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URL重写技术在今天已不是什么新鲜的话题了,在Apache服务器提供了名为mod_rewrite的URL重写模块,而在IIS服务器上,也有很多商业的ISAPI 筛选器模块可供使用。然而这对于我们,没有很多的资金或使用的共享服务器,使得以上的方法都不是最佳的解决方案。幸而ASP.NET给我们提供了强大的可扩展性,能让我们自己定义页面的访问规则,很方便实现URL重写。 在ASP.NET中实现URL重写,需要创建HTTP模块(HttpModule)或HTTP处理程序(HttpHandler),通过调用HttpContext的RewritePath方法来近进行URL重写。本篇文章使用的是HTTP模块做的示例。 使用HTTP模块执行URL重写 首先需要定义一个实现了IHttpModule接口的类。IHttpModule接口定义了两个方法需要实现:
1: public virtual void Init(HttpApplication app) 2: {
3: // WARNING! This does not work with Windows authentication! 4: // If you are using Windows authentication, change to app.BeginRequest 5: app.AuthorizeRequest += new EventHandler(this.URLRewriter); 6: }
在URLRewriter方法里的第7行从配置文件里读取URL重写信息,进行处理,如对正则表达式的处理。如您对如何扩展标准的配置文件还不清楚,请看这篇Blog:扩展.NET 2.0标准配置文件 1: protected void URLRewriter(object sender, EventArgs e) 2: {
3: HttpApplication app = (HttpApplication) sender;
4: string requestedPath = app.Request.Path; 5:
6: // get the configuration rules 7: UrlsCollection rules = UrlsConfig.GetConfig().Urls;
8:
9: for (int i = 0; i < rules.Count; i++) 10: {
11: // get the pattern to look for, and Resolve the Url (convert ~ into the appropriate directory) 12: string lookFor = "^" + RewriterUtils.ResolveUrl(app.Context.Request.ApplicationPath, rules[i].VirtualUrl) + "$"; 13:
14: Regex re = new Regex(lookFor, RegexOptions.IgnoreCase); 15: if (re.IsMatch(requestedPath)) 16: {
17: string sendToUrl = RewriterUtils.ResolveUrl(app.Context.Request.ApplicationPath, re.Replace(requestedPath, rules[i].DestinationUrl)); 18: RewriterUtils.RewriteUrl(app.Context, sendToUrl);
19: break; 20: }
21: }
22:
23: }
如果匹配,则调用RewriteUrl方法,将URL分解成路径和查询字符串两部分,以调用HttpContext.RewritePath方法来实现URL的重写。其中对“URL资源的附加路径信息”(如:Http://www.microsoft.com/virdir/page.html/tail 的tail部分)未做处理,直接用String.Empty来表示,如您需要,可以自行扩展一下。 OK,到此为止,一个简单的URL重写程序就初步完成了,但还没有大功告成,还有一个细节的问题需要我们处理一下,就是页面回发后又会在地址栏显示出重写前的地址,也就是真实的地址,影响美观:)。有两种方法可以解决这个问题:
1: public class Form : System.Web.UI.HtmlControls.HtmlForm 2: {
3: /// <summary> 4: /// The RenderAttributes method adds the attributes to the rendered <form> tag. 5: /// We override this method so that the action attribute is not emitted. 6: /// </summary> 7: protected override void RenderAttributes(HtmlTextWriter writer) 8: {
9: // write the form's name 10: writer.WriteAttribute("name", this.Name); 11: base.Attributes.Remove("name"); 12:
13: // write the form's method 14: writer.WriteAttribute("method", this.Method); 15: base.Attributes.Remove("method"); 16:
17: // remove the action attribute 18: base.Attributes.Remove("action"); 19:
20: // finally write all other attributes 21: this.Attributes.Render(writer); 22:
23: if (base.ID != null) 24: writer.WriteAttribute("id", base.ClientID); 25: }
26:
27: }
这个方法直接去掉了form的action属性,所以页面就直接回发给自己了,能够解决问题,但使用起来比较麻烦。想象一下在每个需要重写URL的页面都要去改写form标记,够崩溃的了。
在ASP.NET 2.0中,有个比较干净的诀窍可以用来重写<form>控件的action属性。具体地来说,利用新的ASP.NET 2.0控件适配器扩展架构来定制控件的输出,用提供的值来覆盖action属性的值。这不要求在.aspx页面里做任何编码改动,而只要在/app_browsers文件夹里添加一个.browser文件,注册使用一个控件适配类即可输出新的action属性。 .browser文件 1: <browsers>
2: <browser refID="Default"> 3: <controlAdapters>
4: <adapter controlType="System.Web.UI.HtmlControls.HtmlForm" 5: adapterType="URLRewriter.Form.FormRewriterControlAdapter" /> 6: </controlAdapters>
7: </browser>
8: </browsers>
URLRewriter.Form.cs文件 1: public class FormRewriterControlAdapter : System.Web.UI.Adapters.ControlAdapter 2: {
3: public FormRewriterControlAdapter() 4: {
5: }
6:
7: protected override void Render(HtmlTextWriter writer) 8: {
9: base.Render(new RewriteFormHtmlTextWriter(writer)); 10: }
11: }
12:
13: public class RewriteFormHtmlTextWriter : HtmlTextWriter 14: {
15: public RewriteFormHtmlTextWriter(HtmlTextWriter writer) 16: : base(writer) 17: {
18: base.InnerWriter = writer.InnerWriter; 19: }
20: public RewriteFormHtmlTextWriter(System.IO.TextWriter writer) 21: : base(writer) 22: {
23: base.InnerWriter = writer; 24: }
25:
26: public override void WriteAttribute(string name, string value, bool fEncode) 27: {
28: //If the attribute we are writing is the "action" attribute, and we are not on a sub-control, 29: //then replace the value to write with the raw URL of the request - which ensures that we'll 30: //preserve the PathInfo value on postback scenarios 31: if (name == "action") 32: {
33: HttpContext context = HttpContext.Current;
34: if (context.Items["ActionAlreadyWritten"] == null) 35: {
36: //We will use the Request.RawUrl property within ASP.NET to retrieve the origional 37: //URL before it was re-written. 38: value = context.Request.RawUrl; 39: //Indicate that we've already rewritten the <form>'s action attribute to prevent 40: //us from rewriting a sub-control under the <form> control 41: context.Items["ActionAlreadyWritten"] = true; 42: }
43: }
44: base.WriteAttribute(name, value, fEncode); 45: }
46: }
直接将action属性的值赋予成URL重写后的地址,简单又实惠,何乐而不为呢。 更正:因为我是在VS里直接进行的测试,使用的是VS自带的那个轻量级服务器(ASP.NET Development Server),而没有在IIS下测试。通过刘岛兄的留言,我看到了51aspx的转载,并对这个错误进行了指正,谢谢诸位。 现在经过在IIS下测试,发现自定义的URL后缀是需要在IIS里映射到aspnet_isapi.dll的,我猜想在Development Server中应该是把所以的后缀都映射到aspnet_isapi.dll上了。所以,如果您的空间是在共享的环境中,不太方便修改的话,直接使用aspx为后缀,也不失为一个好方法。 参考文章:
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