Hello everybody
We've encountered a problem with an Entiy Bean. If we make an instance of the
folowing bean persistent while the collection are empty they are added to the
database correctly. The retrieval of the data works also.
But: As soon as more than one collection contains more than one element we
following problem occurs: The bean-data is fetched by a LEFT OUTER JOIN query
(Found out with Ethereal). This causes the collections to contain as much
elements as rows are returned by the DBMS.
Example
Collection1: 3 entries
Collection2: 4 entries
JOIN causes the collections to contain 12 entries (cartesian product)
-> This is an undesired effect.
Relevant bean code
@Entity(access=AccessType.PROPERTY)
| @Table(name="BibliographicData")
| public class BibliographicData implements Serializable {
|
| private int id;
|
| private List<String> abstracts = new LinkedList<String>();
| private List<String> inventors = new LinkedList<String>();
| private List<String> applicants = new LinkedList<String>();
|
|
| @OneToMany(fetch=FetchType.EAGER)
| public List<String> getAbstracts() {
| return abstracts;
| }
|
| @OneToMany(fetch=FetchType.EAGER)
| public List<String> getApplicants() {
| return applicants;
| }
|
| @OneToMany(fetch=FetchType.EAGER)
| public List<String> getInventors() {
| return inventors;
| }
|
| ....
| }
|
|
|
Workaround
Removal of @OneToMany causes JBoss to store the collections in serialized form.
The problem disappears.
Question
Is there a clever way to store the collections in separate tables without
separating them into individual entity beans?
Thanks for your help!
Regrads, Mike
JBoss Configuration
JBoss Version: 4.0.3 SP1
Sun JRE5 Build 1.5.0_06-b05
Debian Linux (Sarge)
MySQL 5.0.22
Changes in mysql-ds.xml
| <datasources>
| <local-tx-datasource>
| <jndi-name>MySqlDS</jndi-name>
| <connection-url>jdbc:mysql://localhost:3306/jbossdb</connection-url>
| <driver-class>com.mysql.jdbc.Driver</driver-class>
| <user-name>jboss</user-name>
| <password>insertpasswdhere</password>
|
<exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter</exception-sorter-class-name>
| <!-- sql to call when connection is created
| <new-connection-sql>some arbitrary sql</new-connection-sql>
| -->
| <!-- sql to call on an existing pooled connection when it is obtained
from pool
| <check-valid-connection-sql>some arbitrary
sql</check-valid-connection-sql>
| -->
|
| <!-- corresponding type-mapping in the standardjbosscmp-jdbc.xml
(optional) -->
| <metadata>
| <type-mapping>mySQL</type-mapping>
| </metadata>
| </local-tx-datasource>
| </datasources>
|
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