---------- Forwarded message ----------
From: Clinton Begin <[EMAIL PROTECTED] >
Date: May 29, 2005 9:56 AM
Subject: Re: Support for generics
To: Nathan Maves <[EMAIL PROTECTED]>
I understand that that is possible. I'm personally not a fan of code generation at all. In this case I think it would be especially impractical. I've never just sat down and coded all of my SQL mapping files up front, which would be necessary if we were to generate the interface. I suppose we could regenerate it after each change, but what a yucky programming paradigm. By the time we've set up the Ant build, the SQL Mapper interface generator task, and all of our SQL Maps, I could have typed a lot of interfaces!
I think one of the best benefits of this approach is that you can very easily test drive your persistence layer.
You can start with a test:
public void testShouldGetDocumentWithIDofOne () {
DocumentMapper mapper = new MockDocumentMapper(); //or use your favourite mocking framework
Document doc = mapper.getDocument(i);
assertNotNull (doc);
assertEquals (1, doc.getId());
}
You can create the interface and the mock:
public interface DocumentMapper {
Document getDocument (int id);
}
public class MockDocumentMapper implements DocumentMapper {
public Document getDocument (int id) {
return new Document (id);
}
}
All without an SqlMapClient. Of course all we're really testing in this example is an interface, but what this allows you to do is more easily test of consumers of the mapping layer (DAOs). For example, if you have a DAO that depends on a Mapper, you can more easily test the DAO without an SqlMapClient instance (or any persistence related mocks):
public class SqlMapDocumentDao extends SqlMapDaoTemplate {
private DocumentMapper documentMapper;
// Used by the DAO framework
public SqlMapDocumentDao (DaoManager daoManager) {
super(daoManager);
// this next method isn't part of the DAO template yet
documentMapper = (DocumentMapper) getMapper(DocumentMapper.class);
}
// Used by unit tests
public SqlMapDocumentDao (DocumentMapper documentMapper) {
this.documentMapper = documentMapper;
}
}
I know it looks like a lot of code, and indeed we'd want to question the value of using both DAO and Mapper interfaces (too much abstraction). The testing approach described above works just as well at the service layer (i.e. without DAOs), or even at the presentation layer (i.e. without a service layer -spank!). I think this gives us a cleaner alternative model for when we don't use DAOs, and a more layered model if we want maximum abstraction (limited value, but it's there).
If I were to ditch a layer in this 5 layer cake, I'd ditch the DAOs. :-)
Cheers,
Clinton
On 5/28/05, Nathan Maves <[EMAIL PROTECTED]
> wrote:
Clinton,
First off thanks. I will get it a go this week.
As per Fabrizio response to the email below, I agree that this process
of creating interfaces is too programatic. By that it would seem to me
that these interfaces could be created automatically when parsing the
sql map files. All you would need to do is create a method based on
the id, resultClass and the parameterClass.
Am I way of in thinking this?
Nathan
On May 28, 2005, at 10:36 PM, Clinton Begin wrote:
>
> http://www.mail-archive.com/ibatis-user-java@incubator.apache.org/
> msg02403.html
>
> Cheers,
> Clinton
>
> On 5/28/05, Nathan Maves < [EMAIL PROTECTED]> wrote:
>> to use the Mapper binding functionality.
>>
>> Nathan
>>
>> On May 27, 2005, at 8:32 PM, Clinton Begin wrote:
>>
>> >
>> >I believe the new Mapper binding functionality would resolve
>> this....
>> >
>> >Nathan, are you up for trying it out?
>> >
>> >Cheers,
>> >Clinton
>> >
>> >
>> > On 5/27/05, Nathan Maves < [EMAIL PROTECTED]> wrote:
>> >> gets to the DAO layer.
>> >>
>> >> You can cast the List but you will always get the warning for and
>> >> unchecked assignment when the List is returned from the sqlmap.
>> >>
>> >> List<Student> students = (List<Student>)executeQueryForList
>> >> ("getStudents",null);
>> >>
>> >> Looks good but does not resolve the warnings.
>> >>
>> >> Nathan
>> >>
>> >>
>> >> On May 27, 2005, at 2:30 PM, Larry Meadors wrote:
>> >>
>> >> > I have done that with my DAO layer.
>> >> >
>> >> > SqlMap returns it as List, but you can cast it.
>> >> >
>> >> > Worked great. :)
>> >> >
>> >> > Larry
>> >> >
>> >> >
>> >> > On 5/27/05, Nathan Maves < [EMAIL PROTECTED] > wrote:
>> >> >
>> >> >> Since apple is taking then sweet time I just got Java 1.5.I am
>> >> >> diving in head first but I am curious about what the plans for
>> >> >> Generics are.
>> >> >>
>> >> >> Will I batis support them?
>> >> >> Could there be a way to specify the list type instead of Object?
>> >> >>
>> >> >> i.e.
>> >> >> return a List<Student> back based on the result class of the
>> query?
>> >> >>
>> >> >> Nathan
>> >> >>
>> >> >>
>> >> >
>> >>
>>
