Asp.net MVC源碼分析–Model Validation(Server端)實現(2)

文章目錄

• 1.AttributeFactories對象
• 2.ValidationAttribte 的 Adapter 設計模式應用
• 3.擷取ModelValidator對象集合
• 4.IValidatableObject介面

前面我們介紹了Model Validation的用法，以及ValidateModel的方法實現,這一篇我們來詳細學習一下DataAnnotationsModelValidatorProvider類的實現。

上一篇:http://www.cnblogs.com/RobbinHan/archive/2011/12/15/2289228.html 

三.DataAnnotationsModelValidatorProvider類詳解1.AttributeFactories對象

首先在這個類中可以看到在初始化時建立了AttributeFactories對象(Dictionary),  這個集合包含了系統內建一些驗證規則。

 1         internal static Dictionary<Type, DataAnnotationsModelValidationFactory> AttributeFactories = new Dictionary<Type, DataAnnotationsModelValidationFactory>() {
 2             {
 3                 typeof(RangeAttribute),
 4                 (metadata, context, attribute) => new RangeAttributeAdapter(metadata, context, (RangeAttribute)attribute)
 5             },
 6             {
 7                 typeof(RegularExpressionAttribute),
 8                 (metadata, context, attribute) => new RegularExpressionAttributeAdapter(metadata, context, (RegularExpressionAttribute)attribute)
 9             },
10             {
11                 typeof(RequiredAttribute),
12                 (metadata, context, attribute) => new RequiredAttributeAdapter(metadata, context, (RequiredAttribute)attribute)
13             },
14             {
15                 typeof(StringLengthAttribute),
16                 (metadata, context, attribute) => new StringLengthAttributeAdapter(metadata, context, (StringLengthAttribute)attribute)
17             },
18         }
19 }

2.ValidationAttribte 的 Adapter 設計模式應用

這裡特別需要注意的是MVC利用了*AttributeAdapter 把 ValidationAttribte 的GetValidationResult方法和 ModelValidator.Validate方法作了一個適配(這裡用到Adapter模式)請看RangeAttributeAdapter/RegularExpressionAttributeAdapter/RequiredAttributeAdapter/StringLengthAttributeAdapter

請參照DataAnnotationsModelValidator.Validate 方法源碼,第7行代碼，就是在這裡進行了適配的工作。

 1  public override IEnumerable<ModelValidationResult> Validate(object container) {
 2             // Per the WCF RIA Services team, instance can never be null (if you have
 3 // no parent, you pass yourself for the "instance" parameter).
 4             ValidationContext context = new ValidationContext(container ?? Metadata.Model, null, null);
 5             context.DisplayName = Metadata.GetDisplayName();
 6 
 7             ValidationResult result = Attribute.GetValidationResult(Metadata.Model, context);
 8             if (result != ValidationResult.Success) {
 9                 yield return new ModelValidationResult {
10                     Message = result.ErrorMessage
11                 };
12             }
13         }

3.擷取ModelValidator對象集合

接下來我們來分析一下DataAnnotationsModelValidatorProvider.GetValidators 方法的實現

 1  protected override IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context, IEnumerable<Attribute> attributes) {
 2             _adaptersLock.EnterReadLock();
 3 
 4             try {
 5                 List<ModelValidator> results = new List<ModelValidator>();
 6 
 7                 // Add an implied [Required] attribute for any non-nullable value type,
 8 // unless they've configured us not to do that.
 9                 if (AddImplicitRequiredAttributeForValueTypes &&
10                         metadata.IsRequired &&
11                         !attributes.Any(a => a is RequiredAttribute)) {
12                     attributes = attributes.Concat(new[] { new RequiredAttribute() });
13                 }
14 
15                 // Produce a validator for each validation attribute we find
16                 foreach (ValidationAttribute attribute in attributes.OfType<ValidationAttribute>()) {
17                     DataAnnotationsModelValidationFactory factory;
18                     if (!AttributeFactories.TryGetValue(attribute.GetType(), out factory)) {
19                         factory = DefaultAttributeFactory;
20                     }
21                     results.Add(factory(metadata, context, attribute));
22                 }
23 
24                 // Produce a validator if the type supports IValidatableObject
25                 if (typeof(IValidatableObject).IsAssignableFrom(metadata.ModelType)) {
26                     DataAnnotationsValidatableObjectAdapterFactory factory;
27                     if (!ValidatableFactories.TryGetValue(metadata.ModelType, out factory)) {
28                         factory = DefaultValidatableFactory;
29                     }
30                     results.Add(factory(metadata, context));
31                 }
32 
33                 return results;
34             }
35             finally {
36                 _adaptersLock.ExitReadLock();
37             }
38         }

