MVC数据验证原理及自定义ModelValidatorProvider实现无编译修改验证规则和错误信息

System.ComponentModel.DataAnnotations

一，简单回顾内置MVC验证的使用

 




二，分析MVC验证的内部过程
1. 实际做验证的是ModelValidator

当我们如上图，在为Person类添加了各种验证规则的dataannotation attributes后，实际操刀来做验证的是[code]DataAnnotationsModelValidator类.

DataAnnotationsModelValidator

namespace System.Web.Mvc
{
public abstract class ModelValidatorProvider
{
public abstract IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context);
}
}

ModelValidatorProvider

三，一个例子，针对ContactInfo的验证

public class ContactInfo
{
public string FirstName { get; set; }
public string LastName{get;set;}
public string Email{get;set;}
public string Url{get;set;}
}

<?xml version="1.0" encoding="utf-8" ?>
<model>
<validator property="FirstName" type="Required"  message="FirstName_Required" />
<validator property="FirstName" type="StringLength" arg-int="50" message="FirstName_Length" />
<validator property="LastName" type="Required"  message="LastName_Required" />
<validator property="LastName" type="StringLength" arg-int="255" message="LastName_Length" />
<validator property="Email" type="Required"  message="Email_Required" />
<validator property="Email" type="StringLength" arg-int="255" message="Email_Length" />
<validator property="Email" type="RegularExpression" arg="^[\w-]+(\.[\w-]+)*@[\w-]+(\.[\w-]+)+$" message="Email_RegularExpression" />
<validator property="Url" type="StringLength" arg-int="255" message="Url_Length" />
<validator property="Url" type="RegularExpression" arg="(http://)?(www\.)?\w+\.(com|net|edu|org)" message="Url_RegularExpression" />
</model>

<?xml version="1.0" encoding="utf-8" ?>
<messages>
<!-- filed error message -->
<message key="FirstName_Required" text="The Frist Name field is required."></message>
<message key="FirstName_Length" text="The field maximum length is 50"></message>
<message key="LastName_Required" text="The Last Name field is required."></message>
<message key="LastName_Length" text="The field maximum length is 255"></message>
<message key="Email_Required" text="The Email field is required."></message>
<message key="Email_Length" text="The field maximum length is 255"></message>
<message key="Email_RegularExpression" text="Invalid email."></message>
<message key="Url_Length" text="The field maximum length is 255"></message>
<message key="Url_RegularExpression" text="Invalid URL."></message>
</messages>

四，具体实现和应用XmlModelValidatorProvider

public class XmlModelValidatorProvider : ModelValidatorProvider
{
// 用来保存System.ComponentModel.DataAnnotations中已经存在的验证规则，也就是MVC自带的Required等验证规则， 因为我们只是验证规则的"源"不一样，一个是代码中，一个是xml，但是验证过程是一样的，所以要重用MVC中的已经写好的验证。
private readonly Dictionary<string, Type> _validatorTypes;

private readonly string _xmlFolderPath = HttpContext.Current.Server.MapPath("~//Content//Validation//Rules");

public XmlModelValidatorProvider()
{
_validatorTypes = Assembly.Load("System.ComponentModel.DataAnnotations").GetTypes()
.Where(t => t.IsSubclassOf(typeof (ValidationAttribute)))
.ToDictionary(t => t.Name, t => t);
}

#region Stolen from DataAnnotationsModelValidatorProvider
// delegate that converts ValidationAttribute into DataAnnotationsModelValidator
internal static DataAnnotationsModelValidationFactory DefaultAttributeFactory =
(metadata, context, attribute) => new DataAnnotationsModelValidator(metadata, context, attribute);

internal static Dictionary<Type, DataAnnotationsModelValidationFactory> AttributeFactories = new Dictionary
<Type, DataAnnotationsModelValidationFactory>
{
{
typeof (RangeAttribute),
( metadata, context, attribute)
=>
new RangeAttributeAdapter (metadata, context, ( RangeAttribute ) attribute)
},
{
typeof (RegularExpressionAttribute),
( metadata, context, attribute)
=>
new RegularExpressionAttributeAdapter (metadata, context, ( RegularExpressionAttribute ) attribute)
},
{
typeof (RequiredAttribute),
( metadata, context, attribute) =>
new RequiredAttributeAdapter (metadata, context, ( RequiredAttribute ) attribute)
},
{
typeof (StringLengthAttribute),
( metadata, context, attribute) =>
new StringLengthAttributeAdapter (metadata, context, ( StringLengthAttribute ) attribute)
}
};

#endregion
// 重写GetValidators方法，该从xml文件中获取。根据xml的配置，返回对应的Validator集合
public override IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context)
{
var results = new List<ModelValidator>();

// whether the validation is for a property or model
// (remember we can apply validation attributes to a property or model and same applies here as well)
var isPropertyValidation = metadata.ContainerType != null && !String.IsNullOrEmpty(metadata.PropertyName);

var rulesPath = String.Format("{0}\\{1}.xml", _xmlFolderPath,
isPropertyValidation ? metadata.ContainerType.Name : metadata.ModelType.Name);

var rules = File.Exists(rulesPath)
? XElement.Load(rulesPath).XPathSelectElements(String.Format(
"./validator[@property='{0}']",
isPropertyValidation ? metadata.PropertyName : metadata.ModelType.Name)).ToList()
: new List<XElement>();

// Produce a validator for each validation attribute we find
foreach (var rule in rules)
{
DataAnnotationsModelValidationFactory factory;

var validatorType = _validatorTypes[String.Concat(rule.Attribute("type").Value, "Attribute")];

if (!AttributeFactories.TryGetValue(validatorType, out factory))
{
factory = DefaultAttributeFactory;
}

var validator = (ValidationAttribute) Activator.CreateInstance(validatorType, GetValidationArgs(rule));
validator.ErrorMessage = rule.Attribute("message") != null &&
!String.IsNullOrEmpty(rule.Attribute("message").Value)
? GetValidationMessage(isPropertyValidation ? metadata.ContainerType.Name : metadata.ModelType.Name, rule.Attribute("message").Value)
: null;
results.Add(factory(metadata, context, validator));
}

return results;
}

private string GetValidationMessage(string model, string key)
{
return MessageProvider.GetViewModelValidationMessage(model, key);
}

// read the arguments passed to the validation attribute and cast it their respective type.
private object[] GetValidationArgs(XElement rule)
{
var validatorArgs = rule.Attributes().Where(a => a.Name.ToString().StartsWith("arg"));
var args = new object[validatorArgs.Count()];
var i = 0;

foreach (var arg in validatorArgs)
{
var argName = arg.Name.ToString();
var argValue = arg.Value;

if (!argName.Contains("-"))
{
args[i] = argValue;
}
else
{
var argType = argName.Split('-')[1];

switch (argType)
{
case "int":
args[i] = int.Parse(argValue);
break;

case "datetime":
args[i] = DateTime.Parse(argValue);
break;

case "char":
args[i] = Char.Parse(argValue);
break;

case "double":
args[i] = Double.Parse(argValue);
break;

case "decimal":
args[i] = Decimal.Parse(argValue);
break;

case "bool":
args[i] = Boolean.Parse(argValue);
break;

default:
args[i] = argValue;
break;
}
}
}

return args;
}
}

ModelValidatorProviders.Providers.Add(new XmlModelValidatorProvider());