jsp3

---

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

---

<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");

}

%>

---

---

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}