日期:2014-05-18  浏览次数:20645 次

自定义标签-众高手帮我看下,这个问题出在哪,该如何解决?急!
最近开始学习“自定义标签”,但在最后运行的时候出现了异常,代码如下:
test.jsp:
<%@   page   contentType= "text/html;   charset=GBK "   %>
<!DOCTYPE   HTML   PUBLIC   "-//W3C//DTD   HTML   4.01   Transitional//EN ">
<!DOCTYPE   taglib   PUBLIC   "-//W3C//DTD   HTML   4.01   Transitional//EN ">
<%@   taglib   uri= "/WEB-INF/mytag.tld "   prefix= "mytag "%>
<html>
    <head>
        <title> My   JSP   'Test.jsp '   starting   page </title>
    </head>

    <body>
        This   is   my   JSP   page.   <br>
        Date   :   <mytag:demo   parameter= "date "   /> <br>
        File   :   <mytag:demo   parameter= "filename "   />
    </body>
</html>
-------------------------------------------
DemoTag.java:
package   jsp;

import   java.util.Date;

import   javax.servlet.http.*;
import   javax.servlet.jsp.*;
import   javax.servlet.jsp.tagext.*;

public   class   DemoTag   extends   TagSupport   {

    public   int   doStartTag()   throws   JspException   {
        try   {
            HttpServletRequest   request   =   (HttpServletRequest)pageContext.getRequest();
            JspWriter   out   =   pageContext.getOut();

            if   (parameter.compareToIgnoreCase( "filename ")   ==   0)
                out.print(request.getServletPath());
            else
                out.print(new   Date());

        }   catch   (java.io.IOException   e)   {
            throw   new   JspTagException(e.getMessage());
        }

        return   SKIP_BODY;
    }

    private   String   parameter   =   "date ";

    public   void   setParameter(String   parameter)   {
        this.parameter   =   parameter;
    }

    public   String   getParameter()   {
        return   parameter;
    }
}
-----------------------------------------
web.xml:
<?xml   version= "1.0 "   encoding= "UTF-8 "?>
<web-app   xmlns= "http://java.sun.com/xml/ns/j2ee "   xmlns:xsi= "http://www.w3.org/2001/XMLSchema-instance "   xsi:schemaLocation= "http://java.sun.com/xml/ns/j2ee   http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd "   version= "2.