reader/writer design question for custom datatype

[Sideswipe]

I have a situation where I have several different input formats that
ultimately need to construct a List<Map<String,Object>> and at some
point I will need to write out the same datatype as well. Classic
serialization.

The input source could be a proprietary formatted config file, XML, a
Database, and so on.

I have in my mind that somehow implementing the Serializable interface
on my own subclasses of List an Map (implementing the writeObject()
and readObject()) respectively is what I am looking for.

Problem is though, it wants me to write to a stream -- in the case of
files, this isn't a problem but in the case of a Database it seems a
stretch to refer to a DB connection as some kinda stream (although not
an impossible stretch). And, I can't control what stream is passed to
those methods

Perhaps the better way would be to implement my own In/Out stream for
the different sources, and if it's and object of form List<map>, then
write out approrpriately. Then again, the writeInt/etc doesn't make
sense in the case of a DB because it is keyed. Only writeObject/
ReadObject has real meaning and only if it's the form I need

So, in summary: I need to load data from multiple sources and
reconstitute an object, then at some point turn it around and write it
back out.

I am looking for some ideas on this -- I would like to use the built
in Java facilities to do it


Christian Bongiorno
http://christian.bongiorno.org

 

[Daniel Pitts]

I have a situation where I have several different input formats that
ultimately need to construct a List<Map<String,Object>> and at some
point I will need to write out the same datatype as well. Classic
serialization.

The input source could be a proprietary formatted config file, XML, a
Database, and so on.

I have in my mind that somehow implementing the Serializable interface
on my own subclasses of List an Map (implementing the writeObject()
and readObject()) respectively is what I am looking for.

Problem is though, it wants me to write to a stream -- in the case of
files, this isn't a problem but in the case of a Database it seems a
stretch to refer to a DB connection as some kinda stream (although not
an impossible stretch). And, I can't control what stream is passed to
those methods

Perhaps the better way would be to implement my own In/Out stream for
the different sources, and if it's and object of form List<map>, then
write out approrpriately. Then again, the writeInt/etc doesn't make
sense in the case of a DB because it is keyed. Only writeObject/
ReadObject has real meaning and only if it's the form I need

So, in summary: I need to load data from multiple sources and
reconstitute an object, then at some point turn it around and write it
back out.

I am looking for some ideas on this -- I would like to use the built
in Java facilities to do it

Christian Bongiornohttp://christian.bongiorno.org

Serialization and databases don't mix well. Look into a ORM solution
if you want to persist your java objects into a database.

I suggest Hibernate or Ibatis.

There are also utilities that will help you save object graph to an
XML file, but I don't have as much experience with those.

 

[Lew]

Serialization and databases don't mix well. Look into a ORM solution
if you want to persist your java objects into a database.

I suggest Hibernate or Ibatis.

There are also utilities that will help you save object graph to an
XML file, but I don't have as much experience with those.

The Java Persistence API would likely be useful, too.

 

[Roedy Green]

I have a situation where I have several different input formats that
ultimately need to construct a List<Map<String,Object>> and at some
point I will need to write out the same datatype as well. Classic
serialization.

Maybe what you want is a POD.
See http://mindprod.com/jgloss/pod.html

I used one called ObjectStore.

See http://mindprod.com/jgloss/objectstore.html

 

[Roedy Green]

The Java Persistence API would likely be useful, too.

Did you mean by that PersistenceDelegate or Preferences?

Preferences stores stuff in the registry is a very fluffy format. So
you don't get the safety of backup of a true database.

See http://mindprod.com/jgloss/persistence.html
http://mindprod.com/jgloss/preferences.html

 

[Lew]

Did you mean by that PersistenceDelegate or Preferences?

No, neither.

Preferences stores stuff in the registry is a very fluffy format. So
you don't get the safety of backup of a true database.

Not what I was discussing.

See http://mindprod.com/jgloss/persistence.html
http://mindprod.com/jgloss/preferences.html

I'm talking about

 

[Daniel Pitts]

The Java Persistence API would likely be useful, too.

Hibernate 3.20 is a superset of the Java Persistence API.

 

[Sideswipe]

Yes, well I would love to go to Hibernate but unfortunately I am
dealing with legacy code and no one has any experience with hibernate
but me. It's frustrating. Also, the data doesn't necessarily come from
a database. It may come from a config file or XML

 

[Daniel Pitts]

Yes, well I would love to go to Hibernate but unfortunately I am
dealing with legacy code and no one has any experience with hibernate
but me. It's frustrating. Also, the data doesn't necessarily come from
a database. It may come from a config file or XML

Well, Hibernate doesn't prevent you for loading for elsewhere.

In any case, I find it useful to separate out the reading/writing from
the type itself. There are JavaBean serializers that will write/read
XML (I think they're standard). Or you can write your own DAO (Data
Access Object). Many people associate DAO's with databases, but it is
just as appropriate for file-stored data. You would have a different
implementation of the DAO for DB vs Config vs XML.

Hope this helps,
Daniel.