Asp.net MVC源碼分析–Model Validation(Server端)實現(1)

一.MVC Validation 用法:

在Asp.net MVC 架構中如果需要對Model 對象加入驗證,我們可以在Model的屬性上標記所有繼承於ValidationAttribute的Attribute特性. 

例如下面的代碼中,StringLength/Range/Compare 都是繼承於ValidationAttribute類.

 public class LogOnModel
    {
        [Required]      
        [StringLength(10)]
public string UserName { get; set; }

        [Required] 
        [Range(5,10)]
public string Password { get; set; }

       [Compare("NewPassword", ErrorMessage = "The new      password and confirmation password do not match.")]
public string ConfirmPassword { get; set; }

        [Display(Name = "Remember me?")]
public bool RememberMe { get; set; }
    }

在Action 中我們可以調用 ValidateModel 方法對Model對象進行驗證,如果驗證沒有通過則會拋出InvalidOperationException異常，同時ModelState.IsValid狀態為false

   [HttpPost]
public ActionResult LogOn(LogOnModel model, string returnUrl)
        {          
this.ValidateModel(model);
if (ModelState.IsValid)
            {
if (MembershipService.ValidateUser(model.UserName, model.Password))
                {
                    FormsService.SignIn(model.UserName, model.RememberMe);
if (Url.IsLocalUrl(returnUrl))
                    {
return Redirect(returnUrl);
                    }
else
                    {
return RedirectToAction("Index", "Home");
                    }
                }
else
                {
                    ModelState.AddModelError("", "The user name or password provided is incorrect.");
                }
            }

// If we got this far, something failed, redisplay form
            return View(model);
        }

這裡需要注意的是如果我們不調用ValidateModel 方法Action上的Model對象預設也是能夠驗證的，這是因為在綁定對象階段DefaultModelBinder.BindComplexElementalModel方法中MVC觸發了驗證的方法。

DefaultModelBinder.cs

 internal void BindComplexElementalModel(ControllerContext controllerContext, ModelBindingContext bindingContext, object model) {
// need to replace the property filter + model object and create an inner binding context
            ModelBindingContext newBindingContext = CreateComplexElementalModelBindingContext(controllerContext, bindingContext, model);

// validation
            if (OnModelUpdating(controllerContext, newBindingContext)) {
                BindProperties(controllerContext, newBindingContext);
                OnModelUpdated(controllerContext, newBindingContext);
            }
        }
protected virtual void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext) {
            Dictionary<string, bool> startedValid = new Dictionary<string, bool>(StringComparer.OrdinalIgnoreCase);

foreach (ModelValidationResult validationResult in ModelValidator.GetModelValidator(bindingContext.ModelMetadata, controllerContext).Validate(null)) {
string subPropertyName = CreateSubPropertyName(bindingContext.ModelName, validationResult.MemberName);

if (!startedValid.ContainsKey(subPropertyName)) {
                    startedValid[subPropertyName] = bindingContext.ModelState.IsValidField(subPropertyName);
                }

if (startedValid[subPropertyName]) {
                    bindingContext.ModelState.AddModelError(subPropertyName, validationResult.Message);
                }
            }
        }

二.ValidateModel方法源碼分析

下面我們看一下MVC 是如何?ValidateModel方法驗證的.

