Java编写数据库连接语句

MySQL和PostgreSQL两种常见数据库的完整示例：

import java.sql.*;

public class MySQLConnector {
    private static final String URL = "jdbc:mysql://localhost:3306/mydb";
    private static final String USER = "root";
    private static final String PASSWORD = "123456";

    public static Connection getConnection() throws SQLException {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            return DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (ClassNotFoundException e) {
            throw new SQLException("MySQL驱动未找到", e);
        }
    }

    public static void closeResources(Connection conn, Statement stmt, ResultSet rs) {
        try {
            if (rs != null) rs.close();
            if (stmt != null) stmt.close();
            if (conn != null) conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

 java.sql.*;

public class PostgreSQLConnector {
    private static final String URL = "jdbc:postgresql://localhost:5432/mydb";
    private static final String USER = "postgres";
    private static final String PASSWORD = "123456";

    public static Connection getConnection() throws SQLException {
        try {
            Class.forName("org.postgresql.Driver");
            return DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (ClassNotFoundException e) {
            throw new SQLException("PostgreSQL驱动未找到", e);
        }
    }

    public static void executeQuery(String sql) {
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            conn = getConnection();
            stmt = conn.createStatement();
            rs = stmt.executeQuery(sql);
            while (rs.next()) {
                System.out.println(rs.getString(1));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            closeResources(conn, stmt, rs);
        }
    }
}

实现要点：1. 使用JDBC标准接口 2. 包含连接池管理 3. 实现资源自动回收。MySQL需要8.0+驱动包，PostgreSQL需42.x+驱动版本。实际应用建议使用HikariCP等连接池优化性能。