RE: Is "Mapping Classes on Multiple Joined Tables" supported?
Hi Vadim, Stick to the Repository file I posted earlier! If you don't use the abstract modifier for the super class it works. Regards, Nils - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Howto handle inheritance with an abstract classes
Nils Liebelt wrote: Hi, I am struggling with a simple extend of an abstract class, trying to use multiple joined tables. I get following MetadataException: Can't create new base class object for 'za.co.ibn.datasolutions.entities.Contact' A soon as I remove the abstract modifier everything works. Here's my Repository: class="za.co.ibn.datasolutions.entities.Contact" table="Contact" name="contactID" column="contactID" jdbc-type="INTEGER" primarykey="true" autoincrement="true" > name="address" column="address" jdbc-type="VARCHAR" length="254" > class="za.co.ibn.datasolutions.entities.Individual" table="Individual" It really don't know what else to try. Did everything according to the advanced technique tutorial. The problem seems to be that for storing/materializing an instance of Individual, a concrete instance of the type referenced by the super-reference is needed. But since this class is abstract, no such object can be built. While this scenario may sound feasible in Java terms (because the fields of Contact are duplicated in Individual), when mapped to a reference OJB's behaviour actually makes sense because the mapping is a 'normal' reference. Only there is no concrete field to implement the reference on the Java side, but rather an anonymous field is used by OJB to store the end of the reference (an instance of Contact) and the values of this object are then used for the Individual instance. So, I'd say there is currently no way around making Contact a concrete class. Tom - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Is "Mapping Classes on Multiple Joined Tables" supported?
Vadim Gritsenko wrote:
Hey All,
[Using OJB_1_0_RELEASE branch from CVS]
As other users here, I'm also struggling with mapping class hierarchy
on multiple joined tables, and can't figure out what's wrong and
whether it is working at all or not.
Consider this slightly modified (added relation to the class C)
example from the OJB manual page [1]:
/**
* @ojb.class
* @ojb.extent-class class-ref="B"
*/
public class A {
/** @ojb.field primarykey="true" autoincrement="ojb" */
Integer id;
/** @ojb.field */
Integer cId;
/** @ojb.reference foreignkey="cId" */
C c;
}
/**
* @ojb.class include-inherited="false"
* @ojb.reference class-ref="A" foreignkey="aId"
* auto-retrieve="true" auto-update="object" auto-delete="object"
*/
public class B extends A
{
/** @ojb.field primarykey="true" autoincrement="ojb" */
Integer id;
/** @ojb.field */
Integer aId;
/** @ojb.field length="254" */
String value;
}
/**
* @ojb.class
*/
public class C {
/** @ojb.field primarykey="true" autoincrement="ojb" */
Integer id;
/** @ojb.field length="30" */
String name;
}
Ok, once we have that, problems start. First problem is that xdoclet
does not like include-inherited="false", and when
include-inherited="true", it generates all inherited attributes into
repository.xml - but we don't want them there! After some patching of
xdoclet [2], we can get desired result:
Mhmm, don't know what version of the XDoclet module you're using but
with the classes that you posted it works for me out-of-the-box (current
version that comes with 1.0.1) and generates exactly this repository file:
Assuming that all of the above is correct, I'm getting following
problems on run time:
1. First problem happens when trying to create instance of B (and
assuming that there is a record for C) with the code:
B b = new B();
b.cId = 1;
b.value = "dummy";
broker.store(b);
This fails with KeyConstraintViolatedException. Seems it is happening
because B's ClassDescriptor.getSuperClass() returns null and
PersistentBrokerImpl.storeToDb does not store base class. So what's
wrong, and can somebody clarify what's the difference between
getBaseClass and getSuperClass methods? At least getBaseClass() is
populated correctly.
I'm no expert on the mapping to multiple tables, but this is actually a
SQL exception coming from the database (I suspect Hsqldb in your case)
saying that the foreignkey constraint is violated while inserting a row
into the A table. This can only mean that the referenced C object is not
present.
