[REEF-968] Handle RequiredParameter set to null

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Not A Problem
• Fix Version/s: 0.16
• Component/s: Tang
• Assignee: Unassigned
• Reporter: Sergey Dudoladov
• Created: 18/Nov/15 09:50
• Updated: 10/Aug/16 21:03
• Resolved: 10/Aug/16 21:03

Description

Attempt to set a RequiredParameter to null should probably use a default value if available or throw a meaningful exception.

To reproduce, see the comment to REEF-932

I modified that patch to include the default value for

@NamedParameter(default_value = "abc")
  class FooStringness implements Name<String> {
  }

but that code also throws IllegalStateException.

We probably should use the default value instead and log (a) the warning that the RequiredParameter is set to null (b) the default we use.