java - 我的 JDBC select 准备语句有什么问题？

Question

这个问题已经有答案了:

right syntax to use near '?' (3 个回答)

已关闭 7 年前。

我正在尝试在 java 中调试我准备好的语句，但我陷入了这个 checkEmail我实现的功能。当我进入调试状态时，它达到 setString行，它显示 NOT SPECIFIED 代替 '?' 。如果我硬编码'findEmail'进入字符串查询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);