MVC<2:路由映射原理（写在最后）>

MVC路由机制 （原文请点击http://blog.csdn.net/xiaoyong322/article/details/7401391）

目录(?)[-]

序

MVC 学习索引点击即可

一个请求进入IIS后

传统ASPNET 路由部分

MVC 路由部分　

MVC 学习索引(点击即可)

一个请求进入IIS后

传统ASP.NET 路由部分

1、IIS根据文件类型将请求转交给相应的处理程序，如果属于ASP.NET文件，则将请求转发给aspnet_isapi.dll。(注：在II6和IIS7上的处理方式是有区别的)

2、 HTTP处理模块UrlRoutingModule接收到请求后，循环调用其RouteCollection集合中的RouteBase对象，找出匹配的RouteBase。

3、根据匹配的RouteBase对象返回的RoueData对象，获取RouteHandler。

4、RouteHandler返回一个HTTP处理程序(IHttpHandler)，最终通过此处理程序处理请求，生成应答内容。

5.、如果RouteHandler为MvcRouteHandler，并且其返回的HTTP处理程序为MvcHandler，则进入到MVC框架，MvcHandler对象负责调用适当的控制器和活动方法，生成应答内容。

MVC 路由部分　

关键类说明

１、UrlRoutingModule类

此类事路由系统的核心类，其主要功能是根据请求上下文找出合适的RouteBase对象。属性RouteCollection是一个RouteBase对象集合，UrlRoutingModule接收到请求后，循环RouteCollection集合中的RouteBase对象，调用其GetRouteData方法，如果该方法返回的RouteData对象不为null，则终止循环，将RouteData对象存入RequestContext。然后根据RouteData的RouteHandler获取合适的IHttpHandler处理程序。

UrlRoutingModule实际上是一个ASP.NET的HTTP 处理模块，所以它通过配置文件的<httpMoudles>配置节点来添加的。

2、RouteTable类

用于存储应用程序的路由集合，静态属性Routes返回应用程序的路由集合，它实际等同于UrlRoutingModule的RouteCollection属性。通过RouteTable.Routes.Add方法可以添加自定义的RouteBase对象。

3、RouteBase类

表示一个ASP.NET路由的基类[System.Web.Routing]，所有的路由都应该继承自此类。



GetRouteData方法检查传入的HttpContextBase信息是否符合路由规则，符合则返回一个RouteData对象，不符合则返回null，此方法由UrlRoutingModule类在循环RouteTable.Routes集合时调用。

GetVirtualPath方法根据路由数据生成相应的Url。

4、Route类

是RouteBase的一个实现，主要添加了几个属性：

Constraints： 对URL的约束条件

DataTokens：传递到路由处理程序的自定义值

Defaults：Url不包含指定参数时得默认值

RouteHandler：一个路由处理程序(IRouteHandler)


5、IRouteHandler接口

路由处理程序接口，包含一个GetHttpHandler方法，用于返回一个IHttpHandler处理程序对象。

6、MvcRouteHandler类

Mvc框架实现的一个路由处理程序，其GetHttpHandler方法返回一个MvcHandler对象

[csharp] view plaincopyprint?

#region IRouteHandler Members

IHttpHandler IRouteHandler.GetHttpHandler(RequestContext requestContext) {

return GetHttpHandler(requestContext);

}

#endregion

#region IRouteHandler Members
IHttpHandler IRouteHandler.GetHttpHandler(RequestContext requestContext) {
return GetHttpHandler(requestContext);
}
#endregion

7、MvcHandler

由MvcRouteHandler返回，根据请求信息，调用合适的控制器和方法，生成应答内容。

[csharp] view plaincopyprint?

publicclass MvcHandler : IHttpAsyncHandler, IHttpHandler, IRequiresSessionState {

privatestaticreadonlyobject _processRequestTag = newobject();

private ControllerBuilder _controllerBuilder;

internalstaticreadonlystring MvcVersion = GetMvcVersionString();

publicstaticreadonlystring MvcVersionHeaderName = "X-AspNetMvc-Version";

public MvcHandler(RequestContext requestContext) {

if (requestContext == null) {

thrownew ArgumentNullException("requestContext");

}

RequestContext = requestContext;

}

internal ControllerBuilder ControllerBuilder {

get {

if (_controllerBuilder == null) {

_controllerBuilder = ControllerBuilder.Current;

}

return _controllerBuilder;

}

set {

_controllerBuilder = value;

}

}

publicstaticbool DisableMvcResponseHeader {

get;

set;

}

protectedvirtualbool IsReusable {

get {

returnfalse;

}

}

public RequestContext RequestContext {

get;

privateset;

}

protectedinternalvirtualvoid AddVersionHeader(HttpContextBase httpContext) {

if (!DisableMvcResponseHeader) {

httpContext.Response.AppendHeader(MvcVersionHeaderName, MvcVersion);

}

}

protectedvirtual IAsyncResult BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, object state) {

HttpContextBase iHttpContext = new HttpContextWrapper(httpContext);

return BeginProcessRequest(iHttpContext, callback, state);

}

protectedinternalvirtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state) {

return SecurityUtil.ProcessInApplicationTrust(() => {

IController controller;

IControllerFactory factory;

ProcessRequestInit(httpContext, out controller, out factory);

IAsyncController asyncController = controller as IAsyncController;

if (asyncController != null) {

// asynchronous controller

BeginInvokeDelegate beginDelegate = delegate(AsyncCallback asyncCallback, object asyncState) {

try {

return asyncController.BeginExecute(RequestContext, asyncCallback, asyncState);

}

catch {

factory.ReleaseController(asyncController);

throw;

}

};

EndInvokeDelegate endDelegate = delegate(IAsyncResult asyncResult) {

try {

asyncController.EndExecute(asyncResult);

}

finally {

factory.ReleaseController(asyncController);

}

};

SynchronizationContext syncContext = SynchronizationContextUtil.GetSynchronizationContext();

AsyncCallback newCallback = AsyncUtil.WrapCallbackForSynchronizedExecution(callback, syncContext);

return AsyncResultWrapper.Begin(newCallback, state, beginDelegate, endDelegate, _processRequestTag);

}

else {

// synchronous controller

Action action = delegate {

try {

controller.Execute(RequestContext);

}

finally {

factory.ReleaseController(controller);

}

};

return AsyncResultWrapper.BeginSynchronous(callback, state, action, _processRequestTag);

}

});

}

protectedinternalvirtualvoid EndProcessRequest(IAsyncResult asyncResult) {

SecurityUtil.ProcessInApplicationTrust(() => {

AsyncResultWrapper.End(asyncResult, _processRequestTag);

});

}

privatestaticstring GetMvcVersionString() {

// DevDiv 216459:

// This code originally used Assembly.GetName(), but that requires FileIOPermission, which isn't granted in

// medium trust. However, Assembly.FullName *is* accessible in medium trust.

returnnew AssemblyName(typeof(MvcHandler).Assembly.FullName).Version.ToString(2);

}

protectedvirtualvoid ProcessRequest(HttpContext httpContext) {

HttpContextBase iHttpContext = new HttpContextWrapper(httpContext);

ProcessRequest(iHttpContext);

}

protectedinternalvirtualvoid ProcessRequest(HttpContextBase httpContext) {

SecurityUtil.ProcessInApplicationTrust(() => {

IController controller;

IControllerFactory factory;

ProcessRequestInit(httpContext, out controller, out factory);

try {

controller.Execute(RequestContext);

}

finally {

factory.ReleaseController(controller);

}

});

}

privatevoid ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory) {

// If request validation has already been enabled, make it lazy. This allows attributes like [HttpPost] (which looks

// at Request.Form) to work correctly without triggering full validation.

