[Registry-dev] Restricted collections

[Chathura C. Ekanayake]

Current handler implementation allows users to write handlers to 
restrict the allowed child media types of collections. Axis2 repository 
collection is an example of such collection. I think this is a frequent 
use case, where users would like to configure collections on the fly 
using the UI. We can introduce some UI controls and API methods to 
support this functionality. First, from the API side, we can have below 
methods in the Collection interface.

void setChildPolicy(String policy);

String getChildPolicy();

void addChildMediaType(String mediaType);
   
void removeChildMediaType(String mediaType);

String[] getChildMediaTypes();

Below are the allowed values for child policy.

ALLOW_ALL --> No restriction (normal collection).
ALLOW_SELECTED --> Only allow the selected media types given from 
addChildMediaType(...) method.
DENY_SELECTED --> Only deny the selected media types given from 
addChildMediaType(...) method.

Then you can have a collection with only xml files by calling below methods.

Collection c = registry.newCollection();
c.setChildPolicy(Collection.ALLOW_SELECTED);
c.addChildMediaType("application/xml");
registry.put("/projects/config", c);

On the UI side, we can provide some UI controls in the collection's page 
to set the child policy and child media types.

Thoughts...

Thanks,
Chathura