Re: [OJB-developers] Ojbgen code generator

[Thomas M. <tho...@ho...>]

Hi Hoang,

Hoang, Hai wrote:

> I've some code that read the repository.xml 


Reading a repository.xml is done by 
ojb.broker.metadata.RepositoryPersistor. I see no reason to duplicate 
this functionality. If your code uses the RepositoryPersistor, OK! If 
not please refactor it to use the RepositoryPersistor.

> and generate java code 


That's interesting. You are generating code from a 
ojb.broker.metadata.DescriptorRepository or directly from the parsed 
repository.xml file?

If you are generating from DescriptorRepository you solution could be 
the step towards the OJB code genartor stuff!

Are you using a special library for code generation, or do you generate 
Java code manually?
I'd prefer using an existing opensource library!

> for the
> following pattern from previous project (ATG) and now I want to port over to
> OJB and donate it to the ojb community.
> 



thanks!


> For example, if I have a class descriptor and these are classes will be
> generated:
> 
> User (interface)
> UserImpl (class)
> UserManager (interface)
> UserManagerImpl (class)
> 


IMO there should be some kind of template mechanism to allow 
user-defined generation schemes. Generating those for classes may be 
perfect for your environment. But others would like different schemes.
In my company we use:
User (interface)
UserBaseImpl implements User (abtract class, only getters and setters 
are implemented)
UserImpl extends UserBaseImpl (all other methods are implemented here)
UserHome (factory class)

We should not force OJB use to use a specific generation scheme.


> 1.  I would like to know, which class parses the repository.xml for
> information purposes only (without validation), so I can use the information
> in the repository to generate code.


Have a look at ojb.broker.metadata.RepositoryPersistor. This guy builds 
up the DescriptorRepository from a repository.xml (and in the near 
future from a repository.jdo) file.
BUT:it uses validation! (I don't understand why you do not to use XML 
validation???)


> 
> 2.  Can we possibly add a
> <interface.name>com.xyz.Permission</interface.name> tag to the class
> descriptor along with <class.name>com.xyz.PermissionImpl</class.name>?
> 


There is already a mechanism to define interface based extends in the 
repository. For example there is an extent declaration for 
"InterfaceArticle" in our junit testsuite repository_junit.xml declaring 
all implementations of this IF.
This could also be used to get your required information

The DescriptorRepository is meant for object/relational mapping 
information. Metainformation related to codegeneration patterns should 
be kept in a separate place.
The best way (as mentioned above) would be to provide a template 
mechanism to allow maximum flexibility.


> 3.  Can I reuse the metadata package to store the parsed information from
> the repository.xml without required runtime classes? for example, if I have
> a <class.name>com.xyz.PermissionImpl</class.name> in one of my class
> descriptor and the file is not yet genereated, will this causes me problem?
> 


Oops, you got me! This is an aspect I did not think about before! In 
fact the current DescriptorRepository relies on existing persistent 
classes. There are several places where the XmlRepositoryHandler tries a 
Class.forName(...), which will cause a lot of exceptions in the case you 
are describing. The same holds true for attribute fields (or 
getter/setter methods if you are using bean access).

But it should not be too difficult to change this.
A ClassDescriptor should be marked with a special tag saying "this class 
could not be found and should be generated".

cheers,

Thomas


> Thank you,
> 
> Hai
> 
> 
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