[database connection] - excerpt from training

This note is mainly about using java Connect mysql database , Realize the addition, deletion, modification and query of the database .

The picture shows the general framework of the experiment ：

Running results ：
Code and explanation of each part ：

1. DBconnector

package Dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DBconnector {
//java Connect to database 
	private static final String DBDRIVER = "com.mysql.cj.jdbc.Driver"; //  Drive string 
	private static final String DBURL = "jdbc:mysql://localhost:3306/grate";//  Connect URL
	private static final String DBUSER = "root"; //  user name 
	private static final String DBPASSWORD = "123456"; //  password 
	public static Connection getConnection() {
		Connection conn = null;
		// Abnormal judgment 
		try {
			Class.forName(DBDRIVER);// The load driver 
			// Get the connection 
			conn = (Connection) DriverManager.getConnection(DBURL, DBUSER, DBPASSWORD);
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println(" Abnormal driver loading ");
		}
		catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println(" Abnormal connection ");
		}
		return conn;
	}

}

2. Add_users( increase )

package Dao_users;


import Dao.DBconnector;

import javax.swing.*;
import java.awt.*;
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.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class Add_users extends JDialog implements ActionListener{
	/*
	 *  implements Serializable , For Cross Version translation 
	 */
	private static final long SerialVersionUID =1L;

	private JPanel jp1,jp2;	// Situation distribution panel .

	JLabel JL=new JLabel(" Add student information ",JLabel.CENTER);// Create master label 

//JLabel     JTextField
	JLabel JLSno= new JLabel(" Student number :");
	JTextField JTSno= new JTextField();

	JLabel JLSname= new JLabel(" full name :");
	JTextField JTSname= new JTextField();

	JLabel JLSsex= new JLabel(" Gender :");
	JTextField JTSsex= new JTextField();

	JLabel JLSage= new JLabel(" Age :");
	JTextField JTSage= new JTextField();

	JLabel JLSdept= new JLabel(" college :");
	JTextField JTSdept= new JTextField();

	//  Three buttons 
	JButton JB1=new JButton(" add to ");
	JButton JB2=new JButton(" Reset ");
	JButton JB3=new JButton(" sign out ");
	
	// picture 
	ImageIcon image=new ImageIcon("D:\\ Little spongebobsquarepants .png");
	JLabel label=new JLabel(image);

	//  Create connection data method 
	String sql="";
	// Create a constructor 
	public Add_users()
	{
		Container c = this.getContentPane();
		jp1 = new JPanel();

		//  Set window size 
		this.setSize(700,450);
		this.setLocationRelativeTo(null);
		this.setVisible(true);

		//  add to 
		this.setTitle(" Add student information ");
		this.setLayout(null);// Set the window layout manager to null, use setBounds() Method to set the component location 

		//JL.setFont(new Font(" Song style ",Font.PLAIN,30));
		//JL.setBounds(100,40,200,40);
		//jp1.add(JL);

		// Layout 
		
		JLSno.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSno.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSno.setBounds(50,50,100,30);
		this.add(JLSno);
		JTSno.setBounds(150,50,150,30);
		this.add(JTSno);

		JLSname.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSname.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSname.setBounds(370,50,100,30);
		this.add(JLSname);
		JTSname.setBounds(470,50,150,30);
		this.add(JTSname);

		JLSsex.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSsex.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSsex.setBounds(50,125,100,30);
		this.add(JLSsex);
		JTSsex.setBounds(150,125,150,30);
		this.add(JTSsex);

		JLSage.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSage.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSage.setBounds(350,125,120,30);
		this.add(JLSage);
		JTSage.setBounds(470,125,150,30);
		this.add(JTSage);

		JLSdept.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSdept.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSdept.setBounds(200,200,100,30);
		this.add(JLSdept);
		JTSdept.setBounds(300,200,150,30);
		this.add(JTSdept);

		//  Three buttons 
		JB1.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB2.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB3.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB1.setBounds(80,320,120,40);
		this.add(JB1);
		JB1.addActionListener(this);
		JB2.setBounds(280,320,120,40);
		this.add(JB2);
		JB2.addActionListener(this);
		JB3.setBounds(480,320,120,40);
		this.add(JB3);
		JB3.addActionListener(this);

