攔截asp.net輸出資料流做處理, 攔截HTML文本

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對已經產生了HTML的頁面做一些輸出到用戶端之前的處理

 

方法的原理是：把Response的輸出重新導向到自訂的容器內，也就是我們的StringBuilder對象裡，在HTML所有的向頁面輸出都變 成了向StringBuilder輸出，然後我們對StringBuilder處理完成之後，再把Response的輸出重新導向到原來的頁面上，然後再通 過Response.Write方法把StringBuilder的內容輸出到頁面上

 

這裡之所以用反射，是因為Response對象的OutPut屬性是唯讀，通過反編譯該類的程式集發現，OutPut實際上是內部私人成員 _writer來實現輸出的。因此通過反射來改寫該成員的值以實現輸出資料流的重新導向。（測試過第三種方法，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原來的OutPut              tw_new = new StringWriter(content);//一個StringWriter,用來擷取頁面內容              var type_rp = context.Response.GetType();              //通過反射擷取對象的私人欄位              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);              //替換回Response的OutPut              tw_field.SetValue(HttpContext.Current.Response, tw_old);              //做自己的處理              content.AppendLine("<!--江湖小子-->");              HttpContext.Current.Response.Write(content.ToString());          }      }            方法二，用HttpModul來實現：            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 的摘要說明      /// </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原來的OutPut              tw_new = new StringWriter(_content);//一個StringWriter,用來擷取頁面內容              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)          {              //替換回Response的OutPut              tw_field.SetValue(HttpContext.Current.Response, tw_old);              //做自己的處理              _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);              //做自己的處理              _content.AppendLine("<!--jhxz-->");              _contextApplication.Response.Write(_content.ToString());          }                public void Dispose()          {              _contextApplication = null;              _contextApplication.Dispose();          }      }  

 

攔截asp.net輸出資料流做處理, 攔截HTML文本