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。

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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。

　

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