jsp中forward动作与param动作

【转载内容】forward动作是指页面跳转至某一页面，而param动作常常和forward动作一起使用，作为其子标签，为页面跳转添加一些参数。

1、forward动作的语法：<jsp:forward page="URL"/>，其中page是指跳转的页面名，forward动作类似于服务器内部转发方法：request.getRequestDispatcher("/url").forward(request, response)

2、param动作的语法：<jsp:param value="参数值" name="参数名"/>，使用param不仅可以新增一个参数，也可以修改原有的参数值。【转载结束】

下面为跟着视频敲的几个例子：

1.首先创建一个登陆页面（login.jsp）,其中form表单提交给forward_action.jsp处理

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>用户登陆界面</title>
</head>
<body>
	<form name="loginForm" action="forward_action.jsp" method="post">
		<table>
			<tr>
				<td>UserName:</td>
				<td><input type="text"  name="username"/></td>
			</tr>
			<tr>
				<td>Password:</td>
				<td><input type="password" name="password"/></td>
			</tr>
			<tr>
				<td colspan="2"><input type="submit" value="登陆"/></td>
			</tr>
		</table>
	</form>
</body>
</html>

2.创建forward_action.jsp，使其跳转到user.jsp(用户资料界面)

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>forward指令 进行跳转</title>
</head>
<body>
	<h1>forward动作</h1>
	<jsp:forward page="user.jsp" />
	<!-- 
		<% request.getRequestDispatcher("user.jsp").forward(request, response); %>
	 -->
</body>
</html>

注意：jsp:forward 动作等价于request.getRequestDispatcher("跳转页面名称").forward(request, response);

【by the way】getRequestDispatcher是服务器内部跳转，地址栏信息不变，只能跳转到web应用内的网页。
sendRedirect是页面重定向，地址栏信息改变，可以跳转到任意网页。

3.user.jsp代码

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登陆成功</title>
</head>
<body>
	<h1>用户资料</h1>
    <hr>
    <% 
       request.setCharacterEncoding("utf-8");
       String username = "";
       String password = "";
       if(request.getParameter("username")!=null)
       {
          username = request.getParameter("username");
       }
       if(request.getParameter("password")!=null)
       {
          password = request.getParameter("password");
       }
    %>
        用户名：<%=username %><br>
        密码：<%=password %><br>
</body>
</html>

【增加param标签】

1.login.jsp中表单提交到dologin.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>用户登陆界面</title>
</head>
<body>
	<form name="loginForm" action="dologin.jsp" method="post">
		<table>
			<tr>
				<td>UserName:</td>
				<td><input type="text"  name="username"/></td>
			</tr>
			<tr>
				<td>Password:</td>
				<td><input type="password" name="password"/></td>
			</tr>
			<tr>
				<td colspan="2"><input type="submit" value="登陆"/></td>
			</tr>
		</table>
	</form>
</body>
</html>

2.dologin.jsp中设置forward动作以及param指定参数值（增加email参数）

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	 <jsp:forward page="user.jsp">
	 	<jsp:param value="Boss" name="username"/>
	 	<jsp:param value="19911007" name="password"/>
	 	<jsp:param value="[email protected]" name="email"/>
	 </jsp:forward>
</body>
</html>

3.user.jsp中输出用户资料

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登陆成功</title>
</head>
<body>
	<h1>用户资料</h1>
    <hr>
    <% 
       request.setCharacterEncoding("utf-8");
       String username = "";
       String password = "";
       String email = "";
       if(request.getParameter("username")!=null)
       {
          username = request.getParameter("username");
       }
       if(request.getParameter("password")!=null)
       {
          password = request.getParameter("password");
       }
       if(request.getParameter("email")!=null)
       {
          email = request.getParameter("email");
       }
       
    %>
        用户名：<%=username %><br>
        密码：<%=password %><br>
        电子邮箱：<%=email %><br>
</body>
</html>

jsp中forward动作与param动作

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