求助：JSP的一个异常 - 编程论坛

程序代码：

org.apache.jasper.JasperException: Exception in JSP: /mailBoxSave.jsp:33

30:
31:         //mailbox.setReceiveID(1);
32:
33:         boolean isAdd = mangeDB.addMailBox(mailbox);
34:
35:         if(isAdd){
36:             out.println("发送成功，且已经保存至草稿箱");

Stacktrace:
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:506)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:395)
    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
    (ManageDB.java:51)
    (ManageDB.java:68)
    org.apache.jsp.mailBoxSave_jsp._jspService(mailBoxSave_jsp.java:93)
    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:334)
    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/5.5.20 logs.

代码如下：

程序代码：

<%@ page language="java" contentType="text/html; charset=gbk"
    pageEncoding="gbk"%>
<%@ page import="java.sql.*,java.text.*"%>
<jsp:useBean scope="page" id = "mailbox" class = " scope="page" id = "mangeDB" class = " html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
                              "http://www. http-equiv="Content-Type" content="text/html; charset=gbk">
<title>发送成功</title>
</head>
<body>
<%--传进用户姓名的参数--%>

    <%

        //实际是后面应该传入的参数，但是为了检测，我先让它固定为一个值
        String userName = "yuxinabc001";
        int authorID = 7;

        request.setCharacterEncoding("gbk");
        mailbox.setAuthorID(authorID);
        mailbox.setSendName(userName);
        //mailbox.setReceiveName(request.getParameter("receiveName"));
        mailbox.setReceiveName("receiveName");
        mailbox.setTag(1);
        mailbox.setTitle("title");
        mailbox.setContent("content");

        //mailbox.setReceiveID(1);

        boolean isAdd = mangeDB.addMailBox(mailbox);

        if(isAdd){
            out.println("发送成功，且已经保存至草稿箱");
        }else{
            out.println("失败");
        }
    %>
</body>
</html>

其中MailBox类就是一些get,set方法。而且我确定ManageDB类正确，因为另写main检验和数据库的那个类是正确的。
因为本人才接触JSP，所以不是太会，希望得到大家的帮助！我会在线等待，或发到我邮箱：[email=yuxinabc001@]yuxinabc001@[/email]
谢谢大家了！