With my understading, the nature of a Action is that properties can be pushed w/ request parameter values. And, one wonderful feature is that Struts2 allows you to directly populate parameter values against Class type property ;)
Assuming there exists a Action and property class as below,
class Action extends ActionSupport {
User user;
#Action(value="hello" {#result=(.......)})
public void execute() {
........
}
.....
public void setUser(User user) {
this.user = user;
}
public User getUser() {
return this.user;
}
}
class User {
String name;
.....
public void setName(String name) {
this.name = name;
}
public String getName() {
return this.name;
}
}
you could populate User class property by doing like this.
http://...../hello.action?user.name=John or via jsp page
Then, I realize that there are actually people make an Action property as a Interface type. My question is what is the reason behind this. If there is a sample code demonstrating it will be great.
Thanks in advance!
Sorry, but your question does not make much sense.
To clarify:
"Properties": in Java a "property" of a class is something that is accesible via getter/setters method (setXXX() / getXXX() => property XXX), tipically (but not necessarily) corresponds to a private field.
In Struts2 you have an Action object and typically (not necessarily, not always) the properties are populated (set) from the request (via the "Parameters" interceptor), and later in the view stage read from the JSP (or whatever) page.
So, in your example, for the request http://...../hello.action?user.name=John , Struts2 would try to find in your action (...actually in your value stack) a property "user" which has a property "name", and try to set it (if the types are convertible). That is, he would try to call something like yourAction.getUser().setName("John") . Struts2 does not know -does not care- what type are the properties "User" or "Name", even if they are real fields or not. (They are expected to behaviour as "beans", though: i.e. they should have a default constructor).
Why and when you should code interfaces instead of concrete classes is something that is explained in any Java book, it's just a standard good practice and there are tons of pages about it. It has nothing to do with Struts2. In this context, for an Action, one is tipically only interested in doing so for some "service" fields, objects that are typically long-lived (perhaps singletons), are not instantiated by the action itself (nor by the request!). So, those interfaces are NOT the properties we are considering here, they ( usually ) are not exposed publically and usually are not populated nor read from the client.
Related
My Post call does not return the correct Model type. It always use the baseObject instead of the correct derived object that I passed in from the Get
RestaurantViewModel.cs
public class RestaurantViewModel{
public Food BaseFoodObject{get;set;}
}
Food.cs
public class Food{
public string Price{get;set;)
}
Bread.cs -- Inherit from Food
public class Bread:Food{
public int Unit{get;set;}
}
Milk.cs -- Inherit from Food
public class Milk:Food{
public string Brand{get;set}
}
Editor For Template for Bread. Display the unit and allow user to edit
Index.html
#Model RestaurantViewModel
#using(Html.BeginForm("SaveFood", "Food"))
{
#Html.EditorFor(m=>m.BaseFoodObject)
<input type="submit" value="Process"/>
}
Bread.cshtml
#Model Bread
<div>
#Html.TextboxFor(bread=>bread.Unit)
</div>
FoodController.cs
public ActionResult Index(){
Bread bread = new Bread(){
Price = "$10",
Unit = 1
}
RestaurantViewModel viewModel = new RestaurantViewModel(){
BaseFoodObject = bread
}
return View(viewModel);
}
public ActionResult Post(RestaurantViewModel viewModelPost)
{
// When I inspect the viewModelPost, there is no attribute for unit
}
Final Result:
1. The display looks correct. EditorFor is smart enough to pick the correct editor template and display the value correctly
2. The Save does not work. The Unit attribute of Bread Object does not get passed in with the RestaurantViewModel. The reason for that is the RestaurantViewModel used the Food object instead of Bread
I hope there is away to modify the EditorFor and tell it to use the Model in the View or the Object Type that I passed in when I display it.
Thanks
Update 1: I solved this problem by using the custom binder and using a factory to decide which object I really want. This helps construct the correct Model which I want
MVC is stateless. A couple of references.
There's a couple of statements in your question that conflict with this, and how MVC binding works eg:
My Post call does not return the correct Model type.
