Asp.netMVC源码分析--ModelValidation(Server端)实现(1)

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一.MVC Validation 用法:

在Asp.net MVC 框架中如果需要对Model 对象加入验证,我们可以在Model的属性上标记所有继承于ValidationAttribute的Attribute特性.

例如下面的代码中,StringLength/Range/Compare 都是继承于ValidationAttribute类.

 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 中我们可以调用 ValidateModel 方法对Model对象进行验证,如果验证没有通过则会抛出InvalidOperationException异常，同时ModelState.IsValid状态为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);
        }

这里需要注意的是如果我们不调用ValidateModel 方法Action上的Model对象默认也是能够验证的，这是因为在绑定对象阶段DefaultModelBinder.BindComplexElementalModel方法中MVC触发了验证的方法。

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方法源码分析

下面我们看一下MVC 是如何实现ValidateModel方法验证的.

 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         }

我们可以看到第28行MVC是调用了ModelValidator.GetModelValidator 来获取Model 的Validator 对象的.我们看一下这个方法的实现,它返回的是CompositeModelValidator对象.

   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就证明验证没有通过．
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         }

我们再看一下上面第10行，propertyMetadata.GetValidators这个方法的实现,他返回了所有的Validator的实现。并且在12行，调用这些实现的Validate方法进行验证操作.

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

它调用了ModelValidatorProviders.Providers对象的GetValidators 方法. 这个对象的类型是ModelValidatorProviderCollection接下来我们看一下ModelValidatorProviders.Providers的实现

  public static class ModelValidatorProviders {

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

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

    }