调试出错~~JAVABEAN凋用不出来

test.jsp
<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*,java.lang.*" errorPage="" %><html>
<head><title>test@@ go on~!</title></head>
<body>
<center>
<table>
<tr>
<td>ID</td>
<td>item</td>
</tr>
<jsp:useBean id="db" scope="page" class="cosmetic.db"/>
<%! String item;
    int id;%>
<% 
   String  str= "select * from items";
   ResultSet rs = db.executeQuery(str);
   while(rs.next())
  { id=rs.getInt("id");
    item=rs.getString("item");
 %>
<tr>
<td><%=id%></td>
<td><%=item %></td>
</tr>
<%
}
rs.close(); %>
</center>
</body>
</html>

解决方案 »

  1.   

    调试错误：
    exception org.apache.jasper.JasperException
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:358)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
    root cause java.lang.NullPointerException
    org.apache.jsp.test4_jsp._jspService(test4_jsp.java:73)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
      

  2.   

    public boolean executeUpdate(String sql)这一句不要boolean看看行不行
      

  3.   

    hehe..应该跟这个没关系吧～～！　谢谢
    那我删除试试看～！