Question

如何使用AWT按钮浏览并显示'textfield'中的每个数据库记录？

我正在尝试使用Java表单来浏览数据库记录，这样当按下“下一个”按钮时，每次后续命中都会将下一个数据库记录提取到相应的文本字段中。这段代码的问题是无论我按下下一个按钮多少次，只有第一条记录显示在文本字段中。

我已经阅读了几个线程，if(rs.next())条件在这种情况下工作。什么可能是正确的解决方案，为什么？

PS：我在Problem code begins和Problem code ends内标记了有问题的区域。

import java.awt.Button;
import java.awt.Choice;
import java.awt.Frame;
import java.awt.GridLayout;
import java.awt.Label;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.swing.JOptionPane;

public class ManageEmployees implements ActionListener
{
    Connection con;

    Statement st;

    ResultSet rs;

    Frame f;

    Choice employeeID;

    Button savenewemployeeButton, updateemployeeButton, returndashboardButton, nextButton/*, previousButton, lastButton, firstButton*/;

    Label nameLabel, usernameLabel, addressLabel, contactnumberLabel, passwordLabel, confirmpasswordLabel, selectemployeeLabel;

    TextField nameTextField, usernameTextField, addressTextField, passwordTextField, confirmpasswordTextField;

    ManageEmployees()
        {
            dbconnect();
            initframe();        
        }

    public void dbconnect()
    {
        try{

        Class.forName("com.mysql.jdbc.Driver");

        con=DriverManager.getConnection("jdbc:mysql://localhost:8889/InventoryManagement","root","root");

        st=con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_UPDATABLE);

        String sql="select * from SalesMen";

        rs=st.executeQuery(sql);

        }
        catch(Exception ce)
        {
            ce.printStackTrace();
        }
    }

    public void initframe()
    {
        f=new Frame("Manage Employees");

        selectemployeeLabel=new Label("Select Employee Type:");
        nameLabel=new Label("Employee Name:");
        addressLabel=new Label("Address:");
        usernameLabel=new Label("User Name:");
        passwordLabel=new Label("Password:");
        confirmpasswordLabel=new Label("Confirm Password:");

        employeeID=new Choice();

        employeeID.add("Sales Person");
        employeeID.add("Sales Manager");
        employeeID.add("Inventory Manager");
        employeeID.add("Administrator");

        savenewemployeeButton=new Button("Save New Employee details");
        savenewemployeeButton.addActionListener(this);
        returndashboardButton=new Button("Return to Dashboard");
        returndashboardButton.addActionListener(this);

        nextButton=new Button("Next");
        nextButton.addActionListener(this);

        nameTextField=new TextField(30);
        addressTextField=new TextField(50);
        usernameTextField=new TextField(20);
        passwordTextField=new TextField(15);
        confirmpasswordTextField=new TextField(15);

        f.setLayout(new GridLayout(10,2,0,2));

        f.add(selectemployeeLabel);
        f.add(employeeID);

        f.add(nameLabel);
        f.add(nameTextField);

        f.add(addressLabel);
        f.add(addressTextField);

        f.add(usernameLabel);
        f.add(usernameTextField);

        f.add(passwordLabel);
        f.add(passwordTextField);

        f.add(confirmpasswordLabel);
        f.add(confirmpasswordTextField);

        f.add(returndashboardButton);
        f.add(savenewemployeeButton);
        f.add(nextButton);

        passwordTextField.setEchoChar('*');
        confirmpasswordTextField.setEchoChar('*');

        f.setSize(500,400);
        f.setVisible(true);
        f.setResizable(false);


        f.addWindowListener(new WindowAdapter()
        {

            public void windowClosing(WindowEvent we)
            {
                System.exit(0);
            }
        }
        );
    }

    public void actionPerformed(ActionEvent e)
    {

        // Return to dashboard on button click

        if(e.getSource()==returndashboardButton)
        {
            f.dispose();
            new Dashboard();
        }

        // ---------------------------------------- (Begin) Save new employee information ------------------------------------------------------------//    

       // Save new Sales Person information  

        String salesmen=employeeID.getSelectedItem();


        if(salesmen=="Sales Person" && e.getSource()==savenewemployeeButton)
        {

            try
            {       
                String fullname1=nameTextField.getText();
                String address1=usernameTextField.getText();
                String username1=addressTextField.getText();
                String password1=passwordTextField.getText();

                String sql="insert into SalesMen values('"+fullname1+"','"+address1+"','"+username1+"','"+password1+"')";
                st.executeUpdate(sql);

