I linked to is for OC4J, which has a subset of the annotations. In other words, forget that link

If you are like me and have an object in your database called a "sequence", then you want something like this:

 @Id
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "hch_sequence")
    @SequenceGenerator(name = "hch_sequence", sequenceName = "hch_sequence")
@Column(name = "hch_id", unique = true, nullable = false)

You have ...

generator = "hch_sequence"
name = "hch_sequence"
sequenceName = "hch_sequence"

Do I need keep all similar names ? if not which names could be different ?


However, I dont have "sequence". MySQL does not support sequence. I have put id field as auto increment in MySQL database. Is it not possible using JPA in MySQL ?

[alfred jones]

alfred jones wrote:

Tim McGuire wrote:I just realized the documentation I linked to is for OC4J, which has a subset of the annotations. In other words, forget that link

If you are like me and have an object in your database called a "sequence", then you want something like this:

 @Id
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "hch_sequence")
    @SequenceGenerator(name = "hch_sequence", sequenceName = "hch_sequence")
@Column(name = "hch_id", unique = true, nullable = false)

You have ...

generator = "hch_sequence"
name = "hch_sequence"
sequenceName = "hch_sequence"

Do I need keep all similar names ? if not which names could be different ?


However, I dont have "sequence". MySQL does not support sequence. I have put id field as auto increment in MySQL database. Is it not possible using JPA in MySQL ?

comments please