高分求援报错java.lang.NullPointerException

2011-12-22

高分求助报错java.lang.NullPointerExceptionservletpublic void doGet(HttpServletRequest request, Http

高分求助报错java.lang.NullPointerException
servlet

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String action=request.getParameter("action");
if(action==null)
{
action="";
}
if(action.equals("add"))
{
this.addnews(request, response);
}
}

public void addnews(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException
{
RequestDispatcher rd=null;
CNews cmgbean=new CNews();
CNewsdao cmgdao=new CNewsdao();
cmgbean.setStr_NTitle(trans.toChinese(request.getParameter("ntitle")));
cmgbean.setStr_NTime(trans.toChinese(request.getParameter("ntime")));
cmgbean.setStr_NContent(trans.toChinese(request.getParameter("ncontent")));
boolean mark=cmgdao.operateNews("add",cmgbean);
if(!mark)
{
System.out.println("<script>alert('发布失败！！')</script>");
rd=request.getRequestDispatcher("../admin/login.jsp");
rd.forward(request, response);
}
else
{
response.sendRedirect("../admin/message.jsp");
}

}
}

数据库操作类
public boolean operateNews(String operation,CNews single)
{
String sql=null;
if(operation.equals("add"))
{
sql="insert into News values('"+single.getStr_NTitle()+"','"+single.getStr_NTime()+"','"+single.getStr_NContent()+"')";
//sql="insert into News values('"+single.getStr_NContent()+"','"+single.getStr_NTime()+"','"+single.getStr_NTitle()+"')";
}
if(operation.equals("modify"))
{
sql="update News set NTime='"+single.getStr_NTime()+"',NTitle='"+single.getStr_NTitle()+"',NContent='"+single.getStr_NContent()+"' where NId='"+single.getInt_Id()+"'";
}
if(operation.equals("delete"))
{
sql="delete from News where NId='"+single.getInt_Id()+"'";
}
boolean flag=connect.executeUpdate(sql);
return flag;
}

[解决办法]
web.xml贴出来看看
[解决办法]

探讨
boolean flag=connect.executeUpdate(sql);

[解决办法]
boolean flag=connect.executeUpdate(sql);

connect.executeUpdate(sql)的返回值是影响的行数，怎么能用boolean接收呢？
[解决办法]
at com.dao.CNewsdao.operateNews(CNewsdao.java:33)

很明显CNewsdao.java类的33行代码出错，在此类的operateNews方法中，可以去定位下那行代码，
看是调用其它方法还是方法内的错误。
[解决办法]
唉！又是空指针···

[解决办法]
boolean flag=connect.executeUpdate(sql);

connect抛空指针了吧。
[解决办法]

探讨

求解决方法
数据库能连接上

[解决办法]
at com.dao.CNewsdao.operateNews(CNewsdao.java:33)

你具体看看CNewsdao的33行撒，看看到底什么是空。
然后那个变量是哪儿来的，这样一步步找很快就找到了撒
[解决办法]

Java code

boolean flag=connect.executeUpdate(sql);
[解决办法]
探讨
at com.dao.CNewsdao.operateNews(CNewsdao.java:33)

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高分求援 报错java.lang.NullPointerException

高分求援报错java.lang.NullPointerException