if(rs.next()),每次提示都是java.lang.NullPointerException. System.out.println(rs1);输出为n

if(rs.next()),每次提示都是java.lang.NullPointerException. System.out.println(rs1);输出为null.为什么呀.谢谢.新年快乐!
userName=new String(request.getParameter("userName").getBytes("8859_1"));
userPassword=new String(request.getParameter("userPassword").getBytes("8859_1"));
userEmail=request.getParameter("userEmail");
sql2="insert into user(userName,userPassword,userEmail) values('"+ userName +"','"+ userPassword +"','"+ userEmail +"')";
rs1 = registerBean.executeUpdate(sql2);
System.out.println(rs1);
if(!rs1.next()){

rs1.close();
try{
registerBean.closeStmt();
registerBean.closeConn();
msg="the user is existed";
session.putValue("register_message",msg);

[解决办法]

Java code

registerBean.executeUpdate(sql2);