Possibly just terminology, but your Post call does not 'return a model type' - it goes into the model that's defined in the post action, in this case RestaurantViewModel.
instead of the correct derived object that I passed in from the Get
because it is stateless, it knows nothing about the model you passed in from the get... absolutely nothing.
The final html rendered via the getaction+view.cshtml+model is not linked to the postaction. You could just as easily take the rendered html, save it, reboot your PC, reload the rendered html and it will work exactly the same way.
a way to modify the EditorFor and tell it to use the Model in the View or the Object Type that I passed in when I display it
When you use EditorFor it sets an ID and name attribute based on the model it was bound to, so it already does this, but perhaps you are not binding to the model you want to bind to to get the correct id.
So, to the question, if, in 'normal' C# code you were to instantiate a new instance of RestaurantViewModel, what would you expect the type of BaseFoodObject to be?
This is what the ModelBinder is doing - it's creating a new RestaurantViewModel.
As your post action method's signature does not include anything to do with Bread - all the bread properties are ignored.
Some options:
Check for the food properties after binding and read them manually (probably the quickest+easiest but not very "mvc-ish")
public ActionResult Post(RestaurantViewModel viewModelPost)
{
if (!string.IsNullOrEmpty(Request.Form["Unit"]))
// it's a bread form
to make this easier, you could provide a hidden field with the type
if (Request.Form["Type"] == typeof(Bread).Name)
{
var bread = new Bread { Unit = Request.Form["Unit"] }
Add bread to the action so it's bound
public ActionResult Post(RestaurantViewModel viewModelPost, Bread bread)
but then, obviously, it won't work for milk.
So could extend this using an ActionNameSelector to select the correct action
public ActionResult PostBread(RestaurantViewModel viewModelPost, Bread bread)
public ActionResult PostMilk(RestaurantViewModel viewModelPost, Milk milk)
[AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
public sealed class FoodSelectorAttribute : ActionNameSelectorAttribute
{
public override bool IsValidName(ControllerContext controllerContext, string actionName, MethodInfo methodInfo)
{
... check if provided parameters contains bread/milk
(related link but not a solution to this specific case)
Another option might be to change the Restaurant type to a generic, but would require a few more changes (and ideally use of interfaces), and more details (provided here as an idea, rather than a solution)
The basics would be:
public class RestaurantViewModel<T>
where T: Food
{
}
public ActionResult Post(RestaurantViewModel<Bread> viewModelPost)
public ActionResult Post(RestaurantViewModel<Milk> viewModelPost)
but I've not confirmed if the default ModelBinder would work in this case.
The problem comes with the post. Once you post, all you have is a set of posted data and a parameter of type, RestaurantViewModel. The modelbinder sets all the appropriate fields on Food because that's all it knows. Everything else is discarded. There's nothing that can be done about this. If you need to post fields related to Bread then the type of your property must be Bread. That's the only way it will work.
I've created FacesComponent which I want to initialize in constructor/postconstructor. The problem is that getAttributes() is empty in there. Below is the example.
#FacesComponent("articleComponent")
public class ArticleFacesComponent extends UINamingContainer {
private Article article;
public ArticleFacesComponent() {
Object idObj = getAttributes().get("articleId"); // I want to get article id to initialize object but getAttributes() is empty
...
article = em.find(Article.class, id);
}
}
You need to perform the job in the encodeAll() method. It's invoked during render response, when the component is about to be rendered.
#Override
public void encodeAll(FacesContext context) throws IOException {
// Here.
super.encodeAll(context);
}
Given that you're extending from UINamingContainer, you're most likely creating a backing component for a composite component. In that case, this article should provide you useful insights to get started: composite component with multiple input fields.
Unrelated to the concrete problem, accessing the DB in a component is a smell. Rather pass a fullworthy Article instance as component value instead of its ID. The component/renderer should only deal with front-end (HTTP/HTML) stuff based on the model, not with back-end (DB/SQL) stuff. You should provide the component exactly the model it needs to work with.
