Serialization with @Transient fields
Hello everybody,
I have created an entity having attributes which should be
persisted and attriutes which should not be persisted marked with the
@Transient annotation. For example it is something like this:
@Entity
public class MyEntity implements Serializable
{
@Column
protected int myInteger;
@Transient
protected List myList;
// And so on
}
I need the transient field for holding some content during the
application which
needs not to be persisted.
Now I want to serialize MyEntity, but there is the problem: All fields
marked
with @Transient are not serialized. I know there is the "transient"
modifier which
excludes attributes from serialization, but has @Transient the same effect?
How can I make the application serializing @Transient fields without
having to persist them?
Has anyone an idea?
Greetings!
Naomi
Re: Inheritance: Subclasses are not recognised
Hello everybody,
after spending half of my weekend, I got it to work. I do not know exactly WHY
it works that way, but I think this is marginal ;)
If someone can explain it to me, feel free to do so, I would be glad.
It seems that the cause was a combination of bad Spring configuration and some
anomalies in my project. So lets have a look on how I solved the problem:
First, I wanted to try to persist one of the subclasses, because I wanted to
see what discriminator value would be written to the database.
Because I only need to read that subclass from other objects and do not need to
call them directly from database, I created a new Spring DAO for this persist
task. I found out, that persisting did not work either and thus realised that I
did not include a transaction manager (it was configured, but not linked - too
bad :\ ).
After reconfiguring the Spring framework I was able to persist the entity
without any problems. After that, I ran my application again and - it suddenly
recognised the entity persisted before (but still not the other subclasses).
After some try-and-error, I found out:
To make Spring / OpenJPA recognise the discriminator values, the subclasses
have to be
a) directly related to any entity, that can be called with a Spring DAO
or
b) directly called with a Spring DAO
If only the superclass is related / called, the discriminator value of the
subclasses will not be recognised.
Maybe some OpenJPA / Spring experts will laugh at me, but please explain me,
why it works that way ^^"
Original-Nachricht
> Datum: Fri, 15 May 2009 16:47:31 +0200
> Von: "Jasmin Riemer"
> An: users@openjpa.apache.org
> Betreff: Re: Inheritance: Subclasses are not recognised
> Hi Mike,
>
> yes, I have.
> This was also my first thought about that problem ;)
> Maybe other configurations in persistence.xml that may cause problems?
>
>
>value="root"/>
>
>value="jdbc:mysql://localhost:3306/ghostbase"/>
>value="com.mysql.jdbc.Driver"/>
>value="mysql(TableType=myisam)"/>
>
>
>
> -Jasmin
>
> Original-Nachricht
> > Datum: Fri, 15 May 2009 09:25:54 -0500
> > Von: Michael Dick
> > An: users@openjpa.apache.org
> > Betreff: Re: Inheritance: Subclasses are not recognised
>
> > Hi Jasmin,
> >
> > Do you have all your entities listed in persistence.xml?
> >
> > -mike
> >
> > On Fri, May 15, 2009 at 7:08 AM, Jasmin Riemer
> > wrote:
> >
> > > Hello everybody,
> > >
> > > currently, I am working with OpenJPA in the Spring framework and try
> to
> > > implement the following:
> > >
> > > I inherit certain subclasses from a mainclass. All these classes
> should
> > be
> > > mapped to a single table, so I use InheritanceType.SINGLE_TABLE and
> add
> > a
> > > discriminator value to each subclass.
> > >
> > > Simplified, it looks like this:
> > >
> > > @Entity
> > > @Inheritance(strategy=InheritanceType.SINGLE_TABLE)
> > > @DiscriminatorColumn(name="doc_type",
> > > discriminatorType=DiscriminatorType.STRING)
> > > public abstract class Document {
> > >
> > > // ...
> > >
> > > }
> > >
> > > @Entity
> > > @DiscriminatorValue(value="Magazine")
> > > public class Magazine extends Document {
> > >
> > > // ...
> > >
> > > }
> > >
> > > @Entity
> > > @DiscriminatorValue(value="Book")
> > > public class Book extends Document {
> > >
> > > // ...
> > >
> > > }
> > >
> > > Unfortunately, I get the following error message when I try to load
> data
> > > from the database:
> > >
> > > Exception in thread "main"
> > > org.springframework.dao.InvalidDataAccessApiUsageE xception: Could not
> > map
> > > discriminator value "Book" to any known subclasses of the requested
> > class
> > > "project.entities.Document" (known discriminator values: [Document,
> > > Magazine]).; nested exception is nonfatal
> > user
> > > error> org.apache.openjpa.persistence.ArgumentException: Could not map
> > > discriminator value "Book" to any known subclasses of the requested
> > class
> > > "project.entities.Document" (known discriminator values: [Document,
> >
Re: Inheritance: Subclasses are not recognised
Hi Mike,
yes, I have.
