Annotatiomania™ in Struts 2.0

I have to admit, I have not made any experience with Struts 1.0. Neither with 2.0. From what I understand, Struts 2.0 tried to move away from XML to use annotations instead. Just like Hibernate/JPA did. They have published Struts 2.0 with this title:

Apache Struts 2 is an elegant, extensible framework for building enterprise-ready Java web applications.”

Elegant… ELEGANT! My untrained eye must be oblivious of some relevant facts. But can anyone explain to me what’s so elegant about the following code block (I can see how it is “extensible”, though)?

@Validation()
public class SimpleAnnotationAction extends ActionSupport {

    @RequiredFieldValidator(type = ValidatorType.FIELD, message = "You must enter a value for bar.")
    @IntRangeFieldValidator(type = ValidatorType.FIELD, min = "6", max = "10", message = "bar must be between ${min} and ${max}, current value is ${bar}.")
    public void setBar(int bar) {
        this.bar = bar;
    }

    public int getBar() {
        return bar;
    }

    @Validations(
            requiredFields =
                    {@RequiredFieldValidator(type = ValidatorType.SIMPLE, fieldName = "customfield", message = "You must enter a value for field.")},
            requiredStrings =
                    {@RequiredStringValidator(type = ValidatorType.SIMPLE, fieldName = "stringisrequired", message = "You must enter a value for string.")},
            emails =
                    { @EmailValidator(type = ValidatorType.SIMPLE, fieldName = "emailaddress", message = "You must enter a value for email.")},
            urls =
                    { @UrlValidator(type = ValidatorType.SIMPLE, fieldName = "hreflocation", message = "You must enter a value for email.")},
            stringLengthFields =
                    {@StringLengthFieldValidator(type = ValidatorType.SIMPLE, trim = true, minLength="10" , maxLength = "12", fieldName = "needstringlength", message = "You must enter a stringlength.")},
            intRangeFields =
                    { @IntRangeFieldValidator(type = ValidatorType.SIMPLE, fieldName = "intfield", min = "6", max = "10", message = "bar must be between ${min} and ${max}, current value is ${bar}.")},
            dateRangeFields =
                    {@DateRangeFieldValidator(type = ValidatorType.SIMPLE, fieldName = "datefield", min = "-1", max = "99", message = "bar must be between ${min} and ${max}, current value is ${bar}.")},
            expressions = {
                @ExpressionValidator(expression = "foo > 1", message = "Foo must be greater than Bar 1. Foo = ${foo}, Bar = ${bar}."),
                @ExpressionValidator(expression = "foo > 2", message = "Foo must be greater than Bar 2. Foo = ${foo}, Bar = ${bar}."),
                @ExpressionValidator(expression = "foo > 3", message = "Foo must be greater than Bar 3. Foo = ${foo}, Bar = ${bar}."),
                @ExpressionValidator(expression = "foo > 4", message = "Foo must be greater than Bar 4. Foo = ${foo}, Bar = ${bar}."),
                @ExpressionValidator(expression = "foo > 5", message = "Foo must be greater than Bar 5. Foo = ${foo}, Bar = ${bar}.")
    }
    )
    public String execute() throws Exception {
        return SUCCESS;
    }
}

Taken from the docs, here: http://struts.apache.org/2.x/docs/validation-annotation.html. Thanks to Sergio for sharing this link. I guess you can actually put Java code in annotation strings, that is compiled at run-time using some Eclipse compiler or something… Who knows? :-)