Like #BalusC said. But if you are using PrimeFaces you have to overwrite the encodeBegin() method. Else you may overwrite encodeAll().
I have a search form that can search in different provider.
I started out by having a base controller
public SearchController : Controller
{
protected readonly ISearchService _searchService
public SearchController(ISearchService searchService)
{
_searchService= searchService;
}
public ActionResult Search(...)
{
// Use searchService to query and return a view.
}
}
And child controllers
TwitterController : SearchController
{
...
}
NewsController : SearchController
{
...
}
I use StructureMap to insert all my dependencies in the controller. With this setup, I was able to change the SearchService depending on the type of the controller being instanciated.
x.For<ISearchService>().ConditionallyUse(o =>
{
o.TheDefault.Is.OfConcreteType<NewsSearchService>();
o.If(c => c.ParentType == typeof(TwitterController))
.ThenIt.Is.OfConcreteType<TwitterSearchService>();
...
});
That even allowed me to set different Views for each controller, (just putting the corresponding folder (Twitter, News...) and the Parent controller is still handling all the Search, with a simple
return View(results)
which is displaying the correct view specific to twitter, news, or other
Now that was cool and looked great, I a single form and the different views are displayed in tabs on the same page. That's where it starts to get complicated with this approach. The form has to post to /Twitter to search in twitter, to /News to search in news... which means I should change the action parameter of the form depending on which tab I am and display the correct tab on when the form returns depending on.. the url? craziness follows.
If you have built something like this already or know what's the best approach to this, please advices are welcome.
Now I think I would have less pain using a parameter in the form and posting to a single controller. I am thinking of injecting the correct SearchService depending on this parameter. What would be the best approach? I thought of using a model binder,
So I would have my ActionMethod that look like this:
public ActionResult Search(ISearchService service, Query query)
{
var results = service.Find(query);
}
But I think would need to make a call like this in the ModelBinder
ObjectFactory.GetInstance(...);
Based on the querystring parameter that describe which provider to use, and that doesn't seem more elegant to me. I feel stuck, help :(.
Whenever you need to vary a dependency based on a run-time value, Abstract Factory is the general solution.
Instead of injecting ISearchService into your Controllers, inject an ISearchServiceFactory:
public SearchController : Controller
{
private readonly ISearchServiceFactory searchServiceFactory;
public SearchController(ISearchServiceFactory searchServiceFactory)
{
if (searchServiceFactory == null)
{
throw new ArgumentNullException("searchServiceFactory");
}
this.searchServiceFactory = searchServiceFactory;
}
public ActionResult Search(...)
{
// Use searchServiceFactory to create an ISearchService based on
// run-time values, and use it to query and return a view.
}
}
It is not entirely clear to me which run-time value you need to vary on, but assuming that it's the Query, ISearchServiceFactory might be defined like this:
public interface ISearchServiceFactory
{
ISearchService Create(Query query);
}
I was trying to figure out how to use the abstract factory pattern and still let structuremap resolve all the dependencies of my components.
I believe that is the way I am going to implement it, but I submit this here to get some feedback if someone would read this.
As explain in the previous answer, I do not want to build the whole object graph depending on which provider I need in the Abstract factory.
ie :
class StatServiceFactory : IStatServiceFactory
{
public IStatService Create(string provider)
{
switch(provider)
{
case "blog":
return new StatService(IFacetRepository,ISearchManager,IConfigManager,BooleanQueryBuilder);
//How to resolve the Config, the SearchManager, and BooleanQueryBuilder?
//Add more abstract factories? It starts to get messy in my opinion...
}
}
}
What I can do is have the abstract factory use my container to create an instance of my search managers depending on a parameter (coming from the querystring in my case)
Structuremap allows to create named instances this way :
x.For<ISearchManager>().Use<AbcSearchManager>().Named("Abc");
x.For<ISearchManager>().Use<DefSearchManager>().Named("Def");
I need a way to inject the container in my Abstract factory.
