Spring mvc verification recommendations

Question

I am learning myself Spring MVC 2.5 mainly from the docs. Can someone explain the following:

• Advantages / Differences in Using command Objects Compared to Using @ModelAttribute to @ModelAttribute in an Object.
• Is there an easier way to do validation and then write a Validator object?

Also, in this code, how does the line ValidationUtils.rejectIfEmpty(e, "name", "name.empty"); ? How can he check if a person’s name is empty when the person’s object is not transferred?

  public void validate(Object obj, Errors e) { ValidationUtils.rejectIfEmpty(e, "name", "name.empty"); Person p = (Person) obj; if (p.getAge() < 0) { e.rejectValue("age", "negativevalue"); } else if (p.getAge() > 110) { e.rejectValue("age", "too.darn.old"); } } 

(this code is from section 5.2 of the documents )

thanks

Answer 1

Here is the answer to your first question. http://chompingatbits.com/2009/08/25/spring-formtag-commandname-vs-modelattribute/

according to my experience, there is no simpler way to authenticate because it is easy enough. You can simplify the integration of libraries, such as commons-validator, into your project, and use predefined validation rules in your forms.

http://numberformat.wordpress.com/tag/spring-mvc-validation/

as well as with the third version of Spring, you can use Bean validation with annotations.

Answer 2

• The issue of the command object is not very clear. If you mean the following syntax

   @RequestMapping(...) public ModelAndView foo(Command c) { ... } 

  then this is the same as

   @RequestMapping(...) public ModelAndView foo(@ModelAttribute Command c) { ... } 

  because @ModelAttribute can be omitted. The only case when this is really necessary is that you need to explicitly specify the attribute name (otherwise it would be displayed as a class name with the first decapitalization of the first letter, i.e. command )

• In Spring 2.5, no. In Spring 3.0, you can use declarative validation using the JSR-303 Bean validation API.

• The Errors object has a reference to the object being checked.