從零搭建 Java Web 開發環境：Eclipse + Tomcat + Servlet + Oracle 完整教學

建立 Dynamic Web Project

1. File → New → Dynamic Web Project
2. Project name: ServletOracleDemo
3. Target runtime: 選擇剛新增的 Tomcat
4. Dynamic web module version: 6.0 (Tomcat 10) / 4.0 (Tomcat 9)
5. Configuration: Default → Finish

建立 Servlet

1. 右鍵 src → New → Servlet
2. Package: com.example.servlet
3. Class name: EmployeeServlet
4. URL mapping: /employees (自動生成 @WebServlet("/employees"))
5. Finish

導入 Oracle JDBC 驅動

方式一：Maven 專案 (推薦)

<dependency>
    <groupId>com.oracle.database.jdbc</groupId>
    <artifactId>ojdbc11</artifactId>
    <version>23.4.0.0</version>
</dependency>

方式二：手動加入 Build Path

1. 專案右鍵 → Build Path → Configure Build Path
2. Libraries → Classpath → Add External JARs
3. 選擇 ojdbc11.jar → Apply and Close

Oracle 連線與查詢 Servlet 完整代碼

@WebServlet("/employees")
public class EmployeeServlet extends HttpServlet {
    private static final String URL = "jdbc:oracle:thin:@localhost:1521:ORCL";
    private static final String USER = "SCOTT";
    private static final String PASS = "tiger";

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        resp.setContentType("text/html;charset=UTF-8");
        try (PrintWriter out = resp.getWriter();
             Connection conn = DriverManager.getConnection(URL, USER, PASS);
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("SELECT ename, job, sal FROM emp")) {

            out.println("");
            out.println("");
            out.println("
員工資料 (SCOTT.EMP)
");
            out.println("");

            while (rs.next()) {
                out.printf("%n",
                    rs.getString("ename"),
                    rs.getString("job"),
                    rs.getInt("sal"));
            }
            out.println("
姓名
職稱
薪資
%s
%s
%,d
");

        } catch (SQLException e) {
            throw new ServletException("資料庫查詢失敗", e);
        }
    }
}

執行與驗證

1. 專案右鍵 → Run As → Run on Server
2. 選擇 Tomcat → Finish
3. 瀏覽器開啟 https://localhost:8080/ServletOracleDemo/employees
4. 應顯示 EMP 表格資料

常見問題排查

進階建議

• 連線池：生產環境必須使用 HikariCP/Druid，配置 JNDI DataSource
• DAO 模式：分離資料存取邏輯，Servlet 僅處理 HTTP 協議
• 參數化查詢：使用 PreparedStatement 防 SQL 注入
• 異常處理：統一錯誤頁面，記錄日誌不暴露堆疊給用戶
• 建構工具：新專案優先選 Maven/Gradle，依賴管理與 CI/CD 友善