oracle数据库连接问题

<%@ page language="java" contentType="text/html;charset=GBK"%>
<%@ page import="java.sql.*" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'wang.jsp' starting page</title>
    
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">    
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->  </head>
  
  <body>
   <%
     Connection conn=null;
     try{
         Class.forName("oracle.jdbc.driver.oracledriver");
         String URL="jdbc:oracle:thin:@localhost:1521:orcl";
         String user="SYSMAN";
         String password="zsk";
         conn=DriverManager.getConnection(URL,user,password);
         if(!conn.isClosed())
         out.print("已成功连接Oracle数据库<br>");
         }
         catch(SQLException ex){
         out.println(ex.getMessage());
         }
         finally{
         try{
         if(conn!=null)
         conn.close();
         }
         catch(Exception ex){
         }
         } 
     %>
  </body>
</html>
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Exception in JSP: /wang.jsp:3027:    <%
28:      Connection conn=null;
29:      try{
30:          Class.forName("oracle.jdbc.driver.oracledriver");
31:          String URL="jdbc:oracle:thin:@localhost:1521:orcl";
32:          String user="SYSMAN";
33:          String password="zsk";
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:504)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:375)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause javax.servlet.ServletException: oracle.jdbc.driver.oracledriver
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:858)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791)
org.apache.jsp.wang_jsp._jspService(org.apache.jsp.wang_jsp:104)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause java.lang.ClassNotFoundException: oracle.jdbc.driver.oracledriver
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1352)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1198)
org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:127)
org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:65)
java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
java.lang.Class.forName0(Native Method)
java.lang.Class.forName(Class.java:169)
org.apache.jsp.wang_jsp._jspService(org.apache.jsp.wang_jsp:76)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)为什么会出现上面的错误,谢谢!