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？？？？？？？