The OData Unmarshaller should be able to set value to null when the Xml set the value to null.

[guangyang]

Moved from https://github.com/WindowsAzure/azure-sdk-for-java-pr/issues/463.
Dev Estimate: 3
Test Estimate: 0

In create job request, when the templateId is not used, the server sets the value to null, but the JobInfo created with value empty string.

<d:TemplateId m:null="true"/>

[gcheng]

the problem happens at the OData unmarshaller

[gcheng]

in Java, empty string and null string are often used interchangably. Not worthy the effort to fix it.