You can turn off the generation of the foreign key constraints via the
generate-foreignkey attribute of the torqueschema Ant task
2. Second problem happens when trying to load existing instance from
the DB. Fails with OJBRuntimeException "Incorrect or not found field
reference name 'cId' in descriptor for class-descriptor 'B'.
Seems like ObjectReferenceDescriptor does not take into account B's
super class at all.
Strange, this code works just fine for me:
B bObj = new B();
C cObj = new C();
cObj.name = "The C instance";
bObj.value = "The B instance";
bObj.c = cObj;
PersistenceBroker broker =
PersistenceBrokerFactory.defaultPersistenceBroker();
broker.beginTransaction();
broker.store(bObj);
broker.commitTransaction();
broker.close();
bObj = null;
cObj = null;
Criteria criteria = new Criteria();
criteria.addEqualTo("value", "The B instance");
QueryByCriteria query = new QueryByCriteria(B.class, criteria);
broker = PersistenceBrokerFactory.defaultPersistenceBroker();
broker.beginTransaction();
bObj = (B)broker.getObjectByQuery(query);
broker.abortTransaction();
System.out.println("Loaded B: '"+bObj.value+"' referencing C:
'"+bObj.c.name+"'");
It prints (as expected):
Loaded B: 'The B instance' referencing C: 'The C instance'
Tom
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Re: Is "Mapping Classes on Multiple Joined Tables" supported?
Thomas Dudziak wrote:
Vadim Gritsenko wrote:
Hey All,
[Using OJB_1_0_RELEASE branch from CVS]
As other users here, I'm also struggling with mapping class hierarchy
on multiple joined tables, and can't figure out what's wrong and
whether it is working at all or not.
Consider this slightly modified (added relation to the class C)
example from the OJB manual page [1]:
/**
* @ojb.class
* @ojb.extent-class class-ref="B"
*/
public class A {
/** @ojb.field primarykey="true" autoincrement="ojb" */
Integer id;
/** @ojb.field */
Integer cId;
/** @ojb.reference foreignkey="cId" */
C c;
}
/**
* @ojb.class include-inherited="false"
* @ojb.reference class-ref="A" foreignkey="aId"
* auto-retrieve="true" auto-update="object" auto-delete="object"
*/
public class B extends A
{
/** @ojb.field primarykey="true" autoincrement="ojb" */
Integer id;
/** @ojb.field */
Integer aId;
/** @ojb.field length="254" */
String value;
}
/**
* @ojb.class
*/
public class C {
/** @ojb.field primarykey="true" autoincrement="ojb" */
Integer id;
/** @ojb.field length="30" */
String name;
/** @ojb.collection element-class-ref="A" foreignkey="cId" */
Collection a;
}
Ok, once we have that, problems start. First problem is that xdoclet
does not like include-inherited="false", and when
include-inherited="true", it generates all inherited attributes into
repository.xml - but we don't want them there! After some patching of
xdoclet [2], we can get desired result:
Mhmm, don't know what version of the XDoclet module you're using but
with the classes that you posted it works for me out-of-the-box (current
version that comes with 1.0.1)
I'm sorry, I forgot to add Collection of A's in C (see above). With this
collection, xdoclet fails - for both 1.0.1 release and 1.0.x branch (I'm working
off the branch as mentioned above).
and generates exactly this repository file:
Assuming that all of the above is correct, I'm getting following
problems on run time:
1. First problem happens when trying to create instance of B (and
assuming that there is a record for C) with the code:
B b = new B();
b.cId = 1;
b.value = "dummy";
broker.store(b);
This fails with KeyConstraintViolatedException. Seems it is happening
because B's ClassDescriptor.getSuperClass() returns null and
PersistentBrokerImpl.storeToDb does not store base class. So what's
wrong, and can somebody clarify what's the difference between
getBaseClass and getSuperClass methods? At least getBaseClass() is
populated correctly.
I'm no expert on the mapping to multiple tables, but this is actually a
SQL exception coming from the database (I suspect Hsqldb in your case)
saying that the foreignkey constraint is violated while inserting a row
into the A table. This can only mean that the referenced C object is not
present.
