12 Replies Latest reply on Jan 19, 2003 12:48 PM by Scott Van Kirk

    simple cmr problem, but it is killing me

    Craig Hamilton Newbie

      I am trying to implement a 1:N cmr, but I keep getting the following error when I try and deploy

      jboss.deployment.DeploymentException: Both roles of a relation-table mapped relationship must have key fields:

      here is the relationships section from ejb-jar.xml

      <ejb-relation >
      <ejb-relation-name>activities-have-details</ejb-relation-name>

      <ejb-relationship-role >
      <ejb-relationship-role-name>role-name</ejb-relationship-role-name>
      One
      <relationship-role-source >
      <ejb-name>ActivityBean</ejb-name>
      </relationship-role-source>
      <cmr-field >
      <cmr-field-name>details</cmr-field-name>
      <cmr-field-type>java.util.Collection</cmr-field-type>
      </cmr-field>
      </ejb-relationship-role>

      <ejb-relationship-role >
      <ejb-relationship-role-name>details-belong-to-activity</ejb-relationship-role-name>
      Many
      <relationship-role-source >
      <ejb-name>ActivityDetailBean</ejb-name>
      </relationship-role-source>
      </ejb-relationship-role>

      </ejb-relation>



      and here is the corresponding section in the jbosscmp-jdbc file:

      <ejb-relation>
      <ejb-relation-name>activities-have-details</ejb-relation-name>

      <foreign-key-mapping/>

      <ejb-relationship-role>
      <ejb-relationship-role-name>role-name</ejb-relationship-role-name>
      <key-fields>
      <key-field>
      <field-name>activityid</field-name>
      <column-name>activityid</column-name>
      </key-field>
      <key-field>
      <field-name>year</field-name>
      <column-name>year</column-name>
      </key-field>
      </key-fields>
      </ejb-relationship-role>
      <ejb-relationship-role>
      <ejb-relationship-role-name>details-belong-to-activity</ejb-relationship-role-name>
      <key-fields/>
      </ejb-relationship-role>
      </ejb-relation>


      I have read the CMP documentation, but still can't seem to get it right.

      Does anyone have a simple two bean example of 1-many which uses xdoclet, specifically for jboss?

      thanks,

      craig

        • 1. Re: simple cmr problem, but it is killing me
          Loren Rosen Newbie

          In your jbosscmp-jdbc.xml file you have in part

          <ejb-relationship-role>
          <ejb-relationship-role-name>details-belong-to-activity</ejb-relationship-role-name>
          <key-fields/>
          </ejb-relationship-role>
          </ejb-relation>


          So this end of the relationship is not defining any
          key fields. You need to define this the same way as you
          did in the other direction, e.g., using the @jboss:relation tag.

          • 2. Re: simple cmr problem, but it is killing me
            Craig Hamilton Newbie

            don't i only need this end of the relationship defined if it is bi-directional?

            • 3. Re: simple cmr problem, but it is killing me
              Loren Rosen Newbie

              Oh, right, you're doing one-to-many. Don't
              know why you're getting an error message
              about relation-table mapping.

              Looking more closely I see a couple of
              possible problems with your jbosscmp-jdbc
              file. Or perhaps I've got something turned
              around -- it's easy to do with this stuff.

              To define the relationship ultimately the
              detail table will need columns corresponding
              to each column of the master's primary key.
              This is the reverse of the way you might do
              an object model -- one thing to possibly
              get turned around about. (Also, in principle
              we could use any unique key of the master, but
              let's leave that aside for the moment.)

              So for each column in the master's primary
              key we need to specify the name of the
              corresponding column in the detail table.
              Concretely this is done in the <key-fields>
              part of the fle. I would
              guess here that activityId is the primary
              key of the master, and from that standpoint
              you have specified this superfluous year column.
              I would further guess that (activityId, year)
              is the primary key of the detail table, and from
              that standpoint you've gotten turned around
              about whether to specify the primary key of
              the master or of the detail table.

              The latter guess points to the second likely
              problem. It looks like you're using the common
              idiom in which the detail table has the master's
              primary key as part of its composite primary
              key. Or to put that another way the foreign
              key field is part of the primary key. Problem
              is jBoss doesn't support this. But since this
              problem comes up a lot there is a (very new)
              patch for it.

              Let me know if I've got this right -- I'd rather
              be publicly chagrined than be totally off-track
              but not know it.