		// picture 
		this.setLayout(null);
		this.add(label);
		label.setBounds(0,0,700,450);

		addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e)
			{
				dispose();
			}
		});

	}
	public void actionPerformed(ActionEvent e) {
		if(e.getSource()==JB1)
		{
			users users=new users();// Instantiate objects 
			users.setSno(JTSno.getText());
			users.setSname(JTSname.getText());
			users.setSsex(JTSsex.getText());
			users.setSage(JTSage.getText());
			users.setSdept(JTSdept.getText());

			sql="select * from student where Sno='"+users.getSno()+"'";
			//sql="select * from student where Sno=123";
			// Connect to database 
			DBconnector conn=new DBconnector();
			Connection con=conn.getConnection();
			// establish Statement object 
			try {
				Statement stmt=(Statement) con.createStatement();
				ResultSet rs= (ResultSet) stmt.executeQuery(sql);
				System.out.println("OK!");
				if(rs.next())
				{
					JOptionPane.showMessageDialog(null," The student number already exists ");
					rs.close();
				}
				else{
					sql="insert into student(Sno,Sname,Ssex,Sage,Sdept) "
							+ "values('"+users.getSno()+"','"+users.getSname()+"','"+users.getSsex()+"','"+users.getSage()+"','"+
							users.getSdept()+"');";//   String type put sql A double quotation mark and a single quotation mark are unified in the statement . Pay attention to the semicolon .
					int i=stmt.executeUpdate(sql);
					if(i>0)
					{
						JOptionPane.showMessageDialog(null," Add success ");
					}
					else{
						JOptionPane.showMessageDialog(null," Add failure ");
					}
				}
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
		}
		else if(e.getSource()==JB2)
		{
			JTSno.setText(null);
			JTSname.setText(null);
			JTSsex.setText(null);
			JTSage.setText(null);
			JTSdept.setText(null);
		}
		else if(e.getSource()==JB3)
		{
			this.setVisible(false);
		}

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

3. Delete_users( Delete )

// Delete... According to student number

package Dao_users;

import Dao.DBconnector;
import javax.swing.*;
import java.awt.*;
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.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class Delete_users extends JFrame implements ActionListener{

	private static final long serialVersionUID=1L;

	ImageIcon image=new ImageIcon("D:\\ Little spongebobsquarepants .png");
	JLabel label=new JLabel(image);
	//  title 
	JLabel JL=new JLabel(" Delete basic information ",JLabel.CENTER);
	//
	JLabel JLSno= new JLabel(" Student number :");
	JTextField JTSno= new JTextField();


	JButton JB1=new JButton(" Delete ");
	JButton JB2=new JButton(" Reset ");
	JButton JB3=new JButton(" sign out ");

	String sql="";
	// Define the constructor 
	public Delete_users()
	{
		// Settings window 
		this.setTitle(" Delete student information ");
		this.setSize(700,450);
		this.setLocationRelativeTo(null);
		this.setLayout(null);
		this.setVisible(true);

		this.setLayout(null);
		this.add(label);
		label.setBounds(0,0,700,260);

		//  Set topic information 
		JL.setForeground(Color.red);
		JL.setFont(new Font(" Song style ",Font.PLAIN,19));
		JL.setBounds(150,30,200,40);
		this.add(JL);

		//
		JLSno.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSno.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSno.setBounds(200,280,100,30);
		this.add(JLSno);
		JTSno.setBounds(300,280,150,30);
		this.add(JTSno);