bool? isRequestValidationEnabled = ValidationUtility.IsValidationEnabled(HttpContext.Current);

if (isRequestValidationEnabled == true) {

ValidationUtility.EnableDynamicValidation(HttpContext.Current);

}

AddVersionHeader(httpContext);

RemoveOptionalRoutingParameters();

// Get the controller type

string controllerName = RequestContext.RouteData.GetRequiredString("controller");

// Instantiate the controller and call Execute

factory = ControllerBuilder.GetControllerFactory();

controller = factory.CreateController(RequestContext, controllerName);

if (controller == null) {

thrownew InvalidOperationException(

String.Format(

CultureInfo.CurrentCulture,

MvcResources.ControllerBuilder_FactoryReturnedNull,

factory.GetType(),

controllerName));

}

}

privatevoid RemoveOptionalRoutingParameters() {

RouteValueDictionary rvd = RequestContext.RouteData.Values;

// Get all keys for which the corresponding value is 'Optional'.

// ToArray() necessary so that we don't manipulate the dictionary while enumerating.

string[] matchingKeys = (from entry in rvd

where entry.Value == UrlParameter.Optional

select entry.Key).ToArray();

foreach (string key in matchingKeys) {

rvd.Remove(key);

}

}

#region IHttpHandler Members

bool IHttpHandler.IsReusable {

get {

return IsReusable;

}

}

void IHttpHandler.ProcessRequest(HttpContext httpContext) {

ProcessRequest(httpContext);

}

#endregion

#region IHttpAsyncHandler Members

IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) {

return BeginProcessRequest(context, cb, extraData);

}

void IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) {

EndProcessRequest(result);

}

#endregion

}

public class MvcHandler : IHttpAsyncHandler, IHttpHandler, IRequiresSessionState {
private static readonly object _processRequestTag = new object();
private ControllerBuilder _controllerBuilder;

internal static readonly string MvcVersion = GetMvcVersionString();
public static readonly string MvcVersionHeaderName = "X-AspNetMvc-Version";

public MvcHandler(RequestContext requestContext) {
if (requestContext == null) {
throw new ArgumentNullException("requestContext");
}

RequestContext = requestContext;
}

internal ControllerBuilder ControllerBuilder {
get {
if (_controllerBuilder == null) {
_controllerBuilder = ControllerBuilder.Current;
}
return _controllerBuilder;
}
set {
_controllerBuilder = value;
}
}

public static bool DisableMvcResponseHeader {
get;
set;
}

protected virtual bool IsReusable {
get {
return false;
}
}

public RequestContext RequestContext {
get;
private set;
}

protected internal virtual void AddVersionHeader(HttpContextBase httpContext) {
if (!DisableMvcResponseHeader) {
httpContext.Response.AppendHeader(MvcVersionHeaderName, MvcVersion);
}
}

protected virtual IAsyncResult BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, object state) {
HttpContextBase iHttpContext = new HttpContextWrapper(httpContext);
return BeginProcessRequest(iHttpContext, callback, state);
}

protected internal virtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state) {
return SecurityUtil.ProcessInApplicationTrust(() => {
IController controller;
IControllerFactory factory;
ProcessRequestInit(httpContext, out controller, out factory);

IAsyncController asyncController = controller as IAsyncController;
if (asyncController != null) {
// asynchronous controller
BeginInvokeDelegate beginDelegate = delegate(AsyncCallback asyncCallback, object asyncState) {
try {
return asyncController.BeginExecute(RequestContext, asyncCallback, asyncState);
}
catch {
factory.ReleaseController(asyncController);
throw;
}
};

EndInvokeDelegate endDelegate = delegate(IAsyncResult asyncResult) {
try {
asyncController.EndExecute(asyncResult);
}
finally {
factory.ReleaseController(asyncController);
}
};