我們看到從16-22行, MVC會從屬性的Attributes中找到與AttributeFactories匹配的DataAnnotationsModelValidationFactory, 並調用返回ModelValidator對象，但如果沒有從AttributeFactories找到匹配的對象，則使用DefaultAttributeFactory 委託建立一個ModelValidator對象。

DefaultAttributeFactory內部實現是建立一個DataAnnotationsModelValidator對象在構造時傳入ValidationAttribute， 實際上這個類也是RangeAttributeAdapter等*AttributeAdapter類的基類，它們初始化的邏輯也是一樣的。

1   internal static DataAnnotationsModelValidationFactory DefaultAttributeFactory =
2             (metadata, context, attribute) => new DataAnnotationsModelValidator(metadata, context, attribute);

4.IValidatableObject介面

最後我們看一下DataAnnotationsModelValidatorProvider.GetValidators 方法第25-30行代碼.　

在這個方法中同樣的我們發現MVC利用ValidatableObjectAdapter適配器串連ModelValidator.Validate方法 和 IValidatableObject.Validate介面.

BTW:利用IValidatableObject介面可以實現驗證模型的各個屬性之間的邏輯關係.

 可以參考另一篇文章:http://www.cnblogs.com/bjs007/archive/2011/01/27/1946419.html

總結:

1. Model Validatoin 可以通過在Modol屬性上加入*ValidationAttribute 和 實現IValidatableObject 介面來進行驗證
2. 通過對DataAnnotationsModelValidatorProvider.GetValidators 方法的分析我們得出:
   如果Model中的屬性如果是複雜物件時，即使子物件中標記了*ValidationAttribute也是不會驗證的。

        例如下面的代碼:LogOnModel.ChangePassword　對象中的屬性雖然標記了[Required]但是還是不會驗證的。

 1  public class ChangePasswordModel
 2     {
 3         [Required]
 4         [DataType(DataType.Password)]
 5         [Display(Name = "Current password")]
 6         public string OldPassword { get; set; }
 7 
 8         [Required]
 9         [ValidatePasswordLength]
10         [DataType(DataType.Password)]
11         [Display(Name = "New password")]
12         public string NewPassword { get; set; }
13 
14         [DataType(DataType.Password)]
15         [Display(Name = "Confirm new password")]
16         [Compare("NewPassword", ErrorMessage = "The new password and confirmation password do not match.")]
17         public string ConfirmPassword { get; set; }
18     }
19 
20     public class LogOnModel : IValidatableObject
21     {
22         [Required]       
23         [Display(Name = "User name")]      
24         public string UserName { get; set; }
25         [Required]
26         [Display(Name = "User age")]
27         public string Age { get; set; }
28         [Required]
29         [DataType(DataType.Password)]
30         [Display(Name = "Password")]
31         public string Password { get; set; }       
32         [Display(Name = "Remember me?")]
33         public bool RememberMe { get; set; }
34         [Display(Name = "ChangePassword")]
35         //[Required]
36         public ChangePasswordModel ChangePassword { get; set; }        
37 
38         public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
39         {
40             return Enumerable.Empty<ValidationResult>();
41         }
42     }

疑問 

另外有一點迷惑的是如果,如果把LogOnModel.ChangePassword屬性是標記上[Required],而不從前台傳入這個對象的話，所有LogOnModel屬性上的驗證都會失敗，這一點不知道是不是Asp.net MVC 的bug,如果有人遇到請告訴我。

轉載請註明出處:http://www.cnblogs.com/RobbinHan/archive/2011/12/15/2289403.html

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