Creating a Java Project

Adding Required Dependencies

Create a lib directoyr in your project and place the necessary JAR files. The required libraries are available for download.

Implementing Database Helper

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class DatabaseConnector {
    static {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public static Connection getConnection() {
        Connection connection = null;
        try {
            connection = DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/db_stu", "root", "123456"
            );
        } catch (Exception e) {
            e.printStackTrace();
        }
        return connection;
    }
    
    public static void closeResources(Connection conn, PreparedStatement ps, ResultSet rs) {
        try {
            if (conn != null && !conn.isClosed()) {
                conn.close();
            }
            if (ps != null) {
                ps.close();
            }
            if (rs != null) {
                rs.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

This class manages database connections using MySQL 8.2 JDBC driver.

Defining Entity and Data Access Object

Only the DAO implementation is shown here:

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

public class StudentDAO {
    public List<Student> findAll() {
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        List<Student> students = new ArrayList<>();
        
        try {
            connection = DatabaseConnector.getConnection();
            statement = connection.prepareStatement("SELECT * FROM tb_stu");
            resultSet = statement.executeQuery();
            
            while (resultSet.next()) {
                students.add(new Student(
                    resultSet.getInt(1),
                    resultSet.getString(2),
                    resultSet.getString(3),
                    resultSet.getInt(4)
                ));
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DatabaseConnector.closeResources(connection, statement, resultSet);
        }
        
        return students;
    }
    
    public int deleteById(int studentId) {
        Connection connection = null;
        PreparedStatement statement = null;
        
        try {
            connection = DatabaseConnector.getConnection();
            statement = connection.prepareStatement("DELETE FROM tb_stu WHERE sid = ?");
            statement.setInt(1, studentId);
            return statement.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DatabaseConnector.closeResources(connection, statement, null);
        }
        
        return 0;
    }
    
    public int insert(Student student) {
        Connection connection = null;
        PreparedStatement statement = null;
        
        try {
            connection = DatabaseConnector.getConnection();
            statement = connection.prepareStatement(
                "INSERT INTO tb_stu(sid, sname, ssex, sage) VALUES (?, ?, ?, ?)"
            );
            statement.setInt(1, student.getId());
            statement.setString(2, student.getName());
            statement.setString(3, student.getGender());
            statement.setInt(4, student.getAge());
            return statement.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DatabaseConnector.closeResources(connection, statement, null);
        }
        
        return 0;
    }
}

Exporting Data from MySQL to Excel

Creating Export Implementation

Initialize the workbook and create a sheet to hold data.

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.FileOutputStream;
import java.util.List;

public class ExportToExcel {
    public static void main(String[] args) {
        StudentDAO dao = new StudentDAO();
        
        try (Workbook workbook = new XSSFWorkbook();
             FileOutputStream output = new FileOutputStream("C:\\Users\\fujie\\Desktop\\student_data.xlsx")) {
            
            Sheet sheet = workbook.createSheet("Students");
            List<Student> students = dao.findAll();
            
            Row headerRow = sheet.createRow(0);
            headerRow.createCell(0).setCellValue("ID");
            headerRow.createCell(1).setCellValue("Name");
            headerRow.createCell(2).setCellValue("Gender");
            headerRow.createCell(3).setCellValue("Age");
            
            for (int i = 0; i < students.size(); i++) {
                Student student = students.get(i);
                Row dataRow = sheet.createRow(i + 1);
                dataRow.createCell(0).setCellValue(student.getId());
                dataRow.createCell(1).setCellValue(student.getName());
                dataRow.createCell(2).setCellValue(student.getGender());
                dataRow.createCell(3).setCellValue(student.getAge());
            }
            
            workbook.write(output);
            System.out.println("Data exported successfully");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Importing Data from Excel to MySQL

Creating Import Implementation

Process Excel rows and convert types appropriately.

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.FileInputStream;

public class ImportFromExcel {
    public static void main(String[] args) {
        StudentDAO dao = new StudentDAO();
        
        try (FileInputStream input = new FileInputStream("C:\\Users\\fujie\\Desktop\\student_data.xlsx")) {
            XSSFWorkbook workbook = new XSSFWorkbook(input);
            XSSFSheet sheet = workbook.getSheetAt(0);
            
            for (Row row : sheet) {
                if (row.getRowNum() == 0) continue; // Skip header row
                
                Cell nameCell = row.getCell(1);
                Cell genderCell = row.getCell(2);
                
                if (nameCell != null) {
                    nameCell.setCellType(CellType.STRING);
                }
                
                if (genderCell != null) {
                    genderCell.setCellType(CellType.STRING);
                }
                
                int id = (int) row.getCell(0).getNumericCellValue();
                String name = nameCell.getStringCellValue();
                String gender = genderCell.getStringCellValue();
                int age = (int) row.getCell(3).getNumericCellValue();
                
                Student student = new Student(id, name, gender, age);
                dao.deleteById(id);
                dao.insert(student);
                
                System.out.println("Record inserted successfully");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}