.Net MVC5路由机制与扩展

新建一个MVC项目启动后,首先访问的地址是http://localhost:xxx/Home/Index,这时候我们也明白因为在程序中有个叫做Home的控制器,并且在这个控制器下面有个叫做Index的方法,基于这种对应的关系,才有了这种结果,那么这种对应关系是如何产生,如何工作的了?

在我们网站在第一次启动的时候,会去访问一个全局的配置文件Global.asax下面的Application_Start()方法,代码如下

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;

namespace Test
{
    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);
        }
    }
}

在这个方法中就注册了我们的路由配置,相关的注册文件都是在在App_Start目录下

 路由配置文件RouteConfig.cs,内容如下

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;

namespace Test
{
    public class RouteConfig
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

            routes.MapRoute(
                name: "Default",
                url: "{controller}/{action}/{id}",
                defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
            );
        }
    }
}

首先是忽略路由,满足匹配会被忽略,如果没有特殊需求,这个地方就不需要更改,

name表示路由的名称,同一个路由集合中,路由名称必须唯一,不能够有重名,

url就是正则表达式,用于http://localhost:xxx/后路径地址的匹配,

defaults表示缺省路由,也就是默认的路由.这是一个路由规则增删的方法,并且默认的路由为home/index,

还有一个比较常用的参数是constraints,用于条件约束,简单实例如下:

    public class RouteConfig
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

            //假若Home下有Test(int year,int month,int day)方法
            //home/Test_2017_06_05可以访问至该方法
            //home/Test_2017_6_05是无法访问
            routes.MapRoute(
              name: "Constraints",
              url: "{controller}/{action}_{year}_{month}_{day}",
              defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional },
              //条件参数,约束后面参数(此处简单正则:4位数字,2位数字,2位数字)
              constraints: new { year = @"^d{4}", month = @"^d{2}", day = @"^d{2}" });

            routes.MapRoute(
                name: "Default",
                url: "{controller}/{action}/{id}",
                defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional });
        }
    }

路由浅析

那么路由究竟是如何工作的,下面是2个与路由工作十分紧密的2个方法的源码,任何http请求进入后,都会先被它们处理

public virtual void PostResolveRequestCache(HttpContextBase context)
    {
        RouteData routeData = RouteCollection.GetRouteData(context);
        if (routeData != null)
        {
            IRouteHandler routeHandler = routeData.RouteHandler;
            if (routeHandler == null)
            {
                throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.GetString("UrlRoutingModule_NoRouteHandler")));
            }
            if (!(routeHandler is StopRoutingHandler))
            {
                RequestContext requestContext = new RequestContext(context, routeData);
                context.Request.RequestContext = requestContext;
                IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);
                if (httpHandler == null)
                {
                    throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[1]
                    {
                        routeHandler.GetType()
                    }));
                }
                if (httpHandler is UrlAuthFailureHandler)
                {
                    if (FormsAuthenticationModule.FormsAuthRequired)
                    {
                        UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this);
                        return;
                    }
                    throw new HttpException(401, SR.GetString("Assess_Denied_Description3"));
                }
                context.RemapHandler(httpHandler);
            }
        }
    }

public RouteData GetRouteData(HttpContextBase httpContext)
{
    if (httpContext == null)
    {
        throw new ArgumentNullException("httpContext");
    }
    if (httpContext.Request == null)
    {
        throw new ArgumentException(SR.GetString("RouteTable_ContextMissingRequest"), "httpContext");
    }
    if (base.Count == 0)
    {
        return null;
    }
    bool flag = false;
    bool flag2 = false;
    if (!RouteExistingFiles)
    {
        flag = IsRouteToExistingFile(httpContext);
        flag2 = true;
        if (flag)
        {
            return null;
        }
    }
    using (GetReadLock())
    {
        foreach (RouteBase item in this)
        {
            RouteData routeData = item.GetRouteData(httpContext);
            if (routeData != null)
            {
                if (!item.RouteExistingFiles)
                {
                    if (!flag2)
                    {
                        flag = IsRouteToExistingFile(httpContext);
                        flag2 = true;
                    }
                    if (flag)
                    {
                        return null;
                    }
                }
                return routeData;
            }
        }
    }
    return null;
}

大致分析下这段源码,我们可以得出下列比较重要的结论

1在路由匹配之前,先一步检查了物理文件的存在,所以mvc和webform可以共存,如果存在满足路径条件的aspx文件,它会优先被访问

2路由是从上到下逐个匹配的,所以排列的顺序对于路由匹配是非常重要的

 路由扩展

在上述基础下,我们对路由有了大概的了解,对此我们可以简单扩展一下

路由并不是只能够在路径规则上做文章,我们也可以继承路由的基类RouteBase自定义一些路由,然后把自定义的路由放入注册路由集合中,调准好顺序,实现我们想要的结果.因为能够得到HttpContext这个用户请求的上下文,我们可以完成很多扩展,例如检查ip,浏览器类型,参数等等,下面我们就简单的实现不同浏览器访问到不同路径的功能,如下:

    public class RouteConfig
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

            //注意顺序
            routes.Add("Agent",new Agent());

            routes.MapRoute(
                name: "Default",
                url: "{controller}/{action}/{id}",
                defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional });
        }

      
    }
    public class Agent : RouteBase
    {
        public override RouteData GetRouteData(HttpContextBase httpContext)
        {
            if (httpContext.Request.UserAgent.Contains("Chrome/63.0.3239.132"))
            {
                var data = new RouteData(this, new MvcRouteHandler());
                data.Values.Add("controller", "Home");
                data.Values.Add("action", "About");
                return data;
            }
            else
            {
                return null;
            }
        }

        public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
        {
            return null;
        }
    }

一定得注意路由排列的顺序,如果将上面的Agent路由放在Default路由后面,那么就直接会访问到Home/Index,而不会去判断.

我们也可以通过自定义继承了RouteBase的Route类,来完成特殊路径的扩展,如下

  public class RouteConfig
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

            routes.Add(new Route("Test",new TestRouteHandler()));

            routes.MapRoute(
                name: "Default",
                url: "{controller}/{action}/{id}",
                defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional });
        }
    }

    public class TestRouteHandler : IRouteHandler
    {
        public IHttpHandler GetHttpHandler(RequestContext requestContext)
        {
            return new TestHandler();
        }
    }
    public class TestHandler : IHttpHandler
    {
        public bool IsReusable => true;

        public void ProcessRequest(HttpContext context)
        {
            context.Response.Write("Test");
        }
    }

效果如下:

出自:博客园-半路独行

 原文地址:https://www.cnblogs.com/banluduxing/p/9185159.html

 本文出自于http://www.cnblogs.com/banluduxing 转载请注明出处。