拦截asp.net输出流做处理
2024-08-22 16:33:07
本文标题是指对已经生成了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。
- 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();
- }
- }
最后还是推荐一篇好文:码农欧洲出差的一点小插曲
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