我的 JDBC 选择准备好的语句有什么问题？ [复制]

Question

我正在尝试在 java 中调试我准备好的语句，但我被困在我实现的这个 checkEmail 函数上。当我进入调试并到达setString 行时，它显示未指定代替'?'。如果我将'findEmail' 硬编码到字符串查询中，它将起作用并找到电子邮件。这是一段代码：

public static boolean checkEmail(String findEmail) {
    Connection conn = EstablishConnection.conn;
    boolean found = false;
    try {
        String query = "SELECT email FROM customers WHERE email=?";
        Logging.debug(query);
        PreparedStatement preparedStatement = conn.prepareStatement(query);
        preparedStatement.setString(1,findEmail);
        ResultSet rs = preparedStatement.executeQuery(query);
        //Iterate through the results of the query
        if (rs.next()) {
            found = true;
        }
        preparedStatement.close();
    } catch (Exception e) {
        Logging.debug("Exception thrown in CustomerOperations.getCustomerInfo(): " + e.getMessage());
        e.printStackTrace();
    }
    return found;

}

Answer 1

尝试替换这个：

  ResultSet rs = preparedStatement.executeQuery(query);

与：

  ResultSet rs = preparedStatement.executeQuery();

因为您已经将查询传递给prepareStatement：conn.prepareStatement(query);