From noreply at atlassian.com Fri Mar 11 11:33:08 2011
Content-Type: multipart/mixed; boundary="===============1474489798802995589=="
MIME-Version: 1.0
From: Joachim Durchholz (JIRA) <noreply at atlassian.com>
To: hibernate-issues at lists.jboss.org
Subject: [hibernate-issues] [Hibernate-JIRA] Created: (HBX-1179) <one-to-one>
 should not generate Sets
Date: Fri, 11 Mar 2011 10:33:08 -0600
Message-ID: <2104628549.1666.1299861188160.JavaMail.j2ee-opensource-projects@vps07.contegix.com>

--===============1474489798802995589==
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable

<one-to-one> should not generate Sets
-------------------------------------

                 Key: HBX-1179
                 URL: http://opensource.atlassian.com/projects/hibernate/br=
owse/HBX-1179
             Project: Hibernate Tools
          Issue Type: Bug
          Components: reverse-engineer
         Environment: Hibernate Tools version as reported by Eclipse: 3.3.0=
.v20101016-0359-H111-Beta1
Feel free to identify the matching release numbers, I can't :-/
            Reporter: Joachim Durchholz


Hibernate tools does not always recognize one-to-one associations as such, =
even if specified as <one-to-one> in hibernate.reveng.xml.

1. It should generally not silently fall back to one-to-many or many-to-one=
 if it determines that one-to-one is not possible; it should report an erro=
r instead. (This allows programmers to correct the database and/or the hibe=
rnate.reveng.xml: if it's really a one-to-many, they can move the associati=
on to the other table and make it many-to-one; if it should be one-to-one, =
they can add the missing constraints, giving Hibernate better information a=
bout the database schema actually in place.)
2. In the following test case, it does not recognize the relationship as on=
e-to-one even though it is, erroneously generating a Set for the <inverse-o=
ne-to-one> direction instead of a backlink.

Workarounds:
A) Use <inverse-one-to-one exclude=3D"true"/> to prevent Set creation. Work=
s if you don't need the backlink.
B) Have a backlink field in the target table. Create two one-to-one associa=
tions, one for each direction, and use <inverse-one-to-one exclude=3D"true"=
/>.
C) Do not reverse engineer the one-to-one association at all and use Criter=
ia, HQL, or SQL to navigate the link.
D) Subclass DefaultReverseEngineeringStrategy and override isOneToOne() for=
 that particular association.

Test case:

Table creation (Oracle 10g)

CREATE TABLE "HF_DI_BVKRIT" (
  "BKID" NUMBER(27,0) NOT NULL ENABLE,
  "VERSION" NUMBER(18,0) DEFAULT 0 NOT NULL ENABLE,
  "BKNAME" VARCHAR2(40) NOT NULL ENABLE
) ;
ALTER TABLE "HF_DI_BVKRIT" ADD CONSTRAINT "HF_DI_BVKRIT_PK"
  PRIMARY KEY ("BKID") ENABLE;

CREATE TABLE "HF_DI_BVKOPF" (
  "BVID" NUMBER(10,0) NOT NULL ENABLE,
  "VERSION" NUMBER(18,0) DEFAULT 0 NOT NULL ENABLE,
  "BVBKID" NUMBER(27,0) NOT NULL ENABLE,
  "BVGPRS" NUMBER(8,2)
) ;
ALTER TABLE "HF_DI_BVKOPF" ADD CONSTRAINT "HF_DI_BVKOPF_PK"
  PRIMARY KEY ("BVID") ENABLE;
ALTER TABLE "HF_DI_BVKOPF" ADD CONSTRAINT "HF_DI_BVKOPF_UK"
  UNIQUE ("BVBKID") ENABLE;
ALTER TABLE "HF_DI_BVKOPF" ADD CONSTRAINT "HF_DI_BVKOPF_FK_BVKRIT"
  FOREIGN KEY ("BVBKID") REFERENCES "HF_DI_BVKRIT" ("BKID") ENABLE;

Relevant hibernate.reveng.xml section:

  <table name=3D"HF_DI_BVKOPF">
    <column name=3D"VERSION" type=3D"long"></column>
    <foreign-key constraint-name=3D"HF_DI_BVKOPF_FK_BVKRIT">
      <one-to-one />
      <inverse-one-to-one />
    </foreign-key>
  </table>

Generated Java classes:

public class HfDiBvkrit implements java.io.Serializable {
  private BigInteger bkid;
  private long version;
  private String bkname;
  private Set <HfDiBvkopf> hfDiBvkopfs =3D new HashSet <HfDiBvkopf> (0);
  // The above line should have been generated as:
  // private HfDiBvkopf hfDiBvkopf;
  ...
}
public class HfDiBvkopf implements java.io.Serializable {
  private BigInteger bvid;
  private long version;
  private HfDiBvkrit hfDiBvkrit;
  private BigDecimal bvgprs;
  ...
}

Reasoning why this should be a one-to-one association (hopefully I didn't m=
ake too many errors reversing the roles of left and right table):

There is a unique key on BVKOPF.BVBKID.
I.e. a BVKRIT record can find at most one BVKOPF with a BVBKID that matches=
 its BVKRIT.BKID.
The BVKOPF-BVKRIT association hence must be one-to-*. (1)

There is a foreign key from BVKOPF.BVBKID to BVKRIT.BKID.
BKID is a unique key in BVKRIT (it also happens to be the primary key, but =
that's irrelevant here).
I.e. a BVKOPF record can find at most one BVKRIT with a BKID that matches i=
ts BVKOPF.BVBKID.
The BVKOPF-BVKRIT association hence must be *-to-one. (2)

Combining (1) and (2) gives "must be one-to-one", q.e.d.

See also https://forum.hibernate.org/viewtopic.php?f=3D6&t=3D1009989&start=
=3D0

-- =

This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators: htt=
p://opensource.atlassian.com/projects/hibernate/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira

       =20

--===============1474489798802995589==--