I would probably wrap the container in a wrapper defined like this. That would keep me from leaking Structuremap into my project. I dont need more that those 2 features within the abstract factory anyway, but it is not necessary:
public interface IContainerWrapper
{
object GetInstance<T>();
object GetNamedInstance<T>(string key);
}
and the implementation :
public class ContainerImpl : IContainerWrapper
{
private readonly Container _container
public ContainerImpl(Container container)
{
_container = container;
}
...
}
And setup StructureMap to resolve dependencies to my abstract factory like that :
x.For<IContainer>.Use(new ContainerImpl(this));
x.For<IFactory>.Use<Factory>()
My factory would be then much simpler and would create my instance like that :
public class SearchmanagerFactory
{
private readonly IContainerWrapper _container;
public SearchmanagerFactory(IContainerProvider containerProvider)
{
_container = containerProvider;
}
public ISearchManager Create(string provider)
{
//eed to handle the bad input for provider.
return (ISearchManager)
_container.Resolve<ISearchManager>(provider);
}
}
That seems pretty clean this way :).
Thoughts?
This is more an extensive comment than an answer to explain why an AbstractFactory seems complicated. Here is something that looks closer from the reality:
class StatServiceFactory : IStatServiceFactory
{
public IStatService Create(string provider)
{
switch(provider)
{
case "blog":
return new StatService(IFacetRepository,ISearchManager,IConfigManager,BooleanQueryBuilder);
//How to resolve the Config, the SearchManager, and BooleanQueryBuilder?
//Add more abstract factories? It starts to get messy in my opinion...
}
}
}
The FacetRepository is the same for any provider, but the SearchManager changes, the ConfigManager changes, and the BooleanQueryBuilder is an abstract class with different implementation for different provider (because every API doesnt use the same keyword for their queries) All those dependencies are currently resolved by structuremap, based on the type of the controller.
I would really like to keep the benefit of StructureMap here, rather than using factories all the way, for each different pieces.'
Please see my edit at the end of my question for another suggestion to my problem.
I refactored some common properties into a base class and immediately my model updates started failing. UpdateModel() and TryUpdateModel() did not seem to update inherited public properties.
I cannot find detailed info on MSDN nor Google as to the rules or semantics of these methods. The docs are terse (http://msdn.microsoft.com/en-us/library/dd470933.aspx), simply stating:
Updates the specified model instance using values from the controller's current value provider.
SOLVED: MVC.NET does indeed handle inherited properties just fine. This turned out to have nothing to do with inheritance. My base class was implemented with public fields, not properties. Switching them to formal properties (adding {get; set; }) was all I needed. This has bitten me before, I keep wanting to use simple, public fields. I would argue that fields and properties are syntactically identical, and could be argued to be semantically equivalent, for the user of the class.
MVC will bind to properties of the inherited class. The model binder calls something like typeof(yourtype).GetProperties() which returns all the inherited members just fine.
Just tested it out with:
public class PersonBase
{
public string Name { get; set; }
}
public class User : PersonBase
{
public string FavoriteFood { get; set; }
}
"My assumption is the methods are reflecting on the top class only,"
How would that work? The "top" class IS the base class too.
this one made me curious too.
i made a edit form for a class Manager who derives from a Person
(after all, managers are persons too :-))
then in this action method
public ActionResult Edit(Manager manager )
{
return View(manager);
}
which wass called from a view with the Manager (derived type) as strong typed Model variable, when hovering the manager variable, it shows me the base class (it actually said: base: Person ) AND the one extra property for the manager
tried the formcollection too, and that also works:
public ActionResult Edit(FormCollection formCollection )
{
Manager manager = new Manager();
UpdateModel(manager );
return View(manager);
}
Related: What’s the best way to implement field validation using ASP.NET MVC?
Let's suppose a solution with the following projects:
Foo; // the MVC web project
Foo.Models;
Foo.Repositories;
Foo.Services;
Foo.Models is the domain of the application with all the entities, doesn't matter if using EF, NH, POCO or whatever. Here's an example:
public class User
{
public string Username { get; set; }
public string Email { get; set; }
public string Password { get; set; }
}
In Foo.Repositories there is a UserRepository and in Foo.Services there is a UserService.
