How to apply Single annotation on multiple variables?

Question

I am rookie in Java Annotation and have been searching for applying single annotation on multiple variable simultaneously.

Code:

Answer 1

@NotNull annotation can be applied at element not at group of elements.

JavaDoc: The annotated element must not be null. Accepts any type.

If you really want to get away with boiler plate code, you can use frameworks like Lombok which can help you to certain extent.

Link : http://projectlombok.org/features/Data.html

OR you can use reflection to validate all the method.

for (Field f : obj.getClass().getDeclaredFields()) {
  f.setAccessible(true); // optional
  if (f.get(obj) == null) {
     f.set(obj, getDefaultValueForType(f.getType()));
     // OR throw error
  }
}

Answer 2

Java does not support multiple annotation of this type. But you can write something like this

• Create a class with annotated field.
• Create setters and getters to access the field.
• Create all your name,email field as instance of this class.

This way fields will implicitly annotated as NotNull.

            public class NotNullString {
                @NotNull
                String str;
                public void set(String str)
                {
                    this.str = str;
                }
                public String get()
                {
                    return this.str;
                }
            }

            NotNullString name;
            NotNullString email;