[REEF-967] Handle null in RequiredImpl

• Type: Sub-task
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.16
• Component/s: Tang
• Assignee: Ji Eun Lee
• Reporter: Sergey Dudoladov
• Created: 18/Nov/15 09:36
• Updated: 03/Aug/16 18:26
• Resolved: 03/Aug/16 18:26

Description

Setting RequiredImpl to null should throw an informative exception instead of NPE.

To reproduce, in the TestConfigurationModule set the RequiredImpl<TestConfigurationModule.Foo> THE_FOO to null:

 String s = null;
 MyConfigurationModule.CONF
         .set(MyConfigurationModule.THE_FOO, s)
         .build();

This code raises java.lang.NullPointerException in org.apache.reef.tang.util.ReflectionUtilities.classForName(ReflectionUtilities.java:170)