In the web application let's consider a model binder like following:
public class UserBinder : DefaultModelBinder
{
//...
}
I see three different options on where to put the validation:
In Foo.Models like the following:
public class User
{
public string Username { get; set; }
public string Email { get; set; }
public string Password { get; set; }
public ICollection<KeyValuePair<string, string>> ValidateErrors()
{
//Validate if Username, Email and Password has been passed
}
}
In Foo.Services like:
public class UserService
{
public ICollection<KeyValuePair<string, string>> ValidateErrors()
{
//Validate if Username, Email and Password has been passed
}
}
In Foo inside the model binder:
public class UserBinder : DefaultModelBinder
{
protected override void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var user = (User)bindingContext.Model;
// validate everything here
base.OnModelUpdated(controllerContext, bindingContext);
}
}
Another thing to notice is that considering the first 2 options [Model and Service] there is another decision to make: ValidateErrors method can be called directly on the controller or inside the Binder.
I have 2 questions on the scenario:
Should the validation be:
In the Model being called from the controller?
In the Model being called from the binder?
In the Service being called from the controller?
In the Service being called from the binder?
Directly in the Binder?
Any other idea?
All the above scenario discuss about the User creation. But what about User logon?
Let's say user uses the username and password to login in the application, so it won't need to validate the e-mail.
Where this validation should be?
In the Model being called from the controller?
In the Service being called from the controller?
Any other idea?
Check out the ASP.NET MVC Contact Manager Sample Application it has a very good architecture im my opinion
http://www.asp.net/learn/mvc/tutorial-26-cs.aspx'>http://www.asp.net/learn/mvc/tutorial-26-cs.aspx
I'm a big fan of putting calling the validation from the controllers and having the validation routine return an ActionResult so the controller can know what to do with the result.
For what it's worth, here's what I have scrounged up in my current project:
I have Models, Repositories (you can call them Services if you like), and ViewModels. I try to avoid writing custom model binders because (a) it's boring and (b) a strange place to put validation, IMHO. To me, a model binder is just taking items from the request and shoving them into an object. PHP, for example, doesn't do any validation when plucking items from a header into the $_POST array; it's the thing we plug the array into that cares about its contents.
My Model objects generally never allow themselves to enter an invalid state. This means that required parameters are passed in during constructors and properties will throw exceptions if they're attempted to be set with invalid values. And, in general, I try to design my Model objects to be immutable. For example, I have an Address object for mailing addresses that is constructed with an AddressBuilder object with looks at the field requirements for a given country by inspecting an AddressScheme that can be retrieved from the AddressSchemeRepository. Phew. But I think it's a good example because it takes something conceptually simple ("validate a mailing address") and makes it complicated in real world usage ("we accept addresses from over 30 countries, and those formatting rules are sitting in a database, not in my code").
Since constructing this Model object is kind of a pain--as well it should be, since it's being quite particular about the data that gets loaded into it--I have a, say, InputAddressViewModel object that my view binds to. The InputAddressViewModel implements IDataErrorInfo so that I get ASP.NET MVC's DefaultModelBinder to add errors to the ModelState automatically. For simple validation routines that I know ahead of time (phone number formatting, first name required, e-mail address format), I can implement these right in the InputAddressViewModel.
The other advantage of having a view model is that because it is shamelessly tailored to a particular view, your real model is more reusable because it doesn't have to make any weird concessions to make it suitable for UI display (e.g., needs to implement INotifyPropertyChanged or Serializable or any of that mess).
Other validation errors about the address I won't know about until I interact with my AddressScheme in my actual Model. Those errors will be there controller's job of orchestrating into the ModelState. Something like:
public ActionResult InputAddress(InputAddressViewModel model)
{
if (ModelState.IsValid)
{
// "Front-line" validation passed; let's execute the save operation
// in the our view model
var result = model.Execute();
// The view model returns a status code to help the
// controller decide where to redirect the user next
switch (result.Status)
{
case InputAddressViewModelExecuteResult.Saved:
return RedirectToAction("my-work-is-done-here");
case InputAddressViewModelExecuteResult.UserCorrectableError:
// Something went wrong after we interacted with the
// datastore, like a bogus Canadian postal code or
// something. Our view model will have updated the
// Error property, but we need to call TryUpdateModel()
// to get these new errors to get added to
// the ModelState, since they were just added and the
// model binder ran before this method even got called.
TryUpdateModel(model);
break;
}
// Redisplay the input form to the user, using that nifty
// Html.ValidationMessage to convey model state errors
return View(model);
}
}
The switch may seem repulsive, but I think it makes sense: the view model is just a plain old class and doesn't have any knowledge of the Request or the HttpContext. This makes the logic of the view model easy to test in isolation without resorting to mocking and leaves the controller code left to, well, control by interpreting the model's result in a manner that makes sense on a Web site--it could redirect, it could set cookies, etc.
And the InputAddressViewModel's Execute() methods looks something like (some people would insist on putting this code into a Service object that the controller would call, but to me the view model will do so much finagling of the data to make it fit the real model that it makes sense to put it here):
public InputAddressViewModelExecuteResult Execute()
{
InputAddressViewModelExecuteResult result;
if (this.errors.Count > 0)
{
throw new InvalidOperationException(
"Don't call me when I have errors");
}
// This is just my abstraction for clearly demarcating when
// I have an open connection to a highly contentious resource,
// like a database connection or a network share
using (ConnectionScope cs = new ConnectionScope())
{
var scheme = new AddressSchemeRepository().Load(this.Country);
var builder = new AddressBuilder(scheme)
.WithCityAs(this.City)
.WithStateOrProvinceAs(this.StateOrProvince);
if (!builder.CanBuild())
{
this.errors.Add("Blah", builder.Error);
result = new InputAddressViewModelExecuteResult()
{
Status = InputAddressViewModelExecuteStatus
.UserCorrectableError
};
}
else
{
var address = builder.Build();
// save the address or something...
result = new InputAddressViewModelExecuteResult()
{
Status = InputAddressViewModelExecuteStatus.Success,
Address = address
};
}
}
return result;
}
Does this make sense? Is it a best practice? I have no idea; it's certainly verbose; it's what I just came up with in the past two weeks after thinking about this problem. I think you're going to have some duplication of validation--your UI can't be a complete imbecile and not know what fields are required or not before submitting them to your model/repositories/services/whatever--otherwise the form could simply generate itself.
I should add that the impetus for this is that I've always kind of detested the Microsoft mentality of "set one property -> validate one property" because nothing ever works like that in reality. And you always end up getting an invalid object persisted because someone forgot to call IsValid or some such on the way to the data store. So another reason for having a view model is that it tailors itself to this concession so we get a lot of CRUD work of pulling items from the request, validation errors in the model state, etc quite easily without having to compromise the integrity of our model itself. If I have an Address object in hand, I know it's good. If I have an InputAddressViewModel object in hand, I know I need to call it's Execute() method to get that golden Address object.
I'll look forward to reading some of the other answers.
After a lot of research I think I got the answers to my question so i decided to share.
The validation code should be on Model.
As per the idea of "thin controller, fat model" AND considering that a model would know what it needs to validate or not.
For example, let's say I decide to user the Foo.Models in other solution but I decide NOT to use any other project and the validation is in other project.
I'll have to re-code the entire validation in this case what is a total waste of time, right?
OK. The validation code must be in the model but where should it be called?
This validation must be called where you're saving it to your database or file.
As in the proposed scenario I'm considering the repository as a domain, then we should consider putting the validation just before the change saving [in this example I'm using Entity Framework but it's not necessary, it's just to show]:
public class UserRepository : IRepository<User>
{
public void Create(User user)
{
user.Validate();
var db = dbFooEntities();
db.AddToUsers(user);
db.SaveChanges();
}
}
As per MS recommendation, the model validation should raise an exception and the controller must populate the ModelState with the errors found [I'll try to update this answer with a sample code on that as soon as I finish my app].
