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Subject: Re: Vaadin Integration and MetaData of mappings
From: Andrus Adamchik <andrus@objectstyle.org>
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 <CAFrHPLFZhbUDcksBGHb2XjPktXmtxR2CYtaWXnZdKuOS9hLXHw@mail.gmail.com>
Date: Thu, 30 Aug 2012 07:54:54 +0300
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To: user@cayenne.apache.org

1. Serialization. There's not much to it really. Just make sure the =
context you are using is session-scoped. See for instance this class =
that provides a session-bound context (used by CayenneFilter) :

=
http://svn.apache.org/viewvc/cayenne/main/branches/STABLE-3.1/framework/ca=
yenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/configuration/we=
b/SessionContextRequestHandler.java?view=3Dmarkup

2. Multi-tenancy... So if you go with DB-schema per tenant, it might =
look like this:=20

// do it once per tenant, and cache the returned runtime in the app =
scope
ServerRuntime createServerRuntime(final String tenantSchema) {

   // "cayenne-xyz.xml" is a mapping common to all tenants, that will be =
further customized here
   ServerRuntime runtime =3D new ServerRuntime("cayenne-xyz.xml", new =
Module() {

        // in a custom module override the schema of all loaded DataMaps
        public void configure(Binder binder) {
             binder.bind(DataMapLoader.class).toInstance(new =
TenantMapLoader(tenantSchema));
        }
   });
    =20
   =20
   return runtime;
}

class TenantMapLoader extends XMLDataMapLoader {

    private String tenantSchema;

    TenantMapLoader(String tenantSchema) {
        this.tenantSchema =3D tenantSchema;
    }


    public DataMap load(Resource configurationResource) {
         DataMap map =3D super.load(configurationResource);
         map.setDefaultSchema(tenantSchema);
       =20
         for(DbEntity e : map.getDbEntities()) {
             e.setSchema(tenantSchema);
         }
        =20
         return map;
    }
}

Andrus


On Aug 29, 2012, at 4:15 PM, Juan Jos=E9 Gil wrote:

> Thanks for the reply Andrus!
>=20
> Could you point me to docs/samples about ObjectContext Serialization &
> multi-tenant approaches you describe?
>=20
> About the"adding-metadata" part, I was thinking in adding constraints =
in a
> similar way to active-record in RoR or GORM in grails, but using code
> generation phases of cayenne.
>=20
> By now i'll use some kind of "typed" KVC delegating to cayenne the
> properties access and then providing some kind a "class metadata" =
which can
> be extended by subclasses... but i'll prefer the "code generation" =
form, so
> I can use IDEs capabilities.
>=20
> maybe I'll generate some "java code configuration" which then will be =
used
> to generate final classes... it sounds as a mess but it could give =
really
> nice possibilities! don't you think?
>=20
> if i get to somewhere with this approach I'll tell you :)
>=20
>>=20
>>=20
>>> the data objects will reside at the http session, and will be used
>> directly by the vaadin widgets, does this kind of cayenne data =
objects
>> "use" could arrive with attaching/detaching problems?
>>=20
>> Shouldn't be a problem. You can store Cayenne objects in a session. =
The
>> simplest way to avoid attach/detach issues is to have a =
session-scoped
>> ObjectContext. Then it is serialized/deserialized together with the =
objects
>> in case the session is saved to disk, or replicated across the =
cluster.
>>=20
>>> Also, is there a way to add metadata info in cayenne metamodel? I =
would
>> like to add constraints / validations to generated classes, so they =
can be
>> used to define searching criterias on indexed attributes (something =
like
>> active-records class filters, but only on indexed properties) and =
generate
>> model validations on properties so they can be used at UI fields =
directly,
>> facilitating the app development.
>>=20
>> You can add extra info using callbacks or lifecycle listeners. Any =
extra
>> properties can be defined either manually in generated subclasses, or =
even
>> stored in the base CayenneDataObject (with 'readProperty' / =
'writeProperty'
>> methods, and custom property names).
>>=20
>>> Finally, I'm looking for a multitenant implementation to use, and I
>> believe that the solution pointed at
>> =
http://blog.jerodsanto.net/2011/07/building-multi-tenant-rails-apps-with-p=
ostgresql-schemas/could be also used with cayenne; is there any =
constraint I should look for?
>>=20
>> Cayenne is certainly friendly to various multi-tenancy approaches. In =
3.1
>> API terms, you might assign a separate instance of ServerRuntime to =
each
>> tenant, and use that to create ObjectContexts for its users. You may =
start
>> all runtimes from the same basic configuration, and "namespace" them =
using
>> tenant-unique DB URL. Or you may use a single DataSource, and after a
>> runtime is loaded, scan through all its DbEntities and assign a =
tenant
>> "schema" to them. Feel free to ask about further details.
>>=20
>> Andrus
>>=20
>>=20
>> On Aug 26, 2012, at 5:15 PM, Juan J. Gil wrote:
>>> Hello, I'm thinking to use cayenne in conjunction with vaadin (
>> http://vaadin.com).
>>>=20
>>> I'm trying to use some kind of tight integration between both =
frameworks
>> (defining cayenne generated classes which are vaadin data models
>> implementations).
>>> That way I could define forms directly on data objects, querying &
>> mutating its state directly from vaadin widgets.
>>> As vaadin is an stateful web framework, should I have to expect for =
some
>> kind of problem with data objects between requests? I mean, the data
>> objects will reside at the http session, and will be used directly by =
the
>> vaadin widgets, does this kind of cayenne data objects "use" could =
arrive
>> with attaching/detaching problems?
>>>=20
>>> Also, is there a way to add metadata info in cayenne metamodel? I =
would
>> like to add constraints / validations to generated classes, so they =
can be
>> used to define searching criterias on indexed attributes (something =
like
>> active-records class filters, but only on indexed properties) and =
generate
>> model validations on properties so they can be used at UI fields =
directly,
>> facilitating the app development.
>>>=20
>>> Finally, I'm looking for a multitenant implementation to use, and I
>> believe that the solution pointed at
>> =
http://blog.jerodsanto.net/2011/07/building-multi-tenant-rails-apps-with-p=
ostgresql-schemas/could be also used with cayenne; is there any =
constraint I should look for?
>>>=20
>>> Best regards
>>> Juanjo
>>>=20
>>> ps: pardon my really poor English! :P
>>>=20
>>>=20
>>=20
>>=20