Andrej Sobkowski wrote: > - The form bean itself is a "special data holder" and shouldn't be aware of > how its data is validated. Do you agree?
I'm not sure that I do. I like to think of the ActionForm as a firewall. If it has passes the intial validation, then I know it is "safe" to use, and can passed along to business methods. Generally, objects should have dominion over their own data. Under the current model, the bean is not even passed to the Action until it is validated. The Action may undertake additional validation, usually in collaboration with the business model, but I think it is valid for an ActionForm to know whether it's String values pass some form of "prima facia" validation. There is usually additional validation at the business logic level, but this is different from the type of validation we need on ActionForms -- like did they even enter anything? Could it even be a number? I do believe we should be able to incorporate the XML configuration in to the Struts config, so that it is near the ActionForm bean it validates, but I'm not sure if "primary" validation should be delegated to another object, if that's what you're suggesting. We could definately use more standard, backend validators, but, personally, I would say that the framework object that calls the standard validator with the property in question should be the ActionForm, or a business object, and not the Action or ActionServlet directly. -- Ted Husted, Husted dot Com, Fairport NY USA. -- Custom Software ~ Technical Services. -- Tel +1 716 737-3463 -- http://www.husted.com/struts/ Andrej Sobkowski wrote: > > Hello All, > > I have a set of design considerations/suggestions for the Validation > Framework in Struts. Let me know if I'm totally missing the point. > > I like the whole Validator approach, in particular the XML configuration. I > believe that's the way to go, but I'd like to discuss a few points. > > DISCUSSION: The Validator is quite "linked" to Servlet's stuff > (HttpServletRequest) and to FormBean. If I got it right, currently the > Validator needs a set of parameters to be passed to the ValidatorAction, > including the bean to validate, the Field and some Servlet parameters. > > In a similar way, the validation process is linked to the FormBean > (validate() in FormBean class). > > Shouldn't they be separate? > - The Action should take care of the HTTP stuff while the Validator should > only have knowledge of the bean and the corresponding fields to be > validated. > - The form bean itself is a "special data holder" and shouldn't be aware of > how its data is validated. Do you agree? > > I was thinking at something like the following (pseudo-code): > > * CONFIGURATION file (new DTD for struts-config.xml or separate file) > <action path="/login" > type="com.mycompany.myActionWithValidation" > name="myForm"> > <!-- add validation on myForm's property 'lastName' that will check via > a SizeValidator > that the size of the field is between 1 and 15 chars. If not, the > message will be > returned in the ValidationException (I18N can be added easily) --> > <validation property="lastName" > validator="com.mycompany.SizeValidator" > arg0="1" > arg1="15" > message="Last Name is mandatory and can't be longer than 15 > chars" /> > ... > </action> > > * JAVA CODE > public interface IValidator(Object bean) { > +validate() throws ValidationException; > } > > public class Action { > ... > +addValidator(IValidator val) > +validators(): Iterator // returns an Iterator on all validators for the > action > } > > // Validator that checks if text size is >min and < max (for example). > // It can be easily extended to check int min/max and so on. > public class SizeValidator { > ... // min/max > > public void validate(Object bean) throws ValidationException { > Object value = getPropertyValue(bean); > if (value instanceof String) { > // Check String size > String check = (String)value; > if ((check.length() > maxSize) || > (check.length() < minSize)) { > // Validation failed: throw exception > // with corresponding error message (defined in conf) > throwException(getValidationMessage()); > } > } else { > // Error, wrong class type... > } > } > } > > // Minor changes to ActionServlet > public class ActionServlet { > ... > public void processInitValidatorsForAction(..) { > // By reading the XML configuration file, the ActionServlet will execute a > set of addValidator(..) > // For example, consider the following XML struts-config.xml (DTD to be > modified) > // <action > curAction.addValidator(new SizeValidator("lastName", "1", "15"); > curAction.addValidator(new RegExpValidator("phone", "(999)999-9999"); > ... > } > > // Executes all validators on FormBean(s) for action executed > public ActionErrors processValidate(...) { > Iterator it = action.validators(); > try { > ((Validator)it.next()).validate(formBean); // the validator validates > the form bean only > } catch (ValidationException e) { > Log.debug("Validation