Reflection /is/ supported, with limitations.
According to: http://code.google.com/appengine/docs/java/runtime.html#The_Sandbox
:
Reflection
An application is allowed full, unrestricted, reflective access to its
own classes. It may query any private members, use
java.lang.reflect.AccessibleObject.setAccessible(), and read/set
private members.
An application can also also reflect on JRE and API classes, such as
java.lang.String and javax.servlet.http.HttpServletRequest. However,
it can only access public members of these classes, not protected or
private.
An application cannot reflect against any other classes not belonging
to itself, and it can not use the setAccessible() method to circumvent
these restrictions.
JDBC is not supported. The data store isn't based on a relational
database; it's an object-oriented data store.
From:
http://groups.google.com/group/google-appengine-java/web/will-it-play-in-app-engine?pli=1
"Java Database Connectivity (JDBC)
Not supported - the App Engine datastore is not a relational store.
Use JDO or JPA instead."
That said, we could still /probably/ provide a db adapter for the app
engine store, and instead of translating queries, etc. to sql,
translate them to the appropriate api calls.
I suppose, in theory, you could write a jdbc adapter that translates
SQL to the appropriate api calls, but... that seems a little silly. :)
The "dbadapter" approach is better, I think.
Robert
On Apr 10, 2009, at 4/1012:40 PM , Mike Kienenberger wrote:
From what I understand, it's not JDBC that's not supported, but the
lack of a Google Apps Engine JDBC driver.
I haven't tried it, but it seems like it'd be easy enough set up.
Yes, reflection isn't supported.
Again, though, I think the real fitting point is not getting Cayenne
to run in entirety on the app engine as a java -> javascript
translated byte code, but to make sure that client-side ROP works on
the apps engine, with Cayenne running on the server-side.
On Fri, Apr 10, 2009 at 10:47 AM, Andrus Adamchik
<[email protected]> wrote:
On Apr 10, 2009, at 5:36 PM, Joseph Schmidt wrote:
Can cayenne run on the new Google AppEngine/Java?
I'm asking this because there are quite some restrictions to the
applications that work, and many known frameworks don't work (but
the
authors promised to make them work - e.g. Tapestry):
http://groups.google.com/group/google-appengine-java/web/will-it-play-in-app-engine
e.g. Hibernate does not work (maybe this might be the chance for
Cayenne
to get some more publicity if it could work :) ?).
thanks,
Joseph.
A good question...
IIRC Google apps engine does not support JDBC? So that will be a
showstopper, although the stack is abstracted well enough so that
it should
be possible to re-implement a non-JDBC DataNode. Otherwise Cayenne
does not
rely on reflection for CayenneDataObjects, and should be possible
to port
... I think.
maybe this might be the chance for Cayenne to get some more
publicity if
it could work :) ?).
This might also be a chance for new Cayenne volunteers to get
publicity ;)
Andrus
