错误500

500jspserver

解决方案 »

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很明显空指针错，第32行的list可能没取到值，是用的request.getAttribute()取的吗，或者把完整的jsp页面贴出来
<%@ page language="java" contentType="text/html; charset=UTF-8" %>
<%@ page import="lvjianyu.blog.Blog" %>
<%@ page import="lvjianyu.blog.Comment" %>
<%@ page import="java.util.List" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>显示博文</title>
</head><body>
<% Blog blog=(Blog)request.getAttribute("blog");
List list=(List)request.getAttribute("commentList");
%>
<table width="781" height="329" border="0">
  <tr>
    <td height="30"><div align="center"><%=blog.getTitle()%></div></td>
  </tr>
  <tr>
    <td height="168"><%=blog.getContent() %></td>
  </tr>
  <tr>
    <td height="50"><%=blog.getCreatedTime() %></td>
  </tr>
  <tr>
    <td> </td>
  </tr>
    <tr>
    <td height="66">

<% for(int i=0;i<list.size();i++){
Comment comment=(Comment)list.get(i);
  %>
    <table width="672" border="1">
      <tr>
        <td>评论人：<%=comment.getUsername() %></td>
        </tr>
      <tr>
        <td><%=comment.getContent() %></td>
        </tr>
      <tr>
        <td>评论时间</td>
        </tr>
    </table>
    <br></br>
<%} %>
    <p> </p></td>
  </tr>
  <tr>
    <td height="28"><form id="form1" method="post" action="/blog/servlet/CommentServlet">
    <input type="hidden" name="method" value="add"/>
    <input type="hidden" name="blog_id" value="<%=blog.getId()%>"/>
      <table width="668" border="1">
        <tr>
          <td width="84">评论人：</td>
          <td width="568"><label for="name"></label>
            <input name="name" type="text" id="name" size="20" /></td>
        </tr>
        <tr>
          <td>内容：</td>
          <td><label for=""></label>
            <textarea name="content" cols="80" rows="10" id="content"></textarea></td>
        </tr>
        <tr>
          <td><input type="submit" name="button" id="button" value="提交" /></td>
          <td> </td>
        </tr>

      </table>
    </form></td>
  </tr>


</table>
</body>
</html>
是，本人小白，  怎么改呀   具体一点谢谢！
找出来了，list 为空~ 添加一个判断语句就OK了！  谢谢！
list 为空，类似这种循环之前都必须有判断的