java.sql.SQLException: 調用中無效的參數這個錯誤是在結果集循環取出是拋出的。我不明白的是，用連接池才會拋出這個錯，用其它的連接就不會？在Weblogic中測試連接池也沒有問題。請問這是為什么？代碼在下面：
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;
    }
  }
解決辦法是看了代碼：ResultSet rs = ps.getResultSet();
之前一個要先執行ps.executeQuery();這樣就不會有錯了。