一个简单问题 jsp数据库操作 - Java / Web 开发

帮忙看看
  sql = "insert into user values(null,?,?)";
cn = dbc.getCn();
pstm = dbc.getPstm(cn,sql);
try {
pstm.setString(1,"a");
pstm.setString(2,"a");
pstm.executeUpdate();
response.sendRedirect("/BBS/login.jsp");
} catch (SQLException e1) {
e1.printStackTrace();
}catch (IOException e) {
e.printStackTrace();
}
帮忙看看 ，报java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).异常

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谢谢。已解决了