		//  Three buttons 
		JB1.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB2.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB3.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB1.setBounds(80,340,120,40);
		this.add(JB1);
		JB1.addActionListener(this);
		JB2.setBounds(280,340,120,40);
		this.add(JB2);
		JB2.addActionListener(this);
		JB3.setBounds(480,340,120,40);
		this.add(JB3);
		JB3.addActionListener(this);

		addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e)
			{
				dispose();
			}
		});
	}

	public void actionPerformed(ActionEvent e) {
		if(e.getSource()==JB1)
		{
			users users=new users();// Instantiate objects 
			users.setSno(JTSno.getText());

			sql="select * from student where Sno="+users.getSno();
			DBconnector conn=new DBconnector();
			Connection con=conn.getConnection();
			try {
				Statement stmt=(Statement) con.createStatement();
				ResultSet rs=(ResultSet) stmt.executeQuery(sql);
				if(rs.next())// If the query result exists 
				{
					sql="delete from student where Sno="+users.getSno();
					int n=stmt.executeUpdate(sql);// to update 
					if(n>0)JOptionPane.showMessageDialog(null, " Delete successful ");
					else JOptionPane.showMessageDialog(null, " Delete failed ");
				}
				else
				{
					rs.close();
					JOptionPane.showMessageDialog(null, " This student does not exist ");
				}
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
		}
		else if(e.getSource()==JB2)
		{
			JTSno.setText(null);
		}
		else
		{
			this.setVisible(false);// Hide the current window 
		}

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

4. Get_users( check )

package Dao_users;

import Dao.DBconnector;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Vector;

public class Get_users extends JFrame{
	private static final long serialVersionUID = 1L;

	// Store all information 
	Vector all=new Vector();
	// Store header information vector 
	Vector tablehead=new Vector();

	JLabel JL=new JLabel(" Query students' basic information ",JLabel.CENTER);
	JScrollPane jsl=new JScrollPane();// Set the scroll panel 

	JLabel JLSno= new JLabel(" Student number :");
	JTextField JTSno= new JTextField();

	JLabel JLSname= new JLabel(" full name :");
	JTextField JTSname= new JTextField();

	JLabel JLSsex= new JLabel(" Gender :");
	JTextField JTSsex= new JTextField();

	JLabel JLSage= new JLabel(" Age :");
	JTextField JTSage= new JTextField();

	JLabel JLSdept= new JLabel(" college :");
	JTextField JTSdept= new JTextField();

	//  Define construction method 
	//  Establish a database connection 
	String sql="";
	public Get_users()
	{

		//this.setLayout(null);
		//this.add(label);
		//label.setBounds(100,100,1000,700);

		//  Database query statements 
		sql="select * from student;";
		// Connect to database 
		DBconnector conn=new DBconnector();
		Connection con=(Connection) conn.getConnection();
		ResultSet rs=null;
		Statement stmt;
		try {
			stmt = (Statement) con.createStatement();
			rs=(ResultSet) stmt.executeQuery(sql);

			tablehead.add(" Student number ");
			tablehead.add(" name ");
			tablehead.add(" Gender ");
			tablehead.add(" Age ");
			tablehead.add(" college ");


			while(rs.next())
			{
				//  Create objects 
				users users=new users();
				users.setSno(rs.getString("Sno"));
				users.setSname(rs.getString("Sname"));
				users.setSsex(rs.getString("Ssex"));
				users.setSage(rs.getString("Sage"));
				users.setSdept(rs.getString("Sdept"));



				Vector vc=new Vector();

				vc.add(users.getSno());
				vc.add(users.getSname());
				vc.add(users.getSsex());
				vc.add(users.getSage());
				vc.add(users.getSdept());
				System.out.println(vc);


				//  Put it all in vc Collection 
				all.add(vc);
			}


			JTable JT=new JTable(all,tablehead);


			JT.setRowHeight(20);// Set table row height 
			JT.setEnabled(false);// The Settings table is not editable 
			jsl.setViewportView(JT);// Displayed in the scroll panel 


			this.add(jsl,BorderLayout.NORTH);
			//this.add(JL); add to 
			this.setTitle(" Check all student information ");
			this.setSize(700,450);
			this.setLocationRelativeTo(null);
			this.setVisible(true);


		} catch (SQLException e1) {
			e1.printStackTrace();
		}

		addWindowListener(new WindowAdapter() {// Set the window listener 
			@SuppressWarnings("unused")
			public void windowsClosing(WindowEvent e)
			{
				dispose();
			}
		});
	}
	public void actionPerformed(ActionEvent e) {


	}


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

5. Update_users( Change )

package Dao_users;

import Dao.DBconnector;

import javax.swing.*;
import java.awt.*;
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.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class Update_users extends JFrame implements ActionListener {

	private static final long SerialVersionUID =1L;

