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From Marcel Offermans <marcel.offerm...@luminis.nl>
Subject Re: Client REST API
Date Wed, 07 Aug 2013 15:43:05 GMT
Hello Elmar,

On Aug 7, 2013, at 12:50 , Elmar Zeeb <elmar.zeeb@pipesbox.de> wrote:

> thank you for your fast response! Reading your response i realized that i forgot some
points in my last mail.
> 
> Am 06.08.2013 14:37, schrieb Marcel Offermans:
>> 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 didn't mention that my client can't run inside apache ace, but should use a remote
api.

The client.jar is something that can be run completely separate (and remote) from the server.
We actually run it on our build agent.

> The next point is, that i can't use osgi to run the client.

The client does use OSGi. I'm sure you can always embed OSGi inside a normal application.

> From my explorations the java client api can run remotely but depends on osgi. That's
why i looked at the REST API first.

Correct.

>>> 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 athttps://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=&right=query. 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=[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=foo)", "(id=bar)");
> I setup the ace rest client to run in a debugger and found out, that setting "leftEndpoint"
and "rightEndpoint" attributes during association creation does not work. The associations
are created successfully but the ldap filters are not used to associate resources. That may
be the cause why the vaadin ui doesn't show this associations.

I'd have to look into that, because that might be a bug.

> Now I set "left" and "right" attributes. If I use ressource ids for left and right ace
automatically fills in corresponding ldap filters for leftEndpoint and rightEndpoint. So setting
leftEndpoint and rightEndpoint attributes directly doesn't seem to work.

Ok.

>> 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.
> My programmatically created associations with leftEndpoint and rightEndpoint attributes
don't show up in the vaadin ui, but associations with left and right attributes show up in
the vaadin ui - problem solved.

Ok.

>>> ACE-151 mentions that there are no checks for LDAP filters so the filter may
not work.
>>> 
>>> 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.
> So now I have a working client for 1:1 associations as I can read the left and right
attribute of associations. But when I use 1:n associations i can't easily get the list of
related objects - besides using the java api. I'm looking for query similar to getLeft() and
getRight() in the REST API. Is there something similar? Or does the left and right attribute
contain a list of resource ids in this case ?

From memory I don't think we created REST calls to retrieve such lists yet. It would be a
valid enhancement request though.

> When i was debugging the rest api i also saw that the target resource as special operations:
register and approve.
> I can imagine what these operations do, but how do i call them ?

From the code, by doing a POST on:
workspaceID/entityType/entityID/action

> At the moment i register a target by recreating a target resource and unregister the
a target by deleting a target resource. But i have no way to approve changes without setting
the auto approve attribute.

That's what the approve operation above was for. If you have more things you'd like to do,
but can't (figure out) please do keep asking and suggesting features.

Greetings, Marcel


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