Tutorial on binding a second-level domain name to a specific controller instance

This article mainly introduces how to bind the second-level domain name to a specific controller in Asp.net Core MVC. Friends who need it can refer to it

Application scenarios: Enterprise portals will set up different sections according to different content, such as Sina has sports, entertainment channels, etc. In some cases, it is necessary to set up different second-level domain names for different sections, such as Sina Sports sports.sina.com.cn.

In asp.net core mvc, if you want to achieve the effect of sections, you may create different controllers for different sections (of course there are other technologies, the quality of the implementation is not discussed here), in In this case, how to bind a unique second-level domain name to the controller. For example, the controller corresponding to the sports channel is called SportController. When accessing the system through the sports.XXX.com domain name, directly enter the SportController and pass this second-level domain name. The domain name cannot access other controllers.

　 Having finished the scenario above, let’s take a look at how to implement it.

There is routing rule configuration in asp.net core mvc. The configuration is in the Startup.Configure method. The specific code is as follows:

app.UseMvc(routes =>
{
   routes.MapRoute(
      name: "default",
      template: "{controller=Home}/{action=Index}/{id?}",
      defaults: new { area="admin"});
});

Unfortunately, support for domain names is not supported (what I understand so far is that if there are any problems, you are welcome to correct me). Register routing rules through routes.MapRouter and add them to RouteCollection. When a request comes, RouterCollection loops through all registered IRouter objects until the first matching IRouter is found. Although the framework does not support domain name configuration rules, we can implement an IRouter ourselves to implement the logic of second-level domain name judgment. I temporarily named it SubDomainRouter. The specific implementation code is as follows:

public class SubDomainRouter : RouteBase
 {
   private readonly IRouter _target;
   private readonly string _subDomain;
   public SubDomainRouter(
     IRouter target,
     string subDomain,//当前路由规则绑定的二级域名
     string routeTemplate,
     RouteValueDictionary defaults,
     RouteValueDictionary constrains,
     IInlineConstraintResolver inlineConstraintResolver)
     : base(routeTemplate,
        subDomain,
        inlineConstraintResolver,
        defaults,
        constrains,
        new RouteValueDictionary(null))
   {
     if (target == null)
     {
       throw new ArgumentNullException(nameof(target));
     }
     if (subDomain == null)
     {
       throw new ArgumentNullException(nameof(subDomain));
     }
     _subDomain = subDomain;
     _target = target;
   }
   public override Task RouteAsync(RouteContext context)
   {
     string domain = context.HttpContext.Request.Host.Host;//获取当前请求域名，然后跟_subDomain比较，如果不想等，直接忽略
     if (string.IsNullOrEmpty(domain) || string.Compare(_subDomain, domain) != 0)
     {
       return Task.CompletedTask;
     }
　　　　　　
　　　　 //如果域名匹配，再去验证访问路径是否匹配
     return base.RouteAsync(context);
   }
   protected override Task OnRouteMatched(RouteContext context)
   {
     context.RouteData.Routers.Add(_target);
     return _target.RouteAsync(context);
   }
   protected override VirtualPathData OnVirtualPathGenerated(VirtualPathContext context)
   {
     return _target.GetVirtualPath(context);
   }
 }

From the above code we only see domain name detection, but how to direct the domain name to a specific controller requires us to do some work when registering this IRouter and directly enter the code:

public static class RouteBuilderExtensions
  {    public static IRouteBuilder MapDomainRoute(
      this IRouteBuilder routeBuilder,string domain,string area,string controller)
    {
      if(string.IsNullOrEmpty(area)||string.IsNullOrEmpty(controller))
      {
        throw new ArgumentNullException("area or controller can not be null");
      }
      var inlineConstraintResolver = routeBuilder
        .ServiceProvider
        .GetRequiredService<IInlineConstraintResolver>();
        string template = "";
          RouteValueDictionary defaults = new RouteValueDictionary();
          RouteValueDictionary constrains = new RouteValueDictionary();
          constrains.Add("area", area);
          defaults.Add("area", area);
          constrains.Add("controller", controller);
          defaults.Add("controller", string.IsNullOrEmpty(controller) ? "home" : controller);
          defaults.Add("action", "index");
          template += "{action}/{id?}";//路径规则中不再包含控制器信息，但是上面通过constrains限定了查找时所要求的控制器名称
          routeBuilder.Routes.Add(new SubDomainRouter(routeBuilder.DefaultHandler, domain, template, defaults, constrains, inlineConstraintResolver));
      return routeBuilder;
    }
}

Finally, we can register the corresponding rules in Startup, as follows:

##

public static class RouteBuilderExtensions
  {    public static IRouteBuilder MapDomainRoute(
      this IRouteBuilder routeBuilder,string domain,string area,string controller)
    {
      if(string.IsNullOrEmpty(area)||string.IsNullOrEmpty(controller))
      {
        throw new ArgumentNullException("area or controller can not be null");
      }
      var inlineConstraintResolver = routeBuilder
        .ServiceProvider
        .GetRequiredService<IInlineConstraintResolver>();
        string template = "";
          RouteValueDictionary defaults = new RouteValueDictionary();
          RouteValueDictionary constrains = new RouteValueDictionary();
          constrains.Add("area", area);
          defaults.Add("area", area);
          constrains.Add("controller", controller);
          defaults.Add("controller", string.IsNullOrEmpty(controller) ? "home" : controller);
          defaults.Add("action", "index");
          template += "{action}/{id?}";//路径规则中不再包含控制器信息，但是上面通过constrains限定了查找时所要求的控制器名称
          routeBuilder.Routes.Add(new SubDomainRouter(routeBuilder.DefaultHandler, domain, template, defaults, constrains, inlineConstraintResolver));
      return routeBuilder;
    }
}

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