              • 4. Re: simple cmr problem, but it is killing me
                t g Newbie

                I'm having this problem too. The "One" table has one column as the primary key. The "Many" table has a foreign key of the "One" table and another column representing a composite key. JBoss does not seem to handle this relational design well. For example, with cascade deletes it sets to null the foreign key field in the "Many" table. Because I would like this column not null, I have problems.

                • 5. Re: simple cmr problem, but it is killing me
                  Brian Benton Newbie

                  > I'm having this problem too. The "One" table has one
                  > column as the primary key. The "Many" table has a
                  > foreign key of the "One" table and another column
                  > representing a composite key.

                  If I understand you correctly, you are trying to implement a true identifying relationship in the physical database. I tend to use another approach that yields the same results, but does not require the FK in the child table to migrate to the PK. See below.

                  > JBoss does not seem to
                  > handle this relational design well. For example,
                  > with cascade deletes it sets to null the foreign key
                  > field in the "Many" table.

                  Yes, JBoss CMP has a hangup in that it does not allow FKs to be 'not null'.

                  When implementing identifying relationships in the physical database, I never migrate the FK to become part of the PK. I prefer to stick to non-composite surrogate PKs as they perform better (I do use composite PKs in certain situations when I need to implement inheritance). I then simply constrain the FK to be 'not null'. Once JBoss CMP is rectified to handle 'not null' FKs, I would recommend this approach in implementing identifying relationships.

                  Regards,
                  Brian

                  > Because I would like this
                  > column not null, I have problems.

                  • 6. Re: simple cmr problem, but it is killing me
                    t g Newbie

                    Yea I agree with you. But I'm not the DBA. I have to adapt my ejb's to an existing database structure.
                    Overall JBoss rocks, and combined with the rapid open source app tool Xdoclet I'm extremely impressed.

                    • 7. Re: simple cmr problem, but it is killing me
                      t g Newbie

                      The database folks have told me that the "Many" table that has a composite key (which includes a column that is a foreign key) does not exist without the "One" parent table. Therefore philisophically a child does not exist on it's own and should be aware of it's parent. Hence the composite key in the "Many" table has two columns, one of which is a foreign key. Because the foreign key is part of the composite key, I can't use JBoss to manage relationships because JBoss set's foreign keys to null for various transactions. Any JBoss "core" folks have any comments and is there anything in the works to remedy this problem.

                      • 8. Re: simple cmr problem, but it is killing me
                        Alex Shneyderman Newbie

                        I am not sure if it is the same problem but I had the same message and the reason for it was that my
                        ejb-jar file did not have a <primkey-field> for my primary key field in my master entity.

                        So I guess if you put <primkey-field>activityId</primkey-field> in the Activity bean's descriptor, it might help your problem.

                        • 9. Re: simple cmr problem, but it is killing me
                          Craig Hamilton Newbie

                          The activityid and year column form the primary key in the master table, and these fields exist in the detail table which make up the foreign key.

                          My detail table doesn't have a primary key.

                          In reading other posts in the forum it seems composite pk's are a problem. Unfortunately I am trying to model the ejb's on top of an existing database, so changing the structure of the database is not painless.

                          Does this patch you mentioned handle composite pk's? I just downloaded 3.2b3, does this contain the patch mentioned?

                          thanks for the help,

                          craig

                          • 10. Re: simple cmr problem, but it is killing me
                            Loren Rosen Newbie

                            The patch (actually, the change note) is described here
                            http://sourceforge.net/mailarchive/forum.php?thread_id=1456333&forum_id=7101
                            or with slightly less detail
                            http://sourceforge.net/tracker/index.php?func=detail&aid=658296&group_id=22866&atid=381174

                            I can't tell from the note whether it supports composite keys or not. The update is for 3.2, but I don't know if
                            it's been incorporated yet or not.

                            • 11. Re: simple cmr problem, but it is killing me
                              Ignacio de Cordoba Novice

                              Could anybody please confirm if current JBoss (v3.0.4) supports this?
                              I have the problem described in previous message in this forum. In my Newsletter <-> NewsletterSubscribers situation, does this mean that, in the subscriber EJB, making the CMP field "newsletter" and the CMR field also "newsletter" have that exact name (now the CMP is newsletterid and the CMR newsletter) will make it work?

                              Thanks,
                              Ignacio

                              • 12. Re: simple cmr problem, but it is killing me
                                Scott Van Kirk Newbie

                                This does not work in 3.0.4 for the creation of tables. When you have an identical cmp and cmr field, JBoss generates a sql create which tries to include two columns of the same name. I do not know if, once the columns are created it will do the right thing with other functions.