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Subject: Re: Client REST API
From: Marcel Offermans <marcel.offermans@luminis.nl>
In-Reply-To: <5200DBD2.40706@pipesbox.de>
Date: Tue, 6 Aug 2013 14:37:10 +0200
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Message-Id: <92DF3132-68C9-41E8-B6A1-C3B7591EC402@luminis.nl>
References: <5200DBD2.40706@pipesbox.de>
To: <users@ace.apache.org>

Hello Elmar,

On Aug 6, 2013, at 13:19 , Elmar Zeeb <elmar.zeeb@pipesbox.de> wrote:

> i'm looking into apache ace to check if i can use it as backend for a =
web based market to install software extensions on an osgi based =
application. In this use case i can't use the vaadin based ui but =
started to implement a java based client for the client REST API.

Underneath the Vaadin, REST and (very recently) GoGo client API's lies =
the same Java Client API. In other words, that's a good place to start =
with your own client. In this case, the "Workspace" class that is an =
abstraction on top of that (part of the REST client) can be used to =
start.

> I'm aware of the amdatu ace client, but i wanted to implement a client =
on my own to understand the api and apache ace. Currently i'm able to =
create, modify and delete different client resources (artifact, feature, =
distribution and target) but have problems with associations. I have =
looked at the client rest api docu on ace.apache.org and at =
https://issues.apache.org/jira/browse/ACE-151 to get a better =
understanding of associations filters and queries.

Ok.

> I don't understand how to set the leftEndpoint and rightEndpoint =
attributes of associations. As written on the web site these attributes =
are LDAP filters. Does this mean that i have to parse the LDAP filter on =
the client side to check which resources are associated?

Yes, they are LDAP filters.
No you don't need to parse them yourself, that is something the =
associations will do for you. Just provide the filter condition and it =
will be evaluated against objects on the left or right hand side of the =
association.

> Is there a way to let ace do the filtering and return resource ids? =
I'm aware of the =
ace/clients/tmp/9876/artifact2feature?left=3D&right=3Dquery. Is there =
something like =
ace/clients/tmp/9876/artifact2feature/12345/leftResourceIdsto query all =
left resource ids of an association?

If you create an association, you can set the left and right hand =
filters yourself.

> The vaadin UI uses attribute based LDAP filters to create =
associations. I would like to have static associations based on resource =
ids - so i use LDAP filters like "(id=3D[resource id])" to specify =
endpoints.

Take a look at the Workspace.cas() method (a generic way to create an =
association) where you can do something like:

 ws.cas("distribution2target", "(name=3Dfoo)", "(id=3Dbar)");

Optional arguments to specify the cardinality can be used to force ACE =
to use a 1:1 (or 1:N, N:1 or N:N) cardinality.

> The vaadin ui can't display these associations.

Actually, if you click on some object, it will always highlight =
everything that is associated, even if you do it via these =
programmatically created associations.

> ACE-151 mentions that there are no checks for LDAP filters so the =
filter may not work.
>=20
> So my question is how to specify association endpoints and how to =
query resource ids of associates resources with the client REST API?

My advice is to use the Java API. If you have an Assocation object, you =
can simply ask it to getLeft() or getRight() and you will get a list of =
all associated objects on either side.

Greetings, Marcel