java.sql.SQLException: 调用中无效的参数这个错误是在结果集循环取出是抛出的。我不明白的是，用连接池才会抛出这个错，用其它的连接就不会？在Weblogic中测试连接池也没有问题。请问这是为什么？代码在下面：
public boolean isLogin(String uid, String pwd) {
    boolean isLogin = false;
    Connection conn = this.getConnection();
    if (conn != null) {
      String sql =
          "select username,pwd from wasuserinfor where userName=? and pwd=?";
      try {
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setString(1, uid);
        ps.setString(2, pwd);
        ResultSet rs = ps.getResultSet();
        while (rs.next()) {
          String userNaem = rs.getString("USERNAME");
          String password = rs.getString("PWD");
          isLogin = true;
        }
      }
      catch (SQLException ex) {
        ex.printStackTrace();
      }
      finally {
        if (conn != null) {
          try {
            conn.close();
          }
          catch (SQLException ex1) {
            ex1.printStackTrace();
          }
        }
      }
    }
    return isLogin;
  }

  private Connection getConnection() {
    Object obj = null;
    try {
      Context ctx = new InitialContext();
      DataSource ds = (DataSource) ctx.lookup("jdbc/oracle");
      return ds.getConnection();
    }
    catch (SQLException ex) {
      return null;
    }
    catch (NamingException ex) {
      return null;
    }
  }
解决办法是看了代码：ResultSet rs = ps.getResultSet();
之前一个要先执行ps.executeQuery();这样就不会有错了。