客戶 image col alt 問題 direct str strong tro

---

普通傳值：

a1.jsp

<form action="a2.jsp" method="post">

用戶名：<input type="text" name="username" id="username"><br>

密碼:<input type="password" name="password"><br>

<input type="submit">

</form>

a2.jsp

<%

String username = request.getParameter("username");

String password = request.getParameter("username");

%>

歡迎<%=username %>

<form action="a2.jsp" method="post">

用戶名：<input type="text" name="username" id="username"><br>

密碼:<input type="password" name="password"><br>

<input type="submit">

</form>

String username = request.getParameter("username");

String password = request.getParameter("password");

if (username.equals("admin")&&password.equals("123456")){

//登錄成功

response.sendRedirect("ok.jsp");

}else{

//登錄失敗

response.sendRedirect("error.jsp");

}

%>

在ok.jsp,已經無法取出傳給a2.jsp中的username

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<form action="a2.jsp" method="post">

用戶名：<input type="text" name="username" id="username"><br>

密碼:<input type="password" name="password"><br>

<input type="submit">

</form>

---

<%

String username = request.getParameter("username");

String password = request.getParameter("password");

if (username.equals("admin")&&password.equals("123456")){

//登錄成功

//不影響客戶端

//response.sendRedirect("ok.jsp");

//1、把請求轉發給ok.jsp,不響應客戶端,也不繼續處理客戶端請求

//讓ok.jsp對客戶端進行響應

request.getRequestDispatcher("ok.jsp").forward(request, response);

//問題,地址欄會發生改變嗎？

　　不會

//2、把數據也發一份給ok.jsp

}else{

//登錄失敗

response.sendRedirect("error.jsp");

}

%>

---

---

從頁面上獲取

<%

String username = request.getParameter("username");

%>

歡迎<%=username%>

在a2.jsp設置屬性

request.setAttribute("classname", "S145班"); //key(關鍵字),value

在ok.jsp中獲取屬性值

<%
String classname = request.getAttribute("classname").toString();
%>
<%=classname %>

EL表達式

${classname} //獲取屬性的值

${param.username} //從頁面上獲取參數的值

${param.password}

jsp3