看了很多篇关于tomcat的安装，还是不能解决我的问题

我来简单的描述一下，我可以看到本地的tomcat服务器，也就是我可以看得到，完后我把jsp的应用放到webapps里面，可是访问相应的jsp却显示如下信息。已经很久了，不知道怎么解决，高手帮我
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type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException
        org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
        org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
        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.NullPointerException
        sun.jdbc.odbc.JdbcOdbcDriver.initialize(JdbcOdbcDriver.java:436)
        sun.jdbc.odbc.JdbcOdbcDriver.connect(JdbcOdbcDriver.java:153)
        java.sql.DriverManager.getConnection(DriverManager.java:525)
        java.sql.DriverManager.getConnection(DriverManager.java:193)
        com.guestbook.DBConnection.getConnectionToAccess(DBConnection.java:31)
        org.apache.jsp.index_jsp._jspService(index_jsp.java:82)
        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)


note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.　　　　　　
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