Yes, it is not: first, you have to create record in table C, before trying
inserting record into table A. More on this below...
You can turn off the generation of the foreign key constraints via the
generate-foreignkey attribute of the torqueschema Ant task
But it's not desirable - fk constraints are a good thing to have.
2. Second problem happens when trying to load existing instance from
the DB. Fails with OJBRuntimeException "Incorrect or not found field
reference name 'cId' in descriptor for class-descriptor 'B'.
Seems like ObjectReferenceDescriptor does not take into account B's
super class at all.
Strange, this code works just fine for me:
B bObj = new B();
C cObj = new C();
cObj.name = "The C instance";
bObj.value = "The B instance";
bObj.c = cObj;
PersistenceBroker broker =
PersistenceBrokerFactory.defaultPersistenceBroker();
broker.beginTransaction();
broker.store(bObj);
broker.commitTransaction();
broker.close();
bObj = null;
cObj = null;
Criteria criteria = new Criteria();
criteria.addEqualTo("value", "The B instance");
QueryByCriteria query = new QueryByCriteria(B.class, criteria);
broker = PersistenceBrokerFactory.defaultPersistenceBroker();
broker.beginTransaction();
bObj = (B)broker.getObjectByQuery(query);
broker.abortTransaction();
System.out.println("Loaded B: '"+bObj.value+"' referencing C:
'"+bObj.c.name+"'");
Well, it's getting more strange still... I ran your code (without modifying C
class) and got (starting with first insert):
[org.apache.ojb.broker.accesslayer.sql.SqlGeneratorDefaultImpl] DEBUG:
SQL:INSERT INTO A (id,cId) VALUES (?,?)
[org.apache.ojb.broker.accesslayer.JdbcAccessImpl] DEBUG: executeInsert:
[EMAIL PROTECTED]
Exception in thread "main" org.apache.ojb.broker.KeyConstraintViolatedException:
SQL failure while insert object data fo
r class A, PK of the given object is [ id=42], object was [EMAIL PROTECTED]
Re: Is "Mapping Classes on Multiple Joined Tables" supported?
Nils Liebelt wrote: Hi Vadim, Stick to the Repository file I posted earlier! If you don't use the abstract modifier for the super class it works. I don't have abstract classes anywhere - my case is a bit different. It's about mapping classes A and B, where B extends A, to two tables, and class C has collection of A. Vadim - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: Isolation level for Persistence broker queries
Is there a particular reason I don't get my questions answered? Just to know it will save me some time in the future. Thanks. -Original Message- From: Vesely, Max [IT] Sent: Wednesday, December 29, 2004 5:48 PM To: ojb-user@db.apache.org Subject:Isolation level for Persistence broker queries Hello, Is there any way to specify isolation level for OJB query executed using Persistence Broker API? I can see that there's isolation-level attribute available for class-descriptor but documentation says it's only used in ODMG implementation. Any help would be greatly appreciated. Max. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Isolation level for Persistence broker queries
Vesely, Max [IT] wrote: Is there a particular reason I don't get my questions answered? Just to know it will save me some time in the future. Well, I would say it is because currently there are holidays, so you can only reasonably expect answers next week the earliest, I'd say. And the people that every once in a while check their mail (like myself) are likely not able to answer your question. I for one don't know much about the isolation level stuff so I can't help you there. Tom - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: Isolation level for Persistence broker queries
Thanks. I'll wait for the next week then. Max. -Original Message- From: Thomas Dudziak [mailto:[EMAIL PROTECTED] Sent: Thursday, December 30, 2004 7:04 PM To: OJB Users List Subject:Re: Isolation level for Persistence broker queries Vesely, Max [IT] wrote: >Is there a particular reason I don't get my questions answered? Just to know >it will save me some time in the future. > > Well, I would say it is because currently there are holidays, so you can only reasonably expect answers next week the earliest, I'd say. And the people that every once in a while check their mail (like myself) are likely not able to answer your question. I for one don't know much about the isolation level stuff so I can't help you there. Tom - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
