[jira] [Created] (CAY-1752) Java type should be a property of DbAttribute, not ObjAttribute

["Andrus Adamchik (JIRA)" <ji...@apache.org>]

Andrus Adamchik created CAY-1752:
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             Summary: Java type should be a property of DbAttribute, not ObjAttribute
                 Key: CAY-1752
                 URL: https://issues.apache.org/jira/browse/CAY-1752
             Project: Cayenne
          Issue Type: Improvement
          Components: Core Library
            Reporter: Andrus Adamchik
            Assignee: Andrus Adamchik
             Fix For: 3.2M1


from here: http://markmail.org/message/icr7seqazgsdtewc

I am thinking of redefining one of the mapping assumptions that was in Cayenne
since day one. In 3.2 I want to move attribute java type from ObjAttribute to
DbAttribute. The goal of this change is to improve consistency of the runtime
model. Current separation of Java and DB attribute types causes a whole class of
bugs and a whole class of hacks in the framework.

E.g.:

1. Unrecognized non-standard type mapping. This one is discussed at the moment
on the user list [1]. I suspect it has nothing to do with "custom" types, but
rather with non-JDBC default mapping of DB data to Java, regardless of the Java
type.

2. Hacks to recognize non-standard type mapping. When creating a DataRow,
Cayenne would try to guess which ObjEntities might use this DataRow, and
populate DataRows with values corresponding to the ObjAttribute type
definitions. This clearly breaks layer separation - lower layers have to know
too much about the higher layers of the stack. Besides it doesn't always work
anyways - see #3.

3. Extra mapping "flexibility" that doesn't really work. We had past Jiras when
the same column is mapped to different Java types in 2 different subclasses,
creating a mess in subclass-agnostic DataRows.

This is not a full list of problems, but gives you some idea. I am hoping the
suggested change would tie things up and leave no space for ambiguities. 

[1] http://markmail.org/message/6bs2suislyfp3apk

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