Solved

Creating Entity bean for a 'table' without PrimaryKey

Posted on 2004-09-17
6
359 Views
Last Modified: 2013-11-24
Hi,

I have a relation table without primarykey. My table name is "favorite" and it has:
worker_id   int   (FK to "worker" table)
task_id   int   (FK to "tasks" table)
priority   int

If i want to create an Entity Bean, we usually create all the 'columns' with getter and setter along with the column type. For example, (just an example):
           
     /**
       * @author bj 17.09.2004
       * Name
       *
       * @ejb.interface-method view-type = "both"
       * @ejb.persistence column-name = "name"
       * @return
       */
      public abstract String getName();

      /**
       * @ejb.interface-method view-type = "both"
       * @param name
       */
      public abstract void setName(String name);


The method ejbCreate() should have the return type of PrimaryKey. My every other table has a PK field and i do like:
     public Integer ejbCreate() throws CreateException {
            return null;
    }

Since my "Favorite" table doesn't have a PK field, how can i create en Entity bean for that table? How to solve the problem of ejbCreate() return type?
0
Comment
Question by:ldbkutty
  • 4
  • 2
6 Comments
 
LVL 35

Expert Comment

by:TimYates
ID: 12083032
It does have a primary key.  The primary key is a composite of:

  worker_id and task_id

isn't it?

Have a look at this:  http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/CMP8.html (for CMP) and this http://java.sun.com/j2ee/1.4/docs/tutorial/doc/BMP4.html (for BMP)

0
 
LVL 32

Author Comment

by:ldbkutty
ID: 12083168
I understand that PK is combination of worker_id and task_id, but i cannot/shouldn't  create the FK fields(getter, setter) in my Entity Bean. Instead I have to make the relation for those FK's.

For example, in my "Tasks" table, i have 'taskworker_id' FK column to "TaskWorker" table. In my Entity bean, i have:

     /**
       * @author bj 16.09.2004
       *
       * Task TaskWorker Relation
       *
       * @ejb.interface-method
       *       view-type = "local"
       *
       * @ejb.relation
       *       name = "taskworker_task"
       *          role-name = "task from taskworker"
       *
       * @jboss.relation
       *       fk-column = "'taskworker_id"
       *       related-pk-field = "id"
       *       fk-constraint = "true"
       */
      public abstract TaskWorkerLocal getTaskWorker();

      /**
       * @ejb.interface-method view-type = "local"
       * @param taskWorker
       */
      public abstract void setTaskWorker(TaskWorkerLocal taskWorker);
0
 
LVL 35

Accepted Solution

by:
TimYates earned 500 total points
ID: 12083273
> Instead I have to make the relation for those FK's.

But you need to be able to access the "priority" field, so you will need to create an Entity bean for that table...

public class FavouritePK implements Serializable
{
    Worker worker ;
    Task task ;

    public FavouritePK() {}
    public FavouritePK( Worker worker, Task task )
    {
        this.worker = worker ;
        this.task = task ;
    }

    public Worker getWorker()
    {
        return worker ;
    }
   
    public Worker getTask()
    {
        return task ;
    }

    public boolean equals( Object o )
    {
        if( o == null || !(o instanceof FavouritePK ) )
            return false ;
        FavouritePK other = (FavouritePK)o ;
        return this.worker.equals( other.worker ) && this.task.equals( other.task ) ;
    }
 
    public int hashCode()
    {
        return worker.hashCode() ^ task.hashCode() ;
    }
}

Then, in your Entity bean:

public abstract class FavouriteBean implements javax.ejb.EntityBean
{
    Worker worker ;
    Task task ;
    int priority ;

    public FavouritePK ejbCreate( Worker w, Task t )
    {
        setWorker( worker ) ;
        setTask( task ) ;
        setPriority( priority ) ;
        return null ;
    }

    ...rest of your code...
}
0
Master Your Team's Linux and Cloud Stack

Come see why top tech companies like Mailchimp and Media Temple use Linux Academy to build their employee training programs.

 
LVL 35

Expert Comment

by:TimYates
ID: 12083274
>     public FavouritePK ejbCreate( Worker w, Task t )

should be

    public FavouritePK ejbCreate( Worker w, Task t, int priority )
0
 
LVL 32

Author Comment

by:ldbkutty
ID: 12114278
sorry for late...but that worked great.

Thanks.
0
 
LVL 35

Expert Comment

by:TimYates
ID: 12114386
:-)  Cool :-)

Good luck with it :-)

Tim
0

Featured Post

How Do You Stack Up Against Your Peers?

With today’s modern enterprise so dependent on digital infrastructures, the impact of major incidents has increased dramatically. Grab the report now to gain insight into how your organization ranks against your peers and learn best-in-class strategies to resolve incidents.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

INTRODUCTION Working with files is a moderately common task in Java.  For most projects hard coding the file names, using parameters in configuration files, or using command-line arguments is sufficient.   However, when your application has vi…
International Data Corporation (IDC) prognosticates that before the current the year gets over disbursing on IT framework products to be sent in cloud environs will be $37.1B.
Viewers will learn about arithmetic and Boolean expressions in Java and the logical operators used to create Boolean expressions. We will cover the symbols used for arithmetic expressions and define each logical operator and how to use them in Boole…
This tutorial covers a step-by-step guide to install VisualVM launcher in eclipse.

820 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question