java自定义JDBC实现连接池

import java.sql.*;

public class Main {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/your_database_name";
        String username = "your_username";
        String password = "your_password";

        Connection connection = null;
        try {
            connection = DriverManager.getConnection(url, username, password);
            System.out.println("成功连接到数据库");

            // 查询操作
            String query = "SELECT * FROM your_table_name";
            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(query);

            // 打印查询结果
            while (resultSet.next()) {
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                System.out.println("ID: " + id + ", Name: " + name);
            }

            // 更新操作
            String update = "UPDATE your_table_name SET name = 'New Name' WHERE id = 1";
            int rowsAffected = statement.executeUpdate(update);
            System.out.println("更新操作影响的行数: " + rowsAffected);

        } catch (SQLException e) {
            System.out.println("数据库操作失败：" + e.getMessage());
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                    System.out.println("成功关闭数据库连接");
                } catch (SQLException e) {
                    System.out.println("关闭数据库连接失败：" + e.getMessage());
                }
            }
        }
    }
}

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

public class ConnectionPool {
    private static final int MAX_CONNECTIONS = 10; // 最大连接数限制
    private static final long CONNECTION_TIMEOUT = 5000; // 连接超时时间，单位毫秒

    private Vector<Connection> availableConnections = new Vector<>();
    private Vector<Connection> usedConnections = new Vector<>();

    public ConnectionPool(String url, String username, String password) {
        initializeConnectionPool(url, username, password);
    }

    private void initializeConnectionPool(String url, String username, String password) {
        while (!checkIfConnectionPoolIsFull()) {
            availableConnections.add(createNewConnection(url, username, password));
        }
        System.out.println("数据库连接池初始化完成，当前连接数: " + availableConnections.size());
    }

    private synchronized boolean checkIfConnectionPoolIsFull() {
        return (availableConnections.size() + usedConnections.size()) >= MAX_CONNECTIONS;
    }

    private Connection createNewConnection(String url, String username, String password) {
        try {
            return DriverManager.getConnection(url, username, password);
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }
    }

    public synchronized Connection getConnection() throws SQLException {
        long startTime = System.currentTimeMillis();
        while (availableConnections.isEmpty()) {
            try {
                wait(CONNECTION_TIMEOUT);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            if ((System.currentTimeMillis() - startTime) >= CONNECTION_TIMEOUT) {
                throw new SQLException("获取数据库连接超时");
            }
        }

        Connection connection = availableConnections.remove(availableConnections.size() - 1);
        usedConnections.add(connection);
        System.out.println("获取数据库连接，当前连接数: " + availableConnections.size());
        return connection;
    }

    public synchronized void releaseConnection(Connection connection) {
        if (connection != null) {
            usedConnections.remove(connection);
            availableConnections.add(connection);
            notifyAll();
            System.out.println("释放数据库连接，当前连接数: " + availableConnections.size());
        }
    }
}

public class ConnectionPoolTest {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/your_database_name";
        String username = "your_username";
        String password = "your_password";

        ConnectionPool connectionPool = new ConnectionPool(url, username, password);

        // 模拟多个线程同时请求数据库连接
        for (int i = 0; i < 15; i++) {
            Thread thread = new Thread(new Worker(connectionPool, i));
            thread.start();
        }
    }

    static class Worker implements Runnable {
        private ConnectionPool connectionPool;
        private int workerId;

        public Worker(ConnectionPool connectionPool, int workerId) {
            this.connectionPool = connectionPool;
            this.workerId = workerId;
        }

        @Override
        public void run() {
            try (Connection connection = connectionPool.getConnection()) {
                System.out.println("Worker " + workerId + " 获取到数据库连接");
                // 模拟操作持有连接的时间
                Thread.sleep(3000);
                System.out.println("Worker " + workerId + " 完成操作，释放数据库连接");
            } catch (SQLException | InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

import java.sql.*;

public class Main {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/your_database_name";
        String username = "your_username";
        String password = "your_password";

        Connection connection = null;
        try {
            connection = DriverManager.getConnection(url, username, password);
            // 执行数据库操作...
        } catch (SQLException e) {
            System.out.println("数据库操作失败：" + e.getMessage());
            e.printStackTrace();
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    System.out.println("关闭数据库连接失败：" + e.getMessage());
                    e.printStackTrace();
                }
            }
        }
    }
}