JSTL标签
一.概述
JSTL(JavaServer Pages Standard Tag Library，即JSP标准标签库)包含了在JSP开发中经常用到的一组标签库，这些标签为我们提供了一种不用嵌入Java代码。就可以开发复杂JSP页面的途径。JSTL标签库的使用是为弥补html标签的不足，规范自定义标签的使用而诞生的。使用JSLT标签的目的就是不希望在JSP页面中出现Java逻辑代码。 JSTL是由SUN公司推出的，由Apache Jakarta组织负责维护的用于编写和开发JSP页面的一组标准标签。作为开源的标准技术，它一直在不断的完善。JSTL标签库包含了各种标签，如通用标签、条件判断标签和迭代标签等。
二.标签使用
在工程中引用JSTL的jar包 对1.1版本的JSTL在工程中进行引用，添加jstl.jar和standard.jar两个包，放置到项目的WebRoot/WEB-INF/lib目录下即可。在MyEclipse集成开发环境中已经集成了JSTL，这个过程可以有工具代为实现。 在需要JSTL的JSP页面使用taglib指令导入标签库描述文件 如果需要使用JSTL核心标签库，在页面上方增加如下一行指令：<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> 如果需要添加SQL标签库、格式标签库、XML标签库和函数标签库，添加的指令如下。例如添加SQL标签库指令：<%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> 核心标签库 <%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %> sql标签库 <%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %> 格式标签库 <%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %> xml标签库 <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %> 函数标签库
三.JSTL核心标签库
通用标签库:(1) <c:set>标签 (2) <c:out>标签 (3) <c:remove>标签
条件标签库:(1) <c:if>标签 (2) <c:choose>标签
迭代标签库:(1) <c:forEach>标签 (2) <c:forTokens>标签
通用标签库
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
</head>
<body>
设置变量之前的message值：
<c:out value="${message}" default="null"></c:out>
<br>
<c:set var="message" value="helloword!" scope="page"></c:set>
设置新值之后的message值：
<br>
<c:out value="${message}"></c:out><br>
<c:remove var="message" scope="page"></c:remove>
<br>
移除变量后message的值：
<c:out value="${message}"default="null"></c:out>
</body>
</html>条件标签库
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>JSTL条件标签库的使用</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<c:set var="isLogin" value="${not empty sessionScope.LOGIN_NAME }"></c:set>
<c:if test="${not isLogin }">
<form name="form1" method="post" action="doJstlCondition.jsp">
用户名：<input type="text" name="username"> <br>
密 码：<input type="password" name="password"> <br>
<input type="submit" value="登录">
</form>
</c:if>
<c:if test="${isLogin }">
<c:out value="${sessionScope.LOGIN_NAME } "></c:out>已经登录！
</c:if>
<c:choose>
<c:when test="${row.v_money<10000 }">
初级者
</c:when>
<c:when test="${row.v_money>=10000 && row.v_money<20000}">
中级者
</c:when>
<c:otherwise>
高级者
</c:otherwise>
</c:choose>
</body>
</html>
doJstlCondition.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'doJstlCondition.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<%
request.setCharacterEncoding("utf-8");
String username=request.getParameter("username");
String password=request.getParameter("password");
if(username.equals("admin") && password.equals("123")){
session.setAttribute("LOGIN_NAME", username);
response.sendRedirect("jstlCondition.jsp");
}else{
out.println("用户名或者密码错误!");
}
%>
</body>
</html>
迭代标签库:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page import="com.chinasofti.entity.Admin" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%
Admin admin=null;
List adminList=new ArrayList();
for(int i=0;i<10;i++){
admin=new Admin(i+1,"管理员"+(i+1),"密码"+(i+1));
adminList.add(admin);
}
request.setAttribute("ADMINLIST", adminList);
%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>JSTL迭代标签的使用</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<table border="1" width="70%" align="center">
<tr>
<td>ID</td>
<td>用户名</td>
<td>密码</td>
</tr>
<c:forEach var="admin" items="${requestScope.ADMINLIST}" varStatus="status">
<tr <c:if test="${status.index%2==1}">style="background-color:yellow;" </c:if>>
<td>${admin.id }</td>
<td>${admin["loginName"] }</td>
<td>${admin.loginPwd }</td>
</tr>
</c:forEach>
</table>
<br>
<c:forTokens items="China,Russia,France" delims="," var="item">
<c:out value="${item }"/> <br>
</c:forTokens>
</body>
</html>