SynchronizationContext syncContext = SynchronizationContextUtil.GetSynchronizationContext();
AsyncCallback newCallback = AsyncUtil.WrapCallbackForSynchronizedExecution(callback, syncContext);
return AsyncResultWrapper.Begin(newCallback, state, beginDelegate, endDelegate, _processRequestTag);
}
else {
// synchronous controller
Action action = delegate {
try {
controller.Execute(RequestContext);
}
finally {
factory.ReleaseController(controller);
}
};

return AsyncResultWrapper.BeginSynchronous(callback, state, action, _processRequestTag);
}
});
}

protected internal virtual void EndProcessRequest(IAsyncResult asyncResult) {
SecurityUtil.ProcessInApplicationTrust(() => {
AsyncResultWrapper.End(asyncResult, _processRequestTag);
});
}

private static string GetMvcVersionString() {
// DevDiv 216459:
// This code originally used Assembly.GetName(), but that requires FileIOPermission, which isn't granted in
// medium trust. However, Assembly.FullName *is* accessible in medium trust.
return new AssemblyName(typeof(MvcHandler).Assembly.FullName).Version.ToString(2);
}

protected virtual void ProcessRequest(HttpContext httpContext) {
HttpContextBase iHttpContext = new HttpContextWrapper(httpContext);
ProcessRequest(iHttpContext);
}

protected internal virtual void ProcessRequest(HttpContextBase httpContext) {
SecurityUtil.ProcessInApplicationTrust(() => {
IController controller;
IControllerFactory factory;
ProcessRequestInit(httpContext, out controller, out factory);

try {
controller.Execute(RequestContext);
}
finally {
factory.ReleaseController(controller);
}
});
}

private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory) {
// If request validation has already been enabled, make it lazy. This allows attributes like [HttpPost] (which looks
// at Request.Form) to work correctly without triggering full validation.
bool? isRequestValidationEnabled = ValidationUtility.IsValidationEnabled(HttpContext.Current);
if (isRequestValidationEnabled == true) {
ValidationUtility.EnableDynamicValidation(HttpContext.Current);
}

AddVersionHeader(httpContext);
RemoveOptionalRoutingParameters();

// Get the controller type
string controllerName = RequestContext.RouteData.GetRequiredString("controller");

// Instantiate the controller and call Execute
factory = ControllerBuilder.GetControllerFactory();
controller = factory.CreateController(RequestContext, controllerName);
if (controller == null) {
throw new InvalidOperationException(
String.Format(
CultureInfo.CurrentCulture,
MvcResources.ControllerBuilder_FactoryReturnedNull,
factory.GetType(),
controllerName));
}
}

private void RemoveOptionalRoutingParameters() {
RouteValueDictionary rvd = RequestContext.RouteData.Values;

// Get all keys for which the corresponding value is 'Optional'.
// ToArray() necessary so that we don't manipulate the dictionary while enumerating.
string[] matchingKeys = (from entry in rvd
where entry.Value == UrlParameter.Optional
select entry.Key).ToArray();

foreach (string key in matchingKeys) {
rvd.Remove(key);
}
}

#region IHttpHandler Members
bool IHttpHandler.IsReusable {
get {
return IsReusable;
}
}

void IHttpHandler.ProcessRequest(HttpContext httpContext) {
ProcessRequest(httpContext);
}
#endregion

#region IHttpAsyncHandler Members
IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) {
return BeginProcessRequest(context, cb, extraData);
}

void IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) {
EndProcessRequest(result);
}
#endregion
}

值得一提的是，在MVC3中已经实现异步处理(IHttpAsyncHandler)

8、StopRoutingHandler类

表示一个“不处理URL的路由处理类”， 比如MVC在RouteCollection类型上扩展了一个IgnoreRoute方法，用于指示路由系统忽略处理指定的url。其实现方式是生成一个Route对象，指定其RouteHandler属性为一个StopRoutingHandler对象。

9、IRouteConstraint接口

用于构建Route.Constraints属性，表示一个约束条件。Match方法用于检查url是否符合路由规则，符合返回true，否则false。