jsp访问数据库中出现的问题？？？
这几天我初学使用纯jdbc连接sqlserver2005数据库，jdbc驱动配置完成，在java下测试程序完全正常，但是在jsp下面，却爆出了异常。org.apache.jasper.JasperException: An exception occurred processing JSP page /SqlTest.jsp at line 20
17:
18:
19: String sql="select * from S;";
20: Class.forName(DB_driver);
21: Connection con=DriverManager.getConnection(DB_url,DB_user,DB_pwd);
22: Statement stmt=con.createStatement();
23: ResultSet rs=stmt.executeQuery(sql);
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:524)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:417)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause
javax.servlet.ServletException: java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:850)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:779)
org.apache.jsp.SqlTest_jsp._jspService(SqlTest_jsp.java:100)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause
java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1358)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)
org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:128)
org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:66)
java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
java.lang.Class.forName0(Native Method)
java.lang.Class.forName(Class.java:169)
org.apache.jsp.SqlTest_jsp._jspService(SqlTest_jsp.java:73)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
上面这些就是出现的异常，好像说加载驱动出现问题，但是在java下测试时通过的，所以请各位大神指教？？？？？？？
