Fix check for primitive return types

[yuppie-flu]

The current version of Baigan assumes that the return type of any configuration key MUST NOT be a primitive type (e.g. int, boolean in Java). One must use wrapper types instead (e.g. Integer, Boolean, etc.)

The library contains a check to validate this on Spring Context initialization. However, the validation code contains a bug:

 if (value.getClass().isPrimitive())

value here is already an object of type java.lang.Class for majority of the cases, including for primitive types. value.getClass() return a class for java.lang.Class itself, not the class for int or boolean for example.

The fix changes the expression to:

if (value instanceof Class && ((Class<?>)value).isPrimitive())

Also the PR moves the validation check to the ConfigurationBeanDefinitionRegistrar class to make the error message from the thrown exception appears during Spring Context initialization. When the check is located in BaiganConfigClasses, Spring hides the exact error message in a generic Spring Context initialization message.

[lukasniemeier-zalando]

👍