jsp3

Posted 2020-11-11 maoxiuying

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普通传值：

a1.jsp

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

用户名：<input type="text" name="username" id="username"><br>

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

    <input type="submit">

</form>

a2.jsp

<%

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

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

%>

欢迎<%=username %>

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

用户名：<input type="text" name="username" id="username"><br>

密码:<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")){

    //登录成功

    response.sendRedirect("ok.jsp");

}else{

    //登录失败

    response.sendRedirect("error.jsp");

}

%>

 

在ok.jsp,已经无法取出传给a2.jsp中的username 

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

用户名：<input type="text" name="username" id="username"><br>

密码:<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")){

    //登录成功

    //不影响客户端

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

    //1、把请求转发给ok.jsp,不响应客户端,也不继续处理客户端请求

    //让ok.jsp对客户端进行响应

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

    //问题,地址栏会发生改变吗？

　　不会

    //2、把数据也发一份给ok.jsp

}else{

    //登录失败

    response.sendRedirect("error.jsp");

}

%>

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从页面上获取

<%

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

%>

欢迎<%=username%>

 

 在a2.jsp设置属性

 request.setAttribute("classname", "S145班"); //key(关键字),value

在ok.jsp中获取属性值

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

 

EL表达式

${classname}    //获取属性的值

${param.username}   //从页面上获取参数的值

${param.password}