 1  protected internal void ValidateModel(object model) {
 2             ValidateModel(model, null /* prefix */);
 3         }
 4 
 5         protected internal void ValidateModel(object model, string prefix) {
 6             if (!TryValidateModel(model, prefix)) {
 7                 throw new InvalidOperationException(
 8                     String.Format(
 9                         CultureInfo.CurrentCulture,
10                         MvcResources.Controller_Validate_ValidationFailed,
11                         model.GetType().FullName
12                     )
13                 );
14             }
15         }
16 
17  protected internal bool TryValidateModel(object model) {
18             return TryValidateModel(model, null /* prefix */);
19         }
20 
21         protected internal bool TryValidateModel(object model, string prefix) {
22             if (model == null) {
23                 throw new ArgumentNullException("model");
24             }
25 
26             ModelMetadata metadata = ModelMetadataProviders.Current.GetMetadataForType(() => model, model.GetType());
27 
28             foreach (ModelValidationResult validationResult in ModelValidator.GetModelValidator(metadata, ControllerContext).Validate(null)) {
29                 ModelState.AddModelError(DefaultModelBinder.CreateSubPropertyName(prefix, validationResult.MemberName), validationResult.Message);
30             }
31 
32             return ModelState.IsValid;
33         }

我們可以看到第28行MVC是調用了ModelValidator.GetModelValidator 來擷取Model 的Validator 對象的.我們看一下這個方法的實現,它返回的是CompositeModelValidator對象.

   public static ModelValidator GetModelValidator(ModelMetadata metadata, ControllerContext context) {
return new CompositeModelValidator(metadata, context);
        }

CompositeModelValidator.cs 

 1  private class CompositeModelValidator : ModelValidator {
 2             public CompositeModelValidator(ModelMetadata metadata, ControllerContext controllerContext)
 3                 : base(metadata, controllerContext) {
 4             }
 5 
 6             public override IEnumerable<ModelValidationResult> Validate(object container) {
 7                 bool propertiesValid = true;
 8 
 9                 foreach (ModelMetadata propertyMetadata in Metadata.Properties) {
10                     foreach (ModelValidator propertyValidator in propertyMetadata.GetValidators(ControllerContext)) {
11                         //Robbin:一但Validate返回了ModelValidationResult就證明驗證沒有通過．
12                         foreach (ModelValidationResult propertyResult in propertyValidator.Validate(Metadata.Model)) {
13                             propertiesValid = false;
14                             yield return new ModelValidationResult {
15                                 MemberName = DefaultModelBinder.CreateSubPropertyName(propertyMetadata.PropertyName, propertyResult.MemberName),
16                                 Message = propertyResult.Message
17                             };
18                         }
19                     }
20                 }
21 
22                 if (propertiesValid) {
23                     foreach (ModelValidator typeValidator in Metadata.GetValidators(ControllerContext)) {
24                         foreach (ModelValidationResult typeResult in typeValidator.Validate(container)) {
25                             yield return typeResult;
26                         }
27                     }
28                 }
29             }
30         }

我們再看一下上面第10行，propertyMetadata.GetValidators這個方法的實現,他返回了所有的Validator的實現。並且在12行，調用這些實現的Validate方法進行驗證操作.

public virtual IEnumerable<ModelValidator> GetValidators(ControllerContext context) {
return ModelValidatorProviders.Providers.GetValidators(this, context);
        }

它調用了ModelValidatorProviders.Providers對象的GetValidators 方法. 這個對象的類型是ModelValidatorProviderCollection接下來我們看一下ModelValidatorProviders.Providers的實現

  public static class ModelValidatorProviders {

private static readonly ModelValidatorProviderCollection _providers = new ModelValidatorProviderCollection() {
new DataAnnotationsModelValidatorProvider(),
new DataErrorInfoModelValidatorProvider(),
new ClientDataTypeModelValidatorProvider()
        };

public static ModelValidatorProviderCollection Providers {
get {
return _providers;
            }
        }

    }

這個對象初始化時預設包括了三個ValidatorProvider,在這裡我們需要著重注意的是DataAnnotationsModelValidatorProvider,它提供了所有系統預設的Validation規則(除了RemoteAttribute).

下一篇我們來詳細的分析一下DataAnnotationsModelValidatorProvider的實現以及使用的設計模式.

 

轉載請註明出處:http://www.cnblogs.com/RobbinHan/archive/2011/12/15/2289228.html 

本文作者: 十一月的雨 http://www.cnblogs.com/RobbinHan