攔截asp.net輸出流并進行處理的方法
本文實例主要實現(xiàn)對已經(jīng)生成了HTML的頁面做一些輸出到客戶端之前的處理。
方法的實現(xiàn)原理是:把Response的輸出重定向到自定義的容器內(nèi),也就是我們的StringBuilder對象里,在HTML所有的向頁面輸出都變成了向StringBuilder輸出,然后我們對StringBuilder處理完成之后,再把Response的輸出重定向到原來的頁面上,然后再通過Response.Write方法把StringBuilder的內(nèi)容輸出到頁面上。
這里之所以用反射,是因為Response對象的OutPut屬性是只讀的,通過反編譯該類的程序集發(fā)現(xiàn),OutPut實際上是內(nèi)部私有成員 _writer來實現(xiàn)輸出的。因此通過反射來改寫該成員的值以實現(xiàn)輸出流的重定向。
具體功能代碼如下:
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,用來獲取頁面內(nèi)容 var type_rp = context.Response.GetType(); //通過反射獲取對象的私有字段 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(xiàn):
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,用來獲取頁面內(nèi)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(); } }
相信本文所述對大家的asp.net程序設(shè)計有一定的借鑒價值。
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