在myeclipse里运行连接数据库文件没问题,但是发布到服务器上出问题

    代码如下:
    public static void main(String[] args) {
BooksService bs=new BooksService();
Books book=new Books();
book.setBookname("asp.net");
book.setPrice(10.6f);
bs.add(book);
Collection<Books> cl=bs.find();
for(Iterator<Books> iter=cl.iterator();iter.hasNext();){
Books bk=iter.next();
System.out.println(bk.getBookname());
}
}
   运行结果:
   java
   asp.net数据库连接正常,但在servlet里用的这个,在网页上显示org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:522)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
而用jsp直接连接数据库又没有问题
<%@   page   contentType="text/html;charset=gb2312"%>
  <%@   page   import="java.sql.*"%>
  <html>
  <body>
  <%Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver").newInstance();
  String   url="jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=test;SelectMethod=cursor";
  String   user="web";
  String   password="web";//为另一台自己设置的用户名、密码
  Connection conn= DriverManager.getConnection(url,user,password);
  //result = DriverManager.getConnection(url, username, password);
  Statement stmt=conn.createStatement();
  String sql="select   bookname  from   books";
  ResultSet rs=stmt.executeQuery(sql);
  while(rs.next())   {%>
  您的第一个字段内容为：<%=rs.getString(1)%>
  <%}%>
  <%out.print("数据库操作成功，恭喜你");%>
  <%rs.close();
  stmt.close();
  conn.close();
  %>
  </body>
  </html>
显示结果:
您的第一个字段内容为：java 您的第一个字段内容为：asp.net 数据库操作成功，恭喜你
请高手指教

解决方案 »

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这个是servlet的代码吗?
你的Service看看,呵呵!
java.lang.NullPointerException 看看你的哪个对象空了
servlet部分代码
public Collection<Books> populate(ResultSet rs) throws Exception{
List<Books> list=new ArrayList<Books>();
try {
while(rs.next()){
Books books=new Books();
books.setBookid(rs.getLong("bookid"));
books.setBookname(rs.getString("bookname"));
books.setPrice(rs.getFloat("price"));
list.add(books);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
} public Collection<Books> find() {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs=null;
Collection<Books> bookslist=null;
try {
conn=ManagerConnection.getConnection("mssql");
String sql="select * from books";
ps=conn.prepareStatement(sql);
rs=ps.executeQuery();
bookslist=this.populate(rs);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally{
this.close(conn, ps, rs);
}
return bookslist;
}
servlet显示代码
public String show(){
Books books=null;
StringBuilder sb=new StringBuilder();
sb.append("<TABLE width=\"100%\" border=\"1\" align=\"center\" cellPadding=\"0\" cellSpacing=\"0\" borderColor=\"#cedcef\" borderColorDark=\"#ffffff\">\r\n");
sb.append("<tr bgColor=\"#E3efff\">\r\n");
sb.append("<td>bookid</td>\r\n");
sb.append("<td>书名</td>\r\n");
sb.append("<td>价格</td>\r\n");
sb.append(" <td>修改</td>\r\n");
sb.append(" <td>删除</td>\r\n");
sb.append("</tr>\r\n");
Collection<Books> cl=find();
for(Iterator<Books> iter=(Iterator<Books>)cl.iterator();iter.hasNext();){
books=(Books)iter.next();
sb.append("<tr>\r\n");
sb.append("<td>"+books.getBookid()+"</td>\r\n");
sb.append("<td>"+books.getBookname()+"</td>\r\n");
sb.append("<td>"+books.getPrice()+"</td>\r\n");
sb.append(" <td><a href=\"request/booksedit.jsp?bookid="+books.getBookid()+"\">修改</a></td>\r\n");
sb.append(" <td><a href=\"client/booksdel?bookid="+books.getBookid()+"\">删除</a></td>\r\n");
sb.append("</tr>\r\n");
}
sb.append("</table>\r\n");
return sb.toString();
}books.jsp代码
<%@ page contentType="text/html;charset=gb2312" %>
<jsp:useBean id="booksservice" class="service.BooksService" scope="request"/>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    <title>My JSP 'books.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

  </head>
  <body>
  <%
   int count=booksservice.find().size();
   int pagenum=3;
   int totalnum=(((double)count/(double)pagenum)>(count/pagenum)?count/pagenum+1:count/pagenum);
   int currentpage=1;
   if(request.getParameter("page")!=null)
currentpage=Integer.parseInt(request.getParameter("page"));
   out.println("<a href=\"request/booksadd.html\">添加</a><br>");
    out.println(booksservice.show(currentpage,pagenum,null,null));
   if(currentpage>1){
    out.println("<a href=\"show/books.jsp?page=1\">首页</a> ");
    out.println(" <a href=\"show/books.jsp?page=<%=currentpage-1 \">上一页</a>");
    }
    else
    {
     out.println("首页 ");
     out.println("上一页");
    }
    if(totalnum>currentpage){
     out.println("<a href=\"show/books.jsp?page=<%=currentpage+1\">下一页</a> ");
       out.println(" <a href=\"show/books.jsp?page=<%=totalnum \">尾页</a> ");
   }
    else{
    out.println("下一页 ");
     out.println("尾页");
    }
    %>
  </body>
</html>
哦,我没有用servlet,只用了javabean和jsp,以上所说的servlet显示的代码都是用的javabean里的代码.