JavaWeb学习心得之JSP标签

时间：2021-08-29 13:36:59

一、JSP标签概念

       JSP标签也称之为Jsp Action元素，它用于在JSP页面中提供业务逻辑功能，避免直接写Java代码。


二、常用JSP标签

常用标签：

  •  <jsp：include>
  • <jsp：forward>
  • <jsp：param>
1.<jsp：include>标签
作用：用于把另外一个资源的内容插入当前JSP页面的内容中，这种JSP在执行时的引入方式称为动态引入。
语法：<jsp:include page="url" flush="true" />,其中page属性指定被引入资源的路径，flush是否刷新当前JSP页面已输出的内容。

引入资源：
JavaWeb学习心得之JSP标签
<jsp:include>标签和include指令的区别
head.jsp文件 
<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html lang="en">


<!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT -->
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

    <title>test</title>
</head>

<body>
	<%
		int i=1000;
	%>
	<!-- 用jsp标签引入资源内容 -->
	<p>head页面中i的值为<%=i %></p>
</body>
</html>

include指令是静态引入 
<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html lang="en">


<!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT -->
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

    <title>test</title>
</head>

<body>
	<%
		int i=100;
	%>
	<!-- 用jsp标签引入资源内容 -->
	<p>test页面中i的值为<%=i %></p>
	<%@include file="/head.jsp" %>
</body>
</html>
访问结果：便宜错误
JavaWeb学习心得之JSP标签
 
      以上结果，是因为include指令是先引入在处理，当head.jsp引入后，head.jsp和test.jsp中同时存在相同的变量i，所以有冲突，导致编译异常。

<jsp:include>动态引入 
	<%@ page language="java" contentType="text/html; charset=UTF-8"
		pageEncoding="UTF-8"%>
	<!DOCTYPE html>
	<html lang="en">


	<!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT -->
	<head>
	    <meta charset="utf-8">
	    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

	    <title>test</title>
	</head>

	<body>
		<%
			int i=100;
		%>
		<!-- 用jsp标签引入资源内容 -->
		<p>test页面中i的值为<%=i %></p>
		<jsp:include page="/head.jsp"></jsp:include>
	</body>
	</html>

访问结果
JavaWeb学习心得之JSP标签
       <jsp:include>动态引入，是先处理两个JSP页面，然后再引入内容。

2.<jsp:forward>标签
作用：用于把请求转发给另外一个资源。
语法：<jsp:forward page="url"/> page属性用于指定请求转发资源路径
示例
test.jsp 
	<%@ page language="java" contentType="text/html; charset=UTF-8"
		pageEncoding="UTF-8"%>
	<!DOCTYPE html>
	<html lang="en">


	<!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT -->
	<head>
	    <meta charset="utf-8">
	    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

	    <title>test</title>
	</head>

	<body>
		<!-- 用jsp标签转发 -->
		<jsp:forward page="/test1.jsp"></jsp:forward>
	</body>
	</html>
test1.jsp 
<%@ page language="java" contentType="text/html; charset=UTF-8"	pageEncoding="UTF-8"%><!DOCTYPE html><html lang="en"><!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT --><head>    <meta charset="utf-8">    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">    <title>test</title></head><body>	<p>转发后的页面</p></body></html>
访问结果：
JavaWeb学习心得之JSP标签

3.<jsp:param>标签
作用：当使用<jsp:include>和<jsp:forward>标签引入或将请求转发给其它资源时，可以使用<jsp:param>标签向这个资源传递参数。
语法：
  • <jsp:include page="url"><jsp:param name="" value="" /></jsp:include>
  • <jsp:forward page="url"><jsp:param name="" value="" /></jsp:forward>
       其中，name属性指定参数名，value属性指定参数值

示例1：
test.jsp 
	<%@ page language="java" contentType="text/html; charset=UTF-8"
		pageEncoding="UTF-8"%>
	<!DOCTYPE html>
	<html lang="en">


	<!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT -->
	<head>
	    <meta charset="utf-8">
	    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

	    <title>test</title>
	</head>

	<body>
		<!-- 用jsp标签转发 -->
		<jsp:forward page="/test1.jsp">
			<jsp:param value="hello" name="param1"/>
			<jsp:param value="world" name="param2"/>
		</jsp:forward>
	</body>
	</html>

test1.jsp 
<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html lang="en">


<!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT -->
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

    <title>test</title>
</head>

<body>
	<p>接收到的参数</p>
	<p><%=request.getParameter("param1") %></p>
	<p><%=request.getParameter("param2") %></p>
</body>
</html>

JavaWeb学习心得之JSP标签

示例2
test.jsp 
	<%@ page language="java" contentType="text/html; charset=UTF-8"
		pageEncoding="UTF-8"%>
	<!DOCTYPE html>
	<html lang="en">


	<!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT -->
	<head>
	    <meta charset="utf-8">
	    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

	    <title>test</title>
	</head>

	<body>
		<jsp:include page="/head.jsp">
			<jsp:param value="hello" name="param1"/>
			<jsp:param value="world" name="param2"/>
		</jsp:include>
	</body>
	</html>

test1.jsp 
<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html lang="en">


<!-- Mirrored from www.zi-han.net/theme/hplus/login_v2.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 20 Jan 2016 14:19:49 GMT -->
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

    <title>test</title>
</head>

<body>
	<p>接收到的参数</p>
	<p><%=request.getParameter("param1") %></p>
	<p><%=request.getParameter("param2") %></p>
</body>
</html>

访问结果：
JavaWeb学习心得之JSP标签




标签：

相关文章