PreparedStatement MySQLSyntaxErrorException使用有效的查詢字符串

Question

我花了好幾個小時看着什麼應該是完美的代碼。該方法的connection.createStatement()版本可以正常工作，但只要我嘗試將其轉換爲更好的connection.prepareStatement()版本，就會引發MySQLSyntaxErrorException並抱怨'？'附近有問題。字符在我的查詢字符串中。該代碼張貼在下面，我根本無法看到它的問題。數據庫字段是VARCHAR並接受字符串，所以這不是問題。

public Discussion getDbDiscussionInstance(String _instanceId) throws SQLException { 

    String qryStr = null; 
    PreparedStatement myStmt = null; 
    ResultSet myRs = null; 

    // Try to build the object with existing data. 
    try { 
     qryStr = "SELECT assignment_id, discussion_id, section_id, user_id, circle_id, breakout_id, title, description, created, due FROM macb_discussions WHERE instance_id=?"; 
     myStmt = connection.prepareStatement(qryStr); 
     myStmt.setString(1, _instanceId); 
     myRs = myStmt.executeQuery(qryStr); 
     if (rs.next()) { 
      this.discussionId = myRs.getString("discussion_id"); 
     } 
    } catch (SQLException e) { 
     dbFunc.catchSQLException(e); 
    } finally { 
     myRs.close(); 
     myStmt.close(); 
    } 
} 

Answer 1

只能使用myStmt.executeQuery();沒有說法，你已經preperad聲明

Answer 2

從文檔，

Statement.executeQuery(String sql)

PreparedStatement.executeQuery()

所以相應地改變你的函數。 myStmt = connection.prepareStatement(qryStr);至

myStmt = connection.prepareStatement();