                JOptionPane.showMessageDialog(null,"New Sales Man's details saved!");

            }

                catch(Exception ce)
                {
                    ce.printStackTrace();
                }

        }

           // Save new Sales Manager information  

        String salesmanager=employeeID.getSelectedItem();

        if(salesmanager=="Sales Manager" && e.getSource()==savenewemployeeButton)
        {
            try
            {

                String fullname1=nameTextField.getText();
                String address1=usernameTextField.getText();
                String username1=addressTextField.getText();
                String password1=passwordTextField.getText();

                String sql="insert into SalesManagers values('"+fullname1+"','"+address1+"','"+username1+"','"+password1+"')";
                st.executeUpdate(sql);

                JOptionPane.showMessageDialog(null,"New Sales Manager's details saved!");

            }
                catch(Exception ce)
                {
                    ce.printStackTrace();
                }
        }

           // Save new Inventory Manger information  


        String inventorymanger=employeeID.getSelectedItem();

        if(inventorymanger=="Inventory Manager" && e.getSource()==savenewemployeeButton)
        {
            try
            {

                String fullname1=nameTextField.getText();
                String address1=usernameTextField.getText();
                String username1=addressTextField.getText();
                String password1=passwordTextField.getText();

                String sql="insert into InventoryManagers values('"+fullname1+"','"+address1+"','"+username1+"','"+password1+"')";
                st.executeUpdate(sql);

                JOptionPane.showMessageDialog(null,"New Inventory Manager's details saved!");

            }

                catch(Exception ce)
                {
                    ce.printStackTrace();
                }
        }

           // Save new Administrator information  


        String administrator=employeeID.getSelectedItem();

        if(administrator=="Administrator" && e.getSource()==savenewemployeeButton)
        {
            try
            {
                String fullname1=nameTextField.getText();
                String address1=usernameTextField.getText();
                String username1=addressTextField.getText();
                String password1=passwordTextField.getText();

                String sql="insert into Administrators values('"+fullname1+"','"+address1+"','"+username1+"','"+password1+"')";
                st.executeUpdate(sql);

                JOptionPane.showMessageDialog(null,"New Admin's details saved!");

            }

                catch(Exception ce)
                {
                    ce.printStackTrace();
                }
            // ---------------------------------------- (End) Save new employee information ------------------------------------------------------------//          
        }

        if(salesmen=="Sales Person" && e.getSource()==nextButton)
        {
                 try
                    {   
                        String sql="select * from SalesMen";
                        rs=st.executeQuery(sql);

                      // Problem code begins 

                        if(rs.next())
                        {

                            nameTextField.setText(rs.getString("FullName")); 
                            usernameTextField.setText(rs.getString("UserName"));
                            addressTextField.setText(rs.getString("Address")); 

                        }

                       else

                        {
                            rs.previous();
                            System.out.println("boo!");
                            JOptionPane.showMessageDialog(null,"No more records");
                        }  

                    }

                           // Problem code ends 

                    catch(Exception ce)
                    {
                        ce.printStackTrace();
                    }


        }

    } 

    public static void main(String[] args) 
    {   
           new ManageEmployees();
    }

}

Answer 1

使用Swing JComponents而不是AWT Components
使用JTable代替AWT TextFields
搜索ResultSetTableModel或TableFromDatabase以获得简单，稳定和正确的解决方法
ResultSetTableModel，TableFromDatabase或您的想法与事件调度线程有问题

Answer 2

好吧，尽管人们给出了有用的答案;经过反复试验，我找到了一个更恰当的答案。如果正确使用，“if（rs.next（））”条件 DOES WORK 可向前导航数据库记录。它与AWT或SWING完美搭配。通过不恰当地放置以下代码行来解决问题：

/ *请记住小心使用并在程序中放置以下代码* /

String sql="select * from Tablename";
rs=st.executeQuery(sql);

因此，在参考本问题中的程序时，请注意在构造函数调用dbconnect（）函数时，在程序生命周期内，上面的两行代码已经被调用过一次。现在要注意，因为这是问题的开始。 *每次点击“下一个按钮”时，上面突出显示的两个字符串被多余触发，因此每次重置结果集，并且逻辑上不允许'rs.next（）'移动到下一个记录。因此，仅在dbconnect（）函数中放置两行代码 一次才能正确完成工作。*

浏览＆amp;使用AWT按钮在“文本字段”中显示每个数据库记录

2 个答案: