Validation error: “No validator could be found for type: java.lang.Integer”

As per the javadoc of NotEmpty, Integer is not a valid type for it to check. It’s for Strings and collections. If you just want to make sure an Integer has some value, javax.validation.constraints.NotNull is all you need.

public @interface NotEmpty

Asserts that the annotated string,
collection, map or array is not null
or empty.