Response.Redirect 原理及实现

发布时间：2020-08-04 11:00:16 阅读：940 作者：tongling_zzu 栏目：编程语言

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之前一直以为Response.Redirect （“default1.aspx”）的运行原理是这样的 Response.Redirect 原理及实现

但经过断点测试发现不是，当程序执行到Response.Redirect （“default1.aspx”）；时下边会跳转到default1.aspx下的Page_Load（）方法中。也就是说2，3根本没有运行，只有1跟4，浏览器在根据4返回的状态码来在前台地址栏显示出不同的url，说到这里了咱们就反编译一把Response.Redirect看看里面的具体实现：

internalvoidRedirect(string url, bool endResponse, bool permanent)
{
    if (url == null)
    {
        thrownewArgumentNullException("url");
    }
    if (url.IndexOf('\n') >= 0)
    {
        thrownewArgumentException(SR.GetString("Cannot_redirect_to_newline"));
    }
    if (this._headersWritten)
    {
        thrownewHttpException(SR.GetString("Cannot_redirect_after_headers_sent"));
    }
    Pagepage = this._context.HandlerasPage;
    if ((page != null) && page.IsCallback)
    {
        thrownewApplicationException(SR.GetString("Redirect_not_allowed_in_callback"));
    }
    url = this.ApplyRedirectQueryStringIfRequired(url);
    url = this.ApplyAppPathModifier(url);
    url = this.ConvertToFullyQualifiedRedirectUrlIfRequired(url);
    url = this.UrlEncodeRedirect(url);
    this.Clear();
    if (((page != null) && page.IsPostBack) && (page.SmartNavigation && (this.Request["__smartNavPostBack"] == "true")))
    {
        this.Write("<BODY><ASP_SMARTNAV_RDIR url=\"");
        this.Write(HttpUtility.HtmlEncode(url));
        this.Write("\"></ASP_SMARTNAV_RDIR>");
        this.Write("</BODY>");
    }
    else
    {
        this.StatusCode = permanent ? 0x12d : 0x12e;
        this.RedirectLocation = url;
        if (UriUtil.IsSafeScheme(url))
        {
            url = HttpUtility.HtmlAttributeEncode(url);
        }
        else
        {
            url = HttpUtility.HtmlAttributeEncode(HttpUtility.UrlEncode(url));
        }
        this.Write("<html><head><title>Object moved</title></head><body>\r\n");
        this.Write("<h3>Object moved to <a href=\"" + url + "\">here</a>.</h3>\r\n");
        this.Write("</body></html>\r\n");
    }
    this._isRequestBeingRedirected = true;
    EventHandlerredirecting = Redirecting;
    if (redirecting != null)
    {
        redirecting(this, EventArgs.Empty);
    }
    if (endResponse)
    {
        this.End();
    }
}

其中由37，38行的

this.StatusCode = permanent ? 0x12d : 0x12e;

this.RedirectLocation = url;

可以看出状态码和跳转地址是在这里赋值的，我邪恶的感觉到扩展IhttpModule可以拦截http状态码，使用js代码段来实现http页面的跳转，代码如下：

using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
namespace ClassLibrary2
{
    public class Class1 : System.Web.IHttpModule
    {
        public void Init(HttpApplication application)
        {
            application.PreSendRequestHeaders += new EventHandler(application_PreSendRequestHeaders);
        }
        private void application_PreSendRequestHeaders(object sender, EventArgs e)
        {
            HttpApplication Application = (HttpApplication) sender;
            HttpContext context = Application.Context;
            if (context.Response.StatusCode == 302)
            {
                context.Response.Write("<script>window.open(’" + context.Response.RedirectLocation + "’)</script>");
                context.Response.StatusCode = 200;
            }
        }
    }
}

然后再配置一下web.config

<?xml version="1.0"?>
　　<configuration>
　　<system.web>
　　<compilation debug="true"/>
　　<authentication mode="Windows"/>
　　<httpModules>
　　<add name="MyModule" type="ClassLibrary2.Class1,ClassLibrary2"></add>
　　</httpModules>
　　</system.web>
　　</configuration>

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Response.Redirect 原理及实现

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