This was also my first thought about that problem ;)
Maybe other configurations in persistence.xml that may cause problems?
-Jasmin
Original-Nachricht
> Datum: Fri, 15 May 2009 09:25:54 -0500
> Von: Michael Dick
> An: users@openjpa.apache.org
> Betreff: Re: Inheritance: Subclasses are not recognised
> Hi Jasmin,
>
> Do you have all your entities listed in persistence.xml?
>
> -mike
>
> On Fri, May 15, 2009 at 7:08 AM, Jasmin Riemer
> wrote:
>
> > Hello everybody,
> >
> > currently, I am working with OpenJPA in the Spring framework and try to
> > implement the following:
> >
> > I inherit certain subclasses from a mainclass. All these classes should
> be
> > mapped to a single table, so I use InheritanceType.SINGLE_TABLE and add
> a
> > discriminator value to each subclass.
> >
> > Simplified, it looks like this:
> >
> > @Entity
> > @Inheritance(strategy=InheritanceType.SINGLE_TABLE)
> > @DiscriminatorColumn(name="doc_type",
> > discriminatorType=DiscriminatorType.STRING)
> > public abstract class Document {
> >
> > // ...
> >
> > }
> >
> > @Entity
> > @DiscriminatorValue(value="Magazine")
> > public class Magazine extends Document {
> >
> > // ...
> >
> > }
> >
> > @Entity
> > @DiscriminatorValue(value="Book")
> > public class Book extends Document {
> >
> > // ...
> >
> > }
> >
> > Unfortunately, I get the following error message when I try to load data
> > from the database:
> >
> > Exception in thread "main"
> > org.springframework.dao.InvalidDataAccessApiUsageE xception: Could not
> map
> > discriminator value "Book" to any known subclasses of the requested
> class
> > "project.entities.Document" (known discriminator values: [Document,
> > Magazine]).; nested exception is user
> > error> org.apache.openjpa.persistence.ArgumentException: Could not map
> > discriminator value "Book" to any known subclasses of the requested
> class
> > "project.entities.Document" (known discriminator values: [Document,
> > Magazine]).
> >
> > It seems that there are only known the main class and the subclass
> > "Magazine", but there is a problem with "Book" (and some other classes
> > inherited from "Document").
> >
> > I do not have much experience with OpenJPA and Spring and thus I have no
> > clue how to solve this problem. Anybody out there who has an idea or
> maybe
> > had a similar problem?
> > Is there maybe something special I could have used accidentally for
> > "Magazine", but not for the other classes?
> > --
> > Neu: GMX FreeDSL Komplettanschluss mit DSL 6.000 Flatrate +
> > Telefonanschluss für nur 17,95 Euro/mtl.!*
> > http://dslspecial.gmx.de/freedsl-surfflat/?ac=OM.AD.PD003K11308T4569a
> >
--
Neu: GMX FreeDSL Komplettanschluss mit DSL 6.000 Flatrate + Telefonanschluss
für nur 17,95 Euro/mtl.!*
http://dslspecial.gmx.de/freedsl-surfflat/?ac=OM.AD.PD003K11308T4569a
Inheritance: Subclasses are not recognised
Hello everybody,
currently, I am working with OpenJPA in the Spring framework and try to
implement the following:
I inherit certain subclasses from a mainclass. All these classes should be
mapped to a single table, so I use InheritanceType.SINGLE_TABLE and add a
discriminator value to each subclass.
Simplified, it looks like this:
@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="doc_type",
discriminatorType=DiscriminatorType.STRING)
public abstract class Document {
// ...
}
@Entity
@DiscriminatorValue(value="Magazine")
public class Magazine extends Document {
// ...
}
@Entity
@DiscriminatorValue(value="Book")
public class Book extends Document {
// ...
}
Unfortunately, I get the following error message when I try to load data from
the database:
Exception in thread "main" org.springframework.dao.InvalidDataAccessApiUsageE
xception: Could not map discriminator value "Book" to any known subclasses of
the requested class "project.entities.Document" (known discriminator values:
[Document, Magazine]).; nested exception is org.apache.openjpa.persistence.ArgumentException: Could
not map discriminator value "Book" to any known subclasses of the requested
class "project.entities.Document" (known discriminator values: [Document,
Magazine]).
It seems that there are only known the main class and the subclass "Magazine",
but there is a problem with "Book" (and some other classes inherited from
"Document").
I do not have much experience with OpenJPA and Spring and thus I have no clue
how to solve this problem. Anybody out there who has an idea or maybe had a
similar problem?
Is there maybe something special I could have used accidentally for "Magazine",
but not for the other classes?
--
Neu: GMX FreeDSL Komplettanschluss mit DSL 6.000 Flatrate + Telefonanschluss
für nur 17,95 Euro/mtl.!*
http://dslspecial.gmx.de/freedsl-surfflat/?ac=OM.AD.PD003K11308T4569a
