jdbc连接mysql数据库增删改查

import java.sql.*;

public class JDBCDemo {
    // JDBC URL, username and password of MySQL server
    static final String JDBC_URL = "jdbc:mysql://localhost:3306/mydatabase";
    static final String USER = "username";
    static final String PASS = "password";

    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            // 注册JDBC驱动
            Class.forName("com.mysql.cj.jdbc.Driver");

            // 打开连接
            System.out.println("Connecting to database...");
            conn = DriverManager.getConnection(JDBC_URL, USER, PASS);

            // 执行查询
            System.out.println("Creating statement...");
            stmt = conn.createStatement();
            String sql;
            ResultSet rs;

            // 查询数据
            sql = "SELECT id, name, age FROM employees";
            rs = stmt.executeQuery(sql);
            while (rs.next()) {
                // 检索每一行数据
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");

                // 显示数据
                System.out.println("ID: " + id + ", Name: " + name + ", Age: " + age);
            }

            // 插入数据
            sql = "INSERT INTO employees(name, age) VALUES('John Doe', 30)";
            stmt.executeUpdate(sql);
            System.out.println("Inserted records into the table...");

            // 更新数据
            sql = "UPDATE employees SET age = 31 WHERE name = 'John Doe'";
            stmt.executeUpdate(sql);
            System.out.println("Updated records in the table...");

            // 删除数据
            sql = "DELETE FROM employees WHERE name = 'John Doe'";
            stmt.executeUpdate(sql);
            System.out.println("Deleted records from the table...");

        } catch (SQLException se) {
            // 处理JDBC错误
            se.printStackTrace();
        } catch (Exception e) {
            // 处理Class.forName错误
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (stmt != null) stmt.close();
            } catch (SQLException se2) {
            } // 什么都不做
            try {
                if (conn != null) conn.close();
            } catch (SQLException se) {
                se.printStackTrace();
            }
        }
        System.out.println("Goodbye!");
    }
}