hibernate数据库操作，总是报空指针异常

if (user.getUsername().length() > 0) {
String hql = "select * from user where username = : username ";
query = ses.createQuery(hql); //这一行总是报错，是不是查不到数据库有东西
query.setParameter("username",username);
List User rt = query.list();
if(rt!=null){ req.setAttribute("register_error", "用户已经注册了!");
return "error"; } }

貌似是因为HQL不能使用select * 的原因？
select u from user u where username = : username试试？或者用createSQLQuery

String hql = "select * from user where username = : username "; hql中的user是实体类吧

你这样子可以的，3q