Question

在我的Java程序中，我无法运行Addplaylist.java文件。它打开很好......但是我能够add a playlist我需要数据库中每个member的名字！

我已经添加了一些System.out.println("")'s来检查我在文件中的位置，并且由于某种原因，我只会将其转到addPlaylist() GUI。我已经尝试调试它并找到错误但我找不到它！

这个文件是从main GUI调用的 - 我知道数据库中有值，并且连接正常，因为我在另一个文件中使用过它。

这是我的addPlaylist.java：

package GUI;

import DBconnection.connection;


import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextArea;
import javax.swing.JTextField;

/**
 *
 * @author james
 */
public class addPlaylist extends JFrame implements ActionListener{
    private Container mainCon = this.getContentPane();
    private JPanel formPanel = new JPanel();
    private JPanel paidPanel = new JPanel();

    /*ALL USER INPUT FIELDS*************************/
    //Buttons
    private static JButton submitPlaylist = new JButton("Add Playlist");

    /*TEXT FIELDS BOXES *******************************/
    private JLabel lblPlaylistName = new JLabel("Playlist Name: ");
    private JTextField txtPlaylistName = new JTextField("", 15);
    /*TEXT FIELDS BOXES *******************************/

    /*COMBO BOXES *******************************/
    private JLabel lblNames = new JLabel();
    private JComboBox comNames = new JComboBox();
    /*COMBO BOXES *******************************/

    /*DECLARED VARIABLES ****************************/
    //    private String membersData = "";
    /*DECLARED VARIABLES ****************************/

    public addPlaylist(){
        super("Add a Playlist");
        this.setBounds(400, 500, 315,400);
        mainCon.add(formPanel);

        /** BEGINNING OF FORM ************/
        formPanel.add(lblPlaylistName);
        formPanel.add(txtPlaylistName);

        //Combobox (Names)
        formPanel.add(lblNames);
        formPanel.add(comNames);
        //comNames.addActionListener(this);

        //txtPlaylistName.addActionListener(this);
        System.out.println("In add playlist");
    }

    public void actionPerformed(ActionEvent action) {
        System.out.println("In Action Performed");
        /**ADD DATABASE CONNECTIONS*****************/
        /****** Set the default code - needed for SQL statements *************/
        Connection conDB = null;
        Statement stmt = null;
        ResultSet membersData = null;

        /** GET MYSQL DETAILs ---------**/
        String url = connection.geturl();
        String username = connection.getUsername();
        String password = connection.getPassword();


        try{
            System.out.println("In Try Statement");
             /****** DEFAULT MYSQL DRIVERS **************************/
            //load the MYSQL driver
                Class.forName(connection.getDriver());
                conDB = DriverManager.getConnection(url, username, password);
                //create statement
                stmt = conDB.createStatement();
            /****** DEFAULT MYSQL DRIVERS **************************/

            String sqlSelect = "SELECT membId, name, memberType FROM members";
            membersData = stmt.executeQuery(sqlSelect);
            System.out.println("After executed");


            while(membersData.next()){
//                comNames.addItem(membersData.getString("name"));
                System.out.println("In while loop");
                String membId = membersData.getString("membId");
                System.out.println(membId);

     //            System.out.println(membersData.getString("name"));
     //            System.out.println(membersData.getString("memberType"));
            }
            //membersData.close();
        }
        catch(SQLException er){
            System.out.println("Error was: " + er);
        } catch (ClassNotFoundException ex) {
            System.out.println("SECOND ERROR: " + ex);
        }
    }  
}

Answer 1

因此，要解决此问题，我所做的就是将Combo box所需的所有代码都包含在名为Database connections and result sets etc...的函数中的showCombo()中。然后我在showCombo()方法中调用addPlaylist() { }。

像这样：

public void showCombo(){
            /****** Set the default code - needed for SQL statements *************/
        Connection conDB = null;
        Statement stmt = null;
        ResultSet membersData = null;



        /** GET MYSQL DETAILs ---------**/
        String url = connection.geturl();
        String username = connection.getUsername();
        String password = connection.getPassword();


        try{
            System.out.println("In Try Statement");
             /****** DEFAULT MYSQL DRIVERS **************************/
            //load the MYSQL driver
                Class.forName(connection.getDriver());
                conDB = DriverManager.getConnection(url, username, password);
                //create statement
                stmt = conDB.createStatement();
            /****** DEFAULT MYSQL DRIVERS **************************/

            String sqlSelect = "SELECT membId, name, memberType FROM members";
            membersData = stmt.executeQuery(sqlSelect);
            System.out.println("After executed");



            while(membersData.next()){
                comNames.addItem(membersData.getString("name"));
//                System.out.println("In while loop");
//                String membId = membersData.getString("membId");
//                System.out.println(membId);

//                System.out.println(membersData.getString("name"));
//                System.out.println(membersData.getString("memberType"));
            }
            //membersData.close();
        }
        catch(SQLException er){
            System.out.println("Error was: " + er);
        } catch (ClassNotFoundException ex) {
            System.out.println("SECOND ERROR: " + ex);
        }
        }

数据库不会显示结果？

1 个答案: