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java.lang.NullPointerException错误

摘要: java.lang.NullPointerException错误

我是struts初学者，下面是我写的Actions代码，为什么修改密码每次只能成功5次，之后就了。。高手帮帮忙呀~~

public class SysChangePwdAction extends Action {
private static final long serialVersionUID = 1L;

public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
SysChangePwdForm rf = (SysChangePwdForm) form;
String oldpwd = rf.getOldpwd();
String newpwd = rf.getNewpwd();
String rnewpwd = rf.getRnewpwd();
String username = rf.getUsername();
Connection conn = null;
Statement stmt = null;
String sql = null;
ResultSet rs = null;

ActionForward forward = new ActionForward();
forward = mapping.findForward("undo");
if (!newpwd.equals(rnewpwd)){
forward = mapping.findForward("error");
}
else if(!oldpwd.equals("")){
try{
conn = Pool.getConnection();
stmt = conn.createStatement();
sql = " select * from tbl_sys_admins where pwd = '"+oldpwd+"' and username ='" + username+"'";
rs=stmt.executeQuery(sql);
if (rs != null){
if (rs.next()) {

try{
conn = Pool.getConnection();
stmt = conn.createStatement();
sql = " update tbl_sys_admins set pwd = '"+newpwd+"' where username ='" + username+"'";
stmt.executeQuery(sql);
forward=mapping.findForward("success");
}
catch(Exception e){
forward=mapping.findForward("error");
}
}
else
forward=mapping.findForward("error");
}
else
forward=mapping.findForward("error");
}
catch(Exception e){
forward=mapping.findForward("error");
}
}

return forward;
}
}

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你不关闭连接当然不行了
在finally里
conn.close();

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可以了 谢谢^_^

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