拦截asp.net输出流并进行处理的方法

本文实例主要实现对已经生成了HTML的页面做一些输出到客户端之前的处理。

方法的实现原理是：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。

具体功能代码如下：

usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Web;
usingSystem.Web.UI;
usingSystem.Web.UI.WebControls;
usingSystem.Text;
usingSystem.IO;
usingSystem.Reflection;
publicpartialclass_Default:System.Web.UI.Page
{
StringBuildercontent=newStringBuilder();
TextWritertw_old,tw_new;
FieldInfotw_field;
protectedvoidPage_Load(objectsender,EventArgse)
{
varcontext=HttpContext.Current;

tw_old=context.Response.Output;//Response原来的OutPut
tw_new=newStringWriter(content);//一个StringWriter,用来获取页面内容
vartype_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);
}
protectedoverridevoidRender(HtmlTextWriterwriter)
{
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：  

usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Web;
usingSystem.Web.UI;
usingSystem.IO;
usingSystem.Text;
usingSystem.Reflection;
///<summary>
///HttpModule的摘要说明
///</summary>
publicclassHttpModule:IHttpModule
{
privateHttpApplication_contextApplication;
privateTextWritertw_new,tw_old;
privateStringBuilder_content;
privateFieldInfotw_field;
publicvoidInit(HttpApplicationcontext)
{
_contextApplication=context;
_contextApplication.PreRequestHandlerExecute+=newEventHandler(_contextApplication_PreRequestHandlerExecute);
}
publicvoidDispose()
{
_contextApplication=null;
_contextApplication.Dispose();
}
publicvoid_contextApplication_PreRequestHandlerExecute(objectsender,EventArgse)
{
HttpContextcontext=_contextApplication.Context;

var_page=context.HandlerasSystem.Web.UI.Page;
_page.Unload+=newEventHandler(_page_Unload);

_content=newStringBuilder();
tw_old=context.Response.Output;//Response原来的OutPut
tw_new=newStringWriter(_content);//一个StringWriter,用来获取页面内容
vartype_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(objectsender,EventArgse)
{
//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：

publicclassHttpModule:IHttpModule
{
privateHttpApplication_contextApplication;
privateTextWritertw_new,tw_old;
privateStringBuilder_content;
privateFieldInfotw_field;
publicvoidInit(HttpApplicationapplication)
{
_contextApplication=application;
_contextApplication.BeginRequest+=newEventHandler(_contextApplication_BeginRequest);
_contextApplication.EndRequest+=newEventHandler(_contextApplication_EndRequest);
}
void_contextApplication_BeginRequest(objectsender,EventArgse)
{
_content=newStringBuilder();
tw_old=_contextApplication.Response.Output;
tw_new=newStringWriter(_content);
vartype_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(objectsender,EventArgse)
{
tw_field.SetValue(_contextApplication.Response,tw_old);
//做自己的处理
_content.AppendLine("<!--jhxz-->");
_contextApplication.Response.Write(_content.ToString());
}
publicvoidDispose()
{
_contextApplication=null;
_contextApplication.Dispose();
}
}

相信本文所述对大家的asp.net程序设计有一定的借鉴价值。