JDBC 連線 DB2、Oracle、MySQL、PostgreSQL 通用範本

完整 Java 範例程式

package com.terac.util;

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

public class DBTest {
    public static void main(String[] args) {
        try {
            // 通用連線參數
            String user = "user";
            String password = "passWord";

            // --- DB2 ---
            String driver = "com.ibm.db2.jcc.DB2Driver";  // 新版通用驅動
            String url = "jdbc:db2://localhost:50000/sample";
            String sql = "SELECT CURRENT TIMESTAMP FROM SYSIBM.SYSDUMMY1";

            /* --- Oracle ---
            String driver = "oracle.jdbc.OracleDriver";
            String url = "jdbc:oracle:thin:@localhost:1521:ORCL";
            String sql = "SELECT SYSDATE FROM DUAL";
            */

            /* --- MySQL ---
            String driver = "com.mysql.cj.jdbc.Driver";
            String url = "jdbc:mysql://localhost:3306/test?serverTimezone=UTC";
            String sql = "SELECT NOW()";
            */

            /* --- PostgreSQL ---
            String driver = "org.postgresql.Driver";
            String url = "jdbc:postgresql://localhost:5432/test";
            String sql = "SELECT CURRENT_TIMESTAMP";
            */

            Class.forName(driver).newInstance();
            Connection conn = DriverManager.getConnection(url, user, password);
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery(sql);

            while (rs.next()) {
                System.out.println(rs.getString(1));
            }

            rs.close();
            stmt.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

關鍵差異對照表

注意事項

• DB2 舊驅動 COM.ibm.db2.jdbc.Net.DB2Driver 已棄用，請改用 JCC 通用驅動。
• MySQL 8.0+ 需加 serverTimezone 參數避免時區警告。
• 生產環境請使用連線池 (HikariCP/Druid) 並外部化配置。
• 查詢單一值可用 prepareStatement + executeQuery，防止注入。