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jsp hash地图 get 异常,请高手帮助

热度:5040   发布时间:2013-02-25 21:16:00
jsp hashmap get 错误,请高手帮助
不知道为什么会报错:root causejava.lang.NullPointerException

org.apache.jsp.liuyan2_jsp._jspService(liuyan2_jsp.java:100) 

org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) 

javax.servlet.http.HttpServlet.service(HttpServlet.java:803) 




 页面代码如下:<link rel="stylesheet" type="text/css" href="mycss2.css" />

<body>

<% int page_count = 1;

 int row = 5;

 int sum_page = 1;

 Messagebean mbean = new Messagebean();

 int sum_row = mbean.getallcount();

 System.out.println("sum_row"+sum_row);

 System.out.println(page_count);

 HashMap map = mbean.getallmessage(page_count, row);

%>

<div id="main">

  <div id="lcol">

  <div class="lbox"><div class="h2">你好,欢迎登陆</div>

  <div class="lboxpic"><img src="images/center_onepiece.jpg"></div>

  <div class="lboxpic"><img src="images/center_onepiece.jpg" /></div>

  <div class="lboxpic"><img src="images/center_onepiece.jpg"></div>

  <div class="lboxpic"><img src="images/center_onepiece.jpg"></div>

  </div>

  </div>

 <div id="rcol">

  <table width="90%" border="0" cellpadding="0" cellspacing="0">

  <%

  List list = (List) map.get("all");

  System.out.println("wangkang4");

  for (int i=0;i<list.size();i++)

  {System.out.println(list.get(i));

  }

  if (list.size() < 1) {

  %>

  <p align="center">目前没有留言 </p>

  <%

  }

  for (int i = 0; i < list.size(); i++) {

  Message me = (Message) list.get(i);

  %>

  <tr>

  <td class="context">

  <table width="100%" border="0" cellpadding="0"> <tr> <td><strong><%=me.getname()%></strong></td></tr>

  <tr>

  <td><strong><%=me.getcontext()%></strong></td>

  </tr> </table> </td> </tr>

  <% } %> </table> </div> </div>

 </body>


package com.jsp.bean;

import com.jsp.util.*;

  import java.text.SimpleDateFormat;

public class Messagebean {

Connection con = null;

public boolean Insertmessage(Message message)

{略……

}

public HashMap getallmessage(int page_count,int row)  

{

HashMap map = new HashMap();

List list = new ArrayList();

con=DataBaseConnection.getConnection();

String sql="select * from message order by id desc limit "+(page_count-1)*row+","+row;

Statement st=null;

ResultSet rs = null;

System.out.println("wangkang");

try {

 System.out.println("wangkang3");

 st=con.createStatement();

 rs=st.executeQuery(sql);

 while(rs.next())
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