Question

我试图理解为什么我不能用Java搜索数据库中的多个记录。它是一个Java jsp应用程序，但我似乎很难找出问题所在。我是jsp的初学者，但我相信不会有任何区别

 try{  
  String myDriver = "org.gjt.mm.mysql.Driver";//db driver 
  String myUrl = database;//connect to db
  Class.forName(myDriver);
  Connection conn = DriverManager.getConnection(myUrl, user, password);//authenticating on database
  String query = "SELECT Cus_ID, Cus_name, Cus_surname, Cus_mail, Cus_Address, Cus_telephone FROM customerdb";//mysql select statement 
  PreparedStatement sta = conn.prepareStatement(query); //prepared statement 
  ResultSet rst = sta.executeQuery(query);


     while (rst.next())
  {


    String cusid = rst.getString("Cus_ID"); //variable to retrieve the customer from the database
    String cusn = rst.getString("Cus_name");
    String cussn = rst.getString("Cus_surname");
    String cusm = rst.getString("Cus_mail");
    String cusaddr = rst.getString("Cus_Address");
    String custel = rst.getString("Cus_telephone");


  if(!(customer.equals(cusid))){


      request.setAttribute("al", "user not found");                       
      request.getRequestDispatcher("account.jsp").forward(request, response); //and user will stay on login page


  }if(customer.equals(cusid)){

      System.out.println("hello" + cusid);
      request.setAttribute("ID", cusid);
      request.setAttribute("name", cusn);
      request.setAttribute("surname", cussn);
      request.setAttribute("mail", cusm);
      request.setAttribute("address", cusaddr);
      request.setAttribute("telephone", custel); 

      request.getRequestDispatcher("account.jsp").forward(request, response);
  }else{

  }
  }
}catch(ClassNotFoundException | SQLException | HeadlessException ex) {
            Logger.getLogger(LogInController.class.getName()).log(Level.SEVERE, null, ex);

  }

Answer 1

PreparedStatement#executeQuery()方法不接受任何参数。改变这个：

ResultSet rst = sta.executeQuery(query);

到此：

ResultSet rst = sta.executeQuery();

使用此API时，这是一个常见的错误。您的代码可能还有其他问题，但这应该会有明显的改进。

通过数据库表搜索id Java无法正常工作

1 个答案: