Asp.net MVC源码分析Model Validation(Server端)实现(1)

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.

 protected internal void ValidateModel(object model) {
            ValidateModel(model, null /* prefix */);
        }

        protected internal void ValidateModel(object model, string prefix) {
            if (!TryValidateModel(model, prefix)) {
                throw new InvalidOperationException(
                    String.Format(
                        CultureInfo.CurrentCulture,
                        MvcResources.Controller_Validate_ValidationFailed,
                        model.GetType().FullName
                    )
                );
            }
        }

 protected internal bool TryValidateModel(object model) {
            return TryValidateModel(model, null /* prefix */);
        }

        protected internal bool TryValidateModel(object model, string prefix) {
            if (model == null) {
                throw new ArgumentNullException("model");
            }

            ModelMetadata metadata = ModelMetadataProviders.Current.GetMetadataForType(() => model, model.GetType());

            foreach (ModelValidationResult validationResult in ModelValidator.GetModelValidator(metadata, ControllerContext).Validate(null)) {
                ModelState.AddModelError(DefaultModelBinder.CreateSubPropertyName(prefix, validationResult.MemberName), validationResult.Message);
            }

            return ModelState.IsValid;
        }

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 

 private class CompositeModelValidator : ModelValidator {
            public CompositeModelValidator(ModelMetadata metadata, ControllerContext controllerContext)
                : base(metadata, controllerContext) {
            }

            public override IEnumerable<ModelValidationResult> Validate(object container) {
                bool propertiesValid = true;

                foreach (ModelMetadata propertyMetadata in Metadata.Properties) {
                    foreach (ModelValidator propertyValidator in propertyMetadata.GetValidators(ControllerContext)) {
                        //Robbin:一但Validate返回了ModelValidationResult就证明验证没有通过．
                        foreach (ModelValidationResult propertyResult in propertyValidator.Validate(Metadata.Model)) {
                            propertiesValid = false;
                            yield return new ModelValidationResult {
                                MemberName = DefaultModelBinder.CreateSubPropertyName(propertyMetadata.PropertyName, propertyResult.MemberName),
                                Message = propertyResult.Message
                            };
                        }
                    }
                }

                if (propertiesValid) {
                    foreach (ModelValidator typeValidator in Metadata.GetValidators(ControllerContext)) {
                        foreach (ModelValidationResult typeResult in typeValidator.Validate(container)) {
                            yield return typeResult;
                        }
                    }
                }
            }
        }

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;
            }
        }

    }

这个对象初始化时默认包括了三个ValidatorProvider,在这里我们需要着重注意的是DataAnnotationsModelValidatorProvider,它提供了所有系统默认的Validation规则(除了RemoteAttribute).

下一篇我们来详细的分析一下DataAnnotationsModelValidatorProvider的实现以及使用的设计模式.

转载请注明出处: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