JSTL标签库
JSTL标准标签库；
JSTL用于简化JSP开发，提高代码的可读性与可维护性；
JSTL由SUN(Oracle)定义规范，由