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

前两篇我们介绍了ModelValidatoin Server 端的实现,那么我们知道在Web.config 中如果我们把ClientValidationEnabled 设置为true时，那么客户端也可以支持表单验证了. 那么这部份功能是如果实现的呢？今天让我们来一起学习Model validation client 端的实现.

一.ModelClientValidationRule类

这个类定义了如何输出客户端的一些信息:

• ErrorMessage:取得或设定用户端验证规则的错误讯息。
• ValidationParameters:取得验证参数清单。
• ValidationType:取得或设定验证类型。

  public class ModelClientValidationRule {

        private readonly Dictionary<string, object> _validationParameters = new Dictionary<string, object>();
        private string _validationType;

        public string ErrorMessage {
            get;
            set;
        }

        public IDictionary<string, object> ValidationParameters {
            get {
                return _validationParameters;
            }
        }

        public string ValidationType {
            get {
                return _validationType ?? String.Empty;
            }
            set {
                _validationType = value;
            }
        }
}

我们知道了这个类的数据结构,那么这些数据是如何输出的呢?我们看一下RequiredAttributeAdapter类,在这里定义了有一个GetClientValidationRules方法,这个方法返回了ModelClientValidationRequiredRule对象(包含了Required validation 需要输出到客户端的数据).

 public class RequiredAttributeAdapter : DataAnnotationsModelValidator<RequiredAttribute> {
        public RequiredAttributeAdapter(ModelMetadata metadata, ControllerContext context, RequiredAttribute attribute)
            : base(metadata, context, attribute) {
        }

        public override IEnumerable<ModelClientValidationRule> GetClientValidationRules() {
            return new[] { new ModelClientValidationRequiredRule(ErrorMessage) };
        }
    }

二.如果让得到自定义Client Validaton 信息?

上面我们介绍了一些系统内置(Required)的Validation 的输出，那么我们如果需要自定义验证规则如果来输出客户端数据呢？前面我们介绍了DataAnnotationsModelValidatorProvider.GetValidators 方法里自定义的验证是通过DefaultAttributeFactory委托来构造的,让我们顺着这个代码来继续我们的思路。

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

让我接下来看一下DataAnnotationsModelValidator.GetClientValidationRules 方法的实现,我们看到下面代码第4行，说明只有我们自定义的ValidationAtribute只有实现了IClientValidatable接口才能够输出客户端数据。

  public override IEnumerable<ModelClientValidationRule> GetClientValidationRules() {
            IEnumerable<ModelClientValidationRule> results = base.GetClientValidationRules();

            IClientValidatable clientValidatable = Attribute as IClientValidatable;
            if (clientValidatable != null) {
                results = results.Concat(clientValidatable.GetClientValidationRules(Metadata, ControllerContext));
            }

            return results;
        }

三.如果输出自定义Client Validaton 信息到浏览器？

以上的分析是我们得到Cient validation 的数据，那么我们怎么输出这些数据到浏览器呢？　

一般我们在View 页面中的代码都是这样的:

  <div class="editor-label">
               Name
            </div>
            <div class="editor-field">
                @Html.TextBoxFor(m => m.UserName)
                @Html.ValidationMessageFor(m => m.UserName)
</div>

也就是说Client Validaton 信息是通过Html.TextBoxFor方法来输出的，那么我们接下来研究一下这个方法是如何实现的。

在InputExtension.cs 方件的InputHelper方法我们找到了一些与Client Validaton有关的代码片段,下面第9行代码的GetUnobtrusiveValidationAttributes方法就实现了输出。

  // If there are any errors for a named field, we add the css attribute.
            ModelState modelState;
            if (htmlHelper.ViewData.ModelState.TryGetValue(fullName, out modelState)) {
                if (modelState.Errors.Count > 0) {
                    tagBuilder.AddCssClass(HtmlHelper.ValidationInputCssClassName);
                }
            }

            tagBuilder.MergeAttributes(htmlHelper.GetUnobtrusiveValidationAttributes(name, metadata));

GetUnobtrusiveValidationAttributes方法的源码:

 // Only render attributes if unobtrusive client-side validation is enabled, and then only if we've
// never rendered validation for a field with this name in this form. Also, if there's no form context,
// then we can't render the attributes (we'd have no <form> to attach them to).
        public IDictionary<string, object> GetUnobtrusiveValidationAttributes(string name, ModelMetadata metadata) {
            Dictionary<string, object> results = new Dictionary<string, object>();

            // The ordering of these 3 checks (and the early exits) is for performance reasons.
            if (!ViewContext.UnobtrusiveJavaScriptEnabled) {
                return results;
            }

            FormContext formContext = ViewContext.GetFormContextForClientValidation();
            if (formContext == null) {
                return results;
            }

            string fullName = ViewData.TemplateInfo.GetFullHtmlFieldName(name);
            if (formContext.RenderedField(fullName)) {
                return results;
            }

            formContext.RenderedField(fullName, true);

            IEnumerable<ModelClientValidationRule> clientRules = ClientValidationRuleFactory(name, metadata);
            bool renderedRules = false;

            foreach (ModelClientValidationRule rule in clientRules) {
                renderedRules = true;
                string ruleName = "data-val-" + rule.ValidationType;

                ValidateUnobtrusiveValidationRule(rule, results, ruleName);

                results.Add(ruleName, HttpUtility.HtmlEncode(rule.ErrorMessage ?? String.Empty));
                ruleName += "-";

                foreach (var kvp in rule.ValidationParameters) {
                    results.Add(ruleName + kvp.Key, kvp.Value ?? String.Empty);
                }
            }

            if (renderedRules) {
                results.Add("data-val", "true");
            }

            return results;
        }

HtmlHelper 构造函数源码:

  public HtmlHelper(ViewContext viewContext, IViewDataContainer viewDataContainer, RouteCollection routeCollection) {
            if (viewContext == null) {
                throw new ArgumentNullException("viewContext");
            }
            if (viewDataContainer == null) {
                throw new ArgumentNullException("viewDataContainer");
            }
            if (routeCollection == null) {
                throw new ArgumentNullException("routeCollection");
            }

            ViewContext = viewContext;
            ViewDataContainer = viewDataContainer;
            RouteCollection = routeCollection;
            ClientValidationRuleFactory = (name, metadata) => ModelValidatorProviders.Providers.GetValidators(metadata ?? ModelMetadata.FromStringExpression(name, ViewData), ViewContext).SelectMany(v => v.GetClientValidationRules());
        }

最终我们看到在GetUnobtrusiveValidationAttributes方法内部，MVC 调用了ClientValidationRuleFactory委托来得到clientRules对象它的类型是IEnumerable<ModelClientValidationRule>,这样我们在Model上标记的Client Validation数据就输出到了浏览器端。

--------------------------------------风搔分割线-------------------------------------------------

那么通过以上这些分析我们知道了Server 端如何输出Client Validation数据，那么JavaScript是怎么来进行验证的呢？　

下一篇我们来分析jquery.validate.unobtrusive.js　的源码，这里面实现了MVC的客户端验证逻辑。

　

转载请注明出处:http://www.cnblogs.com/RobbinHan/archive/2011/12/19/2293121.html

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