前台提交Form表单数据

form标签的action属性，是将数据提交到的页面。

		<form action="xxxx.jsp" method="post">
    		<p class="main">
    			<label>用户名：</label>
   				<input name="username" value="" /> <br>
   				<label>密码：</label>
   				<input type="password" name="password" value="">
   			</p>
   			<p class="space">
   					<input type="submit" value="提交">
    	</form>

后台判断request请求里的信息。

request.getParameter("username")：对应的请求页面，input标签里name属性
"".equals()：java里这要用双引号
request.getRequestDispatcher("login_success.jsp").forward(request,response);:登录成功，把request和response一起发送至新页面
response.sendRedirect("login_failure.jsp");：登录失败重定向

<%
String path = request.getContextPath();
String username = "";
String password = "";
request.setCharacterEncoding("UTF-8");
username = request.getParameter("username");
password = request.getParameter("password");
if ("admin".equals(username) && "admin".equals(password)){
	session.setAttribute("loginUser", username);
	request.getRequestDispatcher("login_success.jsp").forward(request,response);
} else {
	response.sendRedirect("login_failure.jsp");
}
%>

request.getRequestDispatcher("")和response.sendRedirect("")区别

参照博文：https://www.cnblogs.com/w-wfy/p/6387538.html