	JLabel JLSno= new JLabel(" Student number :");
	JTextField JTSno= new JTextField();

	JLabel JLSname= new JLabel(" full name :");
	JTextField JTSname= new JTextField();

	JLabel JLSsex= new JLabel(" Gender :");
	JTextField JTSsex= new JTextField();

	JLabel JLSage= new JLabel(" Age :");
	JTextField JTSage= new JTextField();

	JLabel JLSdept= new JLabel(" college :");
	JTextField JTSdept= new JTextField();

	//  Three buttons 
	JButton JB1=new JButton(" add to ");
	JButton JB2=new JButton(" Reset ");
	JButton JB3=new JButton(" sign out ");
	ImageIcon image=new ImageIcon("D:\\ Little spongebobsquarepants .png");
	JLabel label=new JLabel(image);

	//  Create database statement object 
	String sql="";
	public Update_users()
	{
		//  Set window position and size , And add a title 
		this.setSize(700,450);
		this.setLocationRelativeTo(null);
		this.setVisible(true);
		this.setTitle(" Modify student information ");
		//  Set window manager to empty 
		this.setLayout(null);

		//
		JLSno.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSno.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSno.setBounds(50,50,100,30);
		this.add(JLSno);
		JTSno.setBounds(150,50,150,30);
		this.add(JTSno);

		//
		JLSname.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSname.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSname.setBounds(370,50,100,30);
		this.add(JLSname);
		JTSname.setBounds(470,50,150,30);
		this.add(JTSname);



		//
		JLSsex.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSsex.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSsex.setBounds(50,125,100,30);
		this.add(JLSsex);
		JTSsex.setBounds(150,125,150,30);
		this.add(JTSsex);

		//
		JLSage.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSage.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSage.setBounds(350,125,120,30);
		this.add(JLSage);
		JTSage.setBounds(470,125,150,30);
		this.add(JTSage);

		JLSdept.setFont(new Font(" In black ", Font.PLAIN, 30));
		JTSdept.setFont(new Font(" In black ", Font.PLAIN, 30));
		JLSdept.setBounds(200,200,100,30);
		this.add(JLSdept);
		JTSdept.setBounds(300,200,150,30);
		this.add(JTSdept);

		//  Three buttons 
		JB1.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB2.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB3.setFont(new Font(" In black ", Font.PLAIN, 30));
		JB1.setBounds(80,320,120,40);
		this.add(JB1);
		JB1.addActionListener(this);
		JB2.setBounds(280,320,120,40);
		this.add(JB2);
		JB2.addActionListener(this);
		JB3.setBounds(480,320,120,40);
		this.add(JB3);
		JB3.addActionListener(this);

		this.setLayout(null);
		this.add(label);
		label.setBounds(0,0,700,450);


		addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e)
			{
				dispose();
			}
		});
	}
	//  Button event 
	public void actionPerformed(ActionEvent e) {
		if(e.getSource()==JB1)
		{
			users users=new users();// Instantiate objects 
			users.setSno(JTSno.getText());
			users.setSname(JTSname.getText());
			users.setSsex(JTSsex.getText());
			users.setSage(JTSage.getText());
			users.setSdept(JTSdept.getText());
			//  Database query statements 
			sql="select * from student where Sno="+users.getSno();
			// Connect to database 
			DBconnector conn=new DBconnector();
			Connection con=conn.getConnection();
			try {
				Statement stmt=(Statement) con.createStatement();
				ResultSet rs=(ResultSet) stmt.executeQuery(sql);
				if(rs.next())
				{
					sql="update student set Sname='"+users.getSname()+"',Ssex='"+users.getSsex()+"',Sage='"+
							users.getSage()+"',Sdept='"+users.getSdept()+"' where Sno ="+users.getSno();


					int n=stmt.executeUpdate(sql);
					if(n>0)
					{
						JOptionPane.showMessageDialog(null," The update is successful ");
					}
					else
					{
						JOptionPane.showMessageDialog(null, " Update failed ");
					}