With that we have an answer for question #1.
What about question #2, regarding the login validation?
As login is not a situation where you're persisting your data, the validation should stay on the Service since logging in is a service in this case.
So, the answers for the question are:
In the Model being called from the REPOSITORY [that is called by the controller]
In the Service being called from the controller
This is very interesting and it helps me a lot in deciding where to put validation.
currently I feel the most for each model implementing a "Validate" method, which is called from a Repository or a Service.
However, what about validating if a chosen username is unique?
Should that code be inside the User model, or inside the UserService class, or in the UserRepository class?
If the uniqueness validation should be inside the User model, then the User model should have access to either the UserService or the UserRepository class. Is that OK, or is that against any "best practice" pattern?
For example:
class User
{
string Username { get; set; }
string Email { get; set; }
string Password { get; set; } // hashed and salted of course :)
IEnumerable<RuleViolation> Validate()
{
List<RuleViolation> violations = new List<RuleViolation>();
IUserService service = MyApplicationService.UserService; // MyApplicationService is a singleton class, especialy designed so that the User model can access application services
// Username is required
if ( string.IsNullOrEmpty(Username) )
violations.Add(new RuleViolation("Username", "Username is required"));
// Username must be unique: Should uniqueness be validated here?
else if( !service.IsUsernameAvailable(Username)
violations.Add(new RuleViolation("Username", "Username is already taken!"));
// Validate email etc...
return violations;
}
}
interface IUserRepository
{
void Save(User item);
}
interface IUserService
{
IUserRepository UserRepository { get; }
void Save(User item);
}
class UserService : IUserService
{
public UserService(IUserRepository userRepository)
{
this.UserRepository = userRepository;
}
IUserRepository UserRepository { get; private set}
public void Save(User user)
{
IEnumerable<RuleViolation> violations = user.Validate();
if(violations.Count() > 0)
throw new RuleViolationException(violations); // this will be catched by the Controller, which will copy the violations to the ModelState errors collection. But the question is, should we validat the user here, or in the UserRepository class?
UserRepository.Save(user);
}
}
class UserRepository : IUserRepository
{
void Save(User item)
{
IEnumerable<RuleViolation> violations = user.Validate();
if(violations.Count() > 0)
throw new RuleViolationException(violations); // this will be catched by the Controller, which will copy the violations to the ModelState errors collection. But the question is, should we validate the user here, or in the UserService class?
UserRepository.Save(user);
}
}
My guess would be that validation should be as close to the model as possible. So I'd say that the UserRepository should be the one responsible for validating it's model being added.
The most important queston for me is: Should the User model know about the IUserService / IUserRepository interfaces so that it can validate the Username uniqueness?
Or should the IUserService service validate uniqueness?
I'm curious about your views on this!
I'm using the DataAnnotations attributes in combination with a MVC model binder to do my validation and its pretty awesome. Since I treat User input as Command View Models its the cleanest way to keep domain clean from outside concerns.
http://bradwilson.typepad.com/blog/2009/04/dataannotations-and-aspnet-mvc.html
This also allows me to take advantage of AutoForm by LosTechies.com:
http://www.lostechies.com/blogs/hex/archive/2009/06/17/opinionated-input-builders-part-8-the-auto-form.aspx
And I expect the client side validation tools in MVC 2, VS 2010 to take advantage of these attributes as well.
So I'm whipping out user input view models, commands, at a furious pace right now and tying them into not only the AutoForm functionality but my own custom UI templates to get AutoGrid and AutoOutput from these attributes as well.
Nothing is better than saying:
Html.AutoForm(Model);
Or
Html.AutoGrid(Model.Products);
And getting validation and html generation in a very DRY and orthogonal way. My controllers are light, my domain pristine, and my time is unoccupied by writing the same if( string.IsNullOrEmpty() ) method on every object with a FirstName property.
For me the approach was not as "philosophical" as others have written about. I'm trying to be very pragmatic about MVC development and I get a ton of bang for the buck out of these bits.