asp.net mvc源码分析-ModelValidatorProviders-白红宇

asp.net mvc源码分析-ModelValidatorProviders

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发布时间：2019-06-12

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在上篇文章最后提到了ModelValidatorProviders ，这里我们以DataAnnotationsModelValidatorProvider来说说整过的验证过程。因为 DataAnnotationsModelValidatorProvider这个是我们平时用的最多的情况。其GetValidators的具体实现如下：

protected override IEnumerable
     
       GetValidators(ModelMetadata metadata, ControllerContext context, IEnumerable
      
        attributes) {            _adaptersLock.EnterReadLock();            try {                List
       
         results = new List
        
         ();                // Add an implied [Required] attribute for any non-nullable value type,                // unless they've configured us not to do that.                if (AddImplicitRequiredAttributeForValueTypes &&                        metadata.IsRequired &&                        !attributes.Any(a => a is RequiredAttribute)) {                    attributes = attributes.Concat(new[] { new RequiredAttribute() });                }                // Produce a validator for each validation attribute we find                foreach (ValidationAttribute attribute in attributes.OfType
         
          ()) {                    DataAnnotationsModelValidationFactory factory;                    if (!AttributeFactories.TryGetValue(attribute.GetType(), out factory)) {                        factory = DefaultAttributeFactory;                    }                    results.Add(factory(metadata, context, attribute));                }                // Produce a validator if the type supports IValidatableObject                if (typeof(IValidatableObject).IsAssignableFrom(metadata.ModelType)) {                    DataAnnotationsValidatableObjectAdapterFactory factory;                    if (!ValidatableFactories.TryGetValue(metadata.ModelType, out factory)) {                        factory = DefaultValidatableFactory;                    }                    results.Add(factory(metadata, context));                }                return results;            }            finally {                _adaptersLock.ExitReadLock();            }        }

首先从这里的特性取出是ValidationAttribute特性的attribute，然后根据attribute的type取出相应的DataAnnotationsModelValidationFactory，其中以下4个特性和其DataAnnotationsModelValidationFactory返回的ModelValidator实例一一对应：

RangeAttribute->RangeAttributeAdapter

RegularExpressionAttribute->RegularExpressionAttributeAdapter

RequiredAttribute->RequiredAttributeAdapter

StringLengthAttribute->StringLengthAttributeAdapter

这里的4个AttributeAdapter都继承于 DataAnnotationsModelValidator<TAttribute> -> DataAnnotationsModelValidator ->ModelValidator.

如果没有取消相应的DataAnnotationsModelValidationFactory就调用默认的 DefaultValidatableFactory，它返回一个ValidatableObjectAdapter的一个实例；然后依次调用它们的 Validate方法。以上面4个attribute为例，它们的Validate方法默认的实现在 DataAnnotationsModelValidator中的Validate方法：

public override IEnumerable<ModelValidationResult> Validate(object container) {

// Per the WCF RIA Services team, instance can never be null (if you have

// no parent, you pass yourself for the "instance" parameter).

ValidationContext context = new ValidationContext(container ?? Metadata.Model, null, null);

context.DisplayName = Metadata.GetDisplayName();

ValidationResult result = Attribute.GetValidationResult(Metadata.Model, context);

if (result != ValidationResult.Success) {

yield return new ModelValidationResult {

Message = result.ErrorMessage

};

}

调用每个Attribute的GetValidationResult方法。验证失败就会返回一个ModelValidationResult实例。到这里我们知道DataAnnotationsModelValidator的Validate 方法是怎么调用delete，但是这里类里面还有一个GetClientValidationRules方法，它好像是一个客户端的验证啊。调用 attribute的GetClientValidationRules方法。该方法是在哪里调用的了。我们有时候在view里面有这样的方法 @Html.ValidationMessageFor(model => model.UserName)。

ValidationMessage方法中有这么一段

if (htmlHelper.ViewContext.UnobtrusiveJavaScriptEnabled) {

builder.MergeAttribute("data-valmsg-for", modelName);

builder.MergeAttribute("data-valmsg-replace", replaceValidationMessageContents.ToString().ToLowerInvariant());

}

else {

FieldValidationMetadata fieldMetadata = ApplyFieldValidationMetadata(htmlHelper, modelMetadata, modelName);

// rules will already have been written to the metadata object

fieldMetadata.ReplaceValidationMessageContents = replaceValidationMessageContents; // only replace contents if no explicit message was specified

// client validation always requires an ID

builder.GenerateId(modelName + "_validationMessage");

fieldMetadata.ValidationMessageId = builder.Attributes["id"];