				}
				else
				{
					JOptionPane.showMessageDialog(null, " This student number does not exist ");
				}
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
		}
		else if(e.getSource()==JB2)
		{
			JTSno.setText(null);
			JTSname.setText(null);
			JTSsex.setText(null);
			JTSage.setText(null);
			JTSdept.setText(null);
		}
		else if(e.getSource()==JB3)
		{
			this.setVisible(false);
		}


	}

	public static void main(String[] args) {

		new Update_users();
	}

}

6. users

package Dao_users;

public class users {
// Transfer various data 
	public String getSno() {
		return Sno;
	}

	public void setSno(String sno) {
		Sno = sno;
	}

	public String getSname() {
		return Sname;
	}

	public void setSname(String sname) {
		Sname = sname;
	}

	public String getSsex() {
		return Ssex;
	}

	public void setSsex(String ssex) {
		Ssex = ssex;
	}

	public String getSage() {
		return Sage;
	}

	public void setSage(String sage) {
		Sage = sage;
	}

	public String getSdept() {
		return Sdept;
	}

	public void setSdept(String sdept) {
		Sdept = sdept;
	}

// Privatization 
	//  Student number 
	private String Sno;
	//  full name 
	private String Sname;
	//  Gender 
	private String Ssex;
	//  Age 
	private String Sage;
	//  college 
	private String Sdept;
	public users() {
	}

}

// Main interface code

7. employee

package Main;

import Dao_users.Add_users;
import Dao_users.Delete_users;
import Dao_users.Get_users;
import Dao_users.Update_users;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class employee extends JFrame implements ActionListener{


	//  Create four buttons 
	private static final long serialVersionUID = 1L;
	JButton JB1=new JButton();
	JButton JB2=new JButton();
	JButton JB3=new JButton();
	JButton JB4=new JButton();

	ImageIcon image=new ImageIcon("D:\\ Little spongebobsquarepants .png"); // Insert the picture displayed on the interface 
	JLabel label=new JLabel(image);
	String name1 = null;
	public employee(String name)   // Constructor adds content 
	{
		//  title 
		name1 = name;
		this.setTitle(" Student interface management ");
		this.setBackground(Color.DARK_GRAY); // Interface font color 
		this.setLayout(null);
		this.setSize(800,800);            // Run window size 
		this.setLocationRelativeTo(null);
		this.setVisible(true);

		//  Personal information inquiry 
		JB1.setText(" Student information inquiry ");
		JB1.setFont(new Font(" In black ", Font.PLAIN, 20));// Font settings 
		JB1.setBounds(120,420,200,40);// Button position and size settings 
		JB1.addActionListener(this);
		this.add(JB1);

		//  Personal achievement query 
		JB2.setText(" Delete student information ");
		JB2.setFont(new Font(" In black ", Font.PLAIN, 20));
		JB2.setBounds(350,420,200,40);
		JB2.addActionListener(this);
		this.add(JB2);

		//  Change Password 
		JB3.setText(" Student information added ");
		JB3.setFont(new Font(" In black ", Font.PLAIN, 20));
		JB3.setBounds(120,540,200,40);
		JB3.addActionListener(this);
		this.add(JB3);


		JB4.setText(" Student information modification ");
		JB4.setFont(new Font(" In black ", Font.PLAIN, 20));
		JB4.setBounds(350,540,200,40);
		JB4.addActionListener(this);
		this.add(JB4);

		//  Set picture size 
		this.setLayout(null);
		this.add(label);
		label.setBounds(0,0,700,400);

		addWindowListener(new WindowAdapter() {
			public void windowClosing (WindowEvent e)
			{
				dispose();
			}
		});

	}

// Press the button to transfer the information from the corresponding page 
	@Override
	public void actionPerformed(ActionEvent e) {
		//  Query information 
		if(e.getSource()==JB1)
		{
			new Get_users();
		}
		//  Delete the information 
		else if(e.getSource()==JB2)
		{
			new Delete_users();
		}
		//  Add information 
		else if(e.getSource()==JB3)
		{
			new Add_users();

		}
		// Change information 
		else if (e.getSource()==JB4)
		{
			new Update_users();
		}
	}
	public static void main(String[] args) {
		String name  = "111";
		new employee(name);
	}
}

The modified interface ：