failed!", e); > errors.addError(e.getMessage()); // Add multilanguage > } > } > } > > Useless to say, this is only a high-level point of view. It does work on my > prototype (no XML config), but it can be enhanced and optimized in many > ways. I think it's also conceptually pretty close to what is currently done > in the Validator. > > The Validators can be designed as desired. To compare two values, simply > define a validator like CompareValidator(property1, property2, compareRule) > with compareRule = "<", ">",... > > What do you think? > > Thanks. > > Andrej > > _________________________________________________________________ > Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp > > -- > To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> > For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> > > Hello All, > > I have a set of design considerations/suggestions for the Validation > Framework in Struts. Let me know if I'm totally missing the point. > > I like the whole Validator approach, in particular the XML configuration. I > believe that's the way to go, but I'd like to discuss a few points. > > DISCUSSION: The Validator is quite "linked" to Servlet's stuff > (HttpServletRequest) and to FormBean. If I got it right, currently the > Validator needs a set of parameters to be passed to the ValidatorAction, > including the bean to validate, the Field and some Servlet parameters. > > In a similar way, the validation process is linked to the FormBean > (validate() in FormBean class). > > Shouldn't they be separate? > - The Action should take care of the HTTP stuff while the Validator should > only have knowledge of the bean and the corresponding fields to be > validated. > - The form bean itself is a "special data holder" and shouldn't be aware of > how its data is validated. Do you agree? > > I was thinking at something like the following (pseudo-code): > > * CONFIGURATION file (new DTD for struts-config.xml or separate file) > <action path="/login" > type="com.mycompany.myActionWithValidation" > name="myForm"> > <!-- add validation on myForm's property 'lastName' that will check via > a SizeValidator > that the size of the field is between 1 and 15 chars. If not, the > message will be > returned in the ValidationException (I18N can be added easily) --> > <validation property="lastName" > validator="com.mycompany.SizeValidator" > arg0="1" > arg1="15" > message="Last Name is mandatory and can't be longer than 15 > chars" /> > ... > </action> > > * JAVA CODE > public interface IValidator(Object bean) { > +validate() throws ValidationException; > } > > public class Action { > ... > +addValidator(IValidator val) > +validators(): Iterator // returns an Iterator on all validators for the > action > } > > // Validator that checks if text size is >min and < max (for example). > // It can be easily extended to check int min/max and so on. > public class SizeValidator { > ... // min/max > > public void validate(Object bean) throws ValidationException { > Object value = getPropertyValue(bean); > if (value instanceof String) { > // Check String size > String check = (String)value; > if ((check.length() > maxSize) || > (check.length() < minSize)) { > // Validation failed: throw exception > // with corresponding error message (defined in conf) > throwException(getValidationMessage()); > } > } else { > // Error, wrong class type... > } > } > } > > // Minor changes to ActionServlet > public class ActionServlet { > ... > public void processInitValidatorsForAction(..) { > // By reading the XML configuration file, the ActionServlet will execute a > set of addValidator(..) > // For example, consider the following XML struts-config.xml (DTD to be > modified) > // <action > curAction.addValidator(new SizeValidator("lastName", "1", "15"); > curAction.addValidator(new RegExpValidator("phone", "(999)999-9999"); > ... > } > > // Executes all validators on FormBean(s) for action executed > public ActionErrors processValidate(...) { > Iterator it = action.validators(); > try { > ((Validator)it.next()).validate(formBean); // the validator validates > the form bean only > } catch (ValidationException e) { > Log.debug("Validation failed!", e); > errors.addError(e.getMessage()); // Add multilanguage > } > } > } > > Useless to say, this is only a high-level point of view. It does work on my > prototype (no XML config), but it can be enhanced and optimized in many > ways. I think it's also conceptually pretty close to what is currently done > in the Validator. > > The Validators can be designed as desired. To compare two values, simply > define a validator like CompareValidator(property1, property2, compareRule) > with compareRule = "<", ">",... > > What do you think? > > Thanks. > > Andrej > > _________________________________________________________________ > Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp > > -- > To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> > For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
