Hi Peter,
Glad Cayenne worked out well for you and thanks for sharing Derby
experience.
On Sep 8, 2006, at 5:20 PM, Peter Karich wrote:
If I create a new object, can I query the database (e.g. a
SelectQuery) without a commit? I tried this, but it does not work?
Should'nt I get this object from the cache instead of the db if it
is new?
No you can't, as all queries (except for ObjectIdQuery) are not
matched against individual objects in the cache. Doing it otherwise
would turn Cayenne into RDBMS itself :-) If this is really important,
there are workarounds involving external transactions. If you really
need that and ready to jump a few hoops, we can discuss the details.
How to get the available column headers, not only the headers which
I defined in the modeler? (I wanted that users of gstpl can change
the columns of my tables from within gstpl.)
I tried SelectQuery select = new SelectQuery(tableName);
QueryMetadata meta = select.getMetaData(getContext
().getEntityResolver());
Iterator iter = meta.getDbEntity().getAttributes().iterator();
colDefinition = new HashSet();
while(iter.hasNext()) colDefinition.add(((DbAttribute)iter.next
()).getName());)
You are on the right track here. The only change - you need to map
ALL table columns in the DbEntity, but only map a subset of them in
the ObjEntity.
What could happen if I make a raw sql update statement? (Docs says:
'... and therefore may potentially leave object graph in an
inconsistent state.') What does this mean for me as programmer?
It means stale data. E.g.:
// initial object state
assertEquals("a", myArtist.getName());
// run "update artist set name = 'b' where name = 'a'"
// this will fail, as the artist name is still 'a' in memory
assertEquals("b", myArtist.getName());
What you can do is DataContext.invalidateObjects() if you can guess
which artists are affected. Also 3.0 release introduces a
RefreshQuery [1] that allows to invalidate groups of objects. Though
3.0 is not yet released, and you'd have to build it yourself from SVN.
Does cayenne support user management in any sense?
No.
Why or when should I use 'Remote Object Persistenc'? (Sorry for
that newbie question ...)
Most common scenario are desktop (Swing or SWT) apps that should not
or can not access the DB directly.
Which license-agreement-files should I add for gstpl? (it only uses
the cayenne.jar)
Each release contains a Cayenne license file (and licenses for all
dependencies) that you need to include with the distribution of any
Cayenne-based software. In 1.2 the licenses are located under
"cayenne_install_dir/docs/licences/" directory. Since you do not
distribute the modeler, you'll need "LICENSE" and "LICENSE.apache"
files.
Last but not least: How do you earn money with cayenne?
If anybody knows the answer to this question, I'd like to know too :-)
Seriously, most folks who are involved in development (myself
included) are software consultants using Cayenne as a part of the
stack when implementing solutions for their customers. Second common
way (that is also a variety of consulting) is training and support
for the framework.
I guess a self-plug is due here - yes sometimes I do charge money to
solve Cayenne problems :-)
[1] http://cwiki.apache.org/confluence/display/CAY/RefreshQuery
Andrus
