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拦截asp.net输出流做处理, 拦截HTML文本

2024-08-07 15:10:15   209人阅读

对已经生成了HTML的页面做一些输出到客户端之前的处理

 

方法的原理是：把Response的输出重定向到自定义的容器内，也就是我们的StringBuilder对象里，在HTML所有的向页面输出都变 成了向StringBuilder输出，然后我们对StringBuilder处理完成之后，再把Response的输出重定向到原来的页面上，然后再通 过Response.Write方法把StringBuilder的内容输出到页面上

 

这里之所以用反射，是因为Response对象的OutPut属性是只读的，通过反编译该类的程序集发现，OutPut实际上是内部私有成员 _writer来实现输出的。因此通过反射来改写该成员的值以实现输出流的重定向。（测试过第三种方法，可行）

    using System;      using System.Collections.Generic;      using System.Linq;      using System.Web;      using System.Web.UI;      using System.Web.UI.WebControls;      using System.Text;      using System.IO;      using System.Reflection;            public partial class _Default : System.Web.UI.Page       {          StringBuilder content = new StringBuilder();          TextWriter tw_old, tw_new;          FieldInfo tw_field;                protected void Page_Load(object sender, EventArgs e)          {              var context = HttpContext.Current;                    tw_old = context.Response.Output;//Response原来的OutPut              tw_new = new StringWriter(content);//一个StringWriter,用来获取页面内容              var type_rp = context.Response.GetType();              //通过反射获取对象的私有字段              tw_field = type_rp.GetField("_writer", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);              tw_field.SetValue(context.Response, tw_new);          }                protected override void Render(HtmlTextWriter writer)          {              base.Render(writer);              //替换回Response的OutPut              tw_field.SetValue(HttpContext.Current.Response, tw_old);              //做自己的处理              content.AppendLine("<!--江湖小子-->");              HttpContext.Current.Response.Write(content.ToString());          }      }            方法二，用HttpModul来实现：            using System;      using System.Collections.Generic;      using System.Linq;      using System.Web;      using System.Web.UI;      using System.IO;      using System.Text;      using System.Reflection;            /// <summary>      ///HttpModule 的摘要说明      /// </summary>      public class HttpModule : IHttpModule      {          private HttpApplication _contextApplication;          private TextWriter tw_new, tw_old;          private StringBuilder _content;          private FieldInfo tw_field;                public void Init(HttpApplication context)          {              _contextApplication = context;              _contextApplication.PreRequestHandlerExecute += new EventHandler(_contextApplication_PreRequestHandlerExecute);          }                public void Dispose()          {              _contextApplication = null;              _contextApplication.Dispose();          }                public void _contextApplication_PreRequestHandlerExecute(object sender, EventArgs e)          {              HttpContext context = _contextApplication.Context;                    var _page = context.Handler as System.Web.UI.Page;              _page.Unload += new EventHandler(_page_Unload);                    _content = new StringBuilder();              tw_old = context.Response.Output;//Response原来的OutPut              tw_new = new StringWriter(_content);//一个StringWriter,用来获取页面内容              var type_rp = context.Response.GetType();              tw_field = type_rp.GetField("_writer", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);              tw_field.SetValue(context.Response, tw_new);          }                      void _page_Unload(object sender, EventArgs e)          {              //替换回Response的OutPut              tw_field.SetValue(HttpContext.Current.Response, tw_old);              //做自己的处理              _content.AppendLine("<!--江湖小子-->");              HttpContext.Current.Response.Write(_content.ToString());          }            }            方法三：      public class HttpModule : IHttpModule      {          private HttpApplication _contextApplication;          private TextWriter tw_new, tw_old;          private StringBuilder _content;          private FieldInfo tw_field;                public void Init(HttpApplication application)          {              _contextApplication = application;              _contextApplication.BeginRequest += new EventHandler(_contextApplication_BeginRequest);              _contextApplication.EndRequest +=new EventHandler(_contextApplication_EndRequest);          }                void _contextApplication_BeginRequest(object sender, EventArgs e)          {              _content = new StringBuilder();              tw_old = _contextApplication.Response.Output;              tw_new = new StringWriter(_content);              var type_rp = _contextApplication.Response.GetType();              tw_field = type_rp.GetField("_writer", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);              tw_field.SetValue(_contextApplication.Response, tw_new);          }                void _contextApplication_EndRequest(object sender, EventArgs e)          {              tw_field.SetValue(_contextApplication.Response, tw_old);              //做自己的处理              _content.AppendLine("<!--jhxz-->");              _contextApplication.Response.Write(_content.ToString());          }                public void Dispose()          {              _contextApplication = null;              _contextApplication.Dispose();          }      }

 

拦截asp.net输出流做处理, 拦截HTML文本


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