maho77 wrote:
Hello,
I have connected a MySQL Database to Geronimo via MySQL XA Pool. Further I
have two entities:
Country and Region. In the country Entity I mapped the Region as follows:
@OneToMany(cascade = ALL, targetEntity = entities.orig.Region.class,
mappedBy = "country")
@OrderBy("name ASC")
public Collection<Region> getRegion() {
return region;
}
In Region I mapped Country:
@ManyToOne(targetEntity=entities.orig.Country.class, cascade = { MERGE,
REFRESH })
@JoinColumn(name="country_id", referencedColumnName = "id", table =
"region")
public Country getCountry() {
return country;
}
I have the following schema for region:
CREATE TABLE region (
id INT NOT NULL AUTO_INCREMENT,
country_id INT DEFAULT 0 NOT NULL,
name VARCHAR(255) DEFAULT '' NOT NULL,
info_id INT DEFAULT 0 NOT NULL,
default_region BIT DEFAULT 0 NOT NULL,
PRIMARY KEY (id)
) ENGINE=MyISAM; //I tried ENGINE=InnoDB too with the same results
alter table region add foreign key(country_id) references country (id)
CREATE TABLE country (
id INT(4) NOT NULL AUTO_INCREMENT,
countrycode CHAR(2) DEFAULT '' NOT NULL,
name VARCHAR(255) DEFAULT '' NOT NULL,
default_region_id INT(2) DEFAULT 0 NOT NULL,
UNIQUE KEY(countrycode),
PRIMARY KEY (id)
) ENGINE=MyISAM // and also InnoDB;
This is my persistence.xml:
<persistence-unit name="JPATest">
<jta-data-source>TEST_XA</jta-data-source>
<class>entities.orig.Country</class>
<class>entities.orig.Region</class>
<properties>
<property name="openjpa.jdbc.SynchronizeMappings"
value="false" />
<property name="openjpa.jdbc.DBDictionary"
value="mysql(SupportsSubselect=true)" />
<property name="openjpa.Log"
value="DefaultLevel=TRACE,SQL=TRACE" />
</properties>
</persistence-unit>
When I run this I get the following exception from OpenJPA:
<openjpa-1.0.0-r420667:568756 nonfatal general error>
org.apache.openjpa.persistence.PersistenceException: Not unique table/alias:
't0' {prepstmnt 10955888 SELECT t0.id, t0.changed, t0.created,
t0.default_region, t1.id, t1.changed, t1.created, t1.infotext,
t1.user_changed, t1.user_created, t0.name, t0.user_changed, t0.user_created
FROM bo_test.region t0 INNER JOIN bo_test.region t0 ON t0.id = t0.Region_id
LEFT OUTER JOIN bo_test.info t1 ON t0.info_id = t1.id WHERE t0.country_id =
? [params=(int) 43]} [code=1066, state=42000]
When I use a mapping table and change the mapping it works:
Country:
@OneToMany(cascade = REFRESH, targetEntity = entities.Region.class,
fetch =
EAGER)
@OrderBy("name ASC")
@JoinTable(name="country_region", joinColumns =
@JoinColumn(name="country_id", referencedColumnName = "id"),
inverseJoinColumns = @JoinColumn(name="region_id", referencedColumnName =
"id"))
public Collection<Region> getRegion() {
return region;
}
Region:
@ManyToOne(targetEntity=entities.Country.class)
@JoinColumn(name = "country_id", referencedColumnName = "id", table =
"country_region")
public Country getCountry() {
return country;
}
What it going wrong here? Can anybody help me?
Thanks,
Mark
Hey Mark,
That one caught me too.
The JPA spec says that you have to use a mapping table to do a
one-to-many relationship.
But, OpenJPA has a proprietary annotation that you can use if you know
that you will not be using any other persistence engines:
@ElementJoinColumn(name="<child table ref column>"
referencedColumnName="<parent table ref column>")
That should allow you to bypass the 'standard' JPA relationship mapping
and get your one-to-many working.
Jay
