用Servlet即把jdbc那套放到繼承於HttpServlet的派生類之內，那段程式碼很簡單

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {       
        response.setCharacterEncoding("Unicode");        
        PrintWriter out=response.getWriter();
        String name
 
=request.getParameter("username");
        String passwd=request.getParameter("passwd");        
      try {
        Class.forName("com.mysql.jdbc.Driver");
    //    Class.forName("com.mysql.cj.jdbc.Driver");
        Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/stu", "root", "root");
        
 
//Statement stmt=conn.createStatement();
        //ResultSet rs=stmt.executeQuery(sql);  //查詢    
        java.sql.PreparedStatement pstmt=conn.prepareStatement("select * from tb_user where name=? and password=?");
        pstmt.setString(1, name);
        pstmt.setString(2, passwd);
        //System.out.println();
 

        ResultSet rs=pstmt.executeQuery();
        rs.beforeFirst();
        if(rs.next())
        {
            out.println(rs.getString(1)+":"+rs.getString(2));
        }
        else{
            out.println("不存在該使用者!");
        }        
        rs.close();
        conn.close();
    } catch (ClassNotFoundException | SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }            
    }

  但注意要把jdbc放到tomcat目錄中的lib中，不然報的那種錯誤，確實有點讓人看不懂

  還有編碼的格式需要注意一下，有時候Mysql資料表中的編碼，會與介面的編碼格式不一致，比如我這是Unicode的

    response.setCharacterEncoding("Unicode");  

 把Web.xml的配置檔案也放上吧

  <servlet>
    <servlet-name>Login</servlet-name>
    <servlet-class>com.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Login</servlet-name>
    <url-pattern>/ServerCoding1/aaa</url-pattern>
  </servlet-mapping>

呼叫類似

<a href="aaa">跳轉<a/>

或

   
   <form action="ServerCoding1/aaa" method="post">

   <input type="submit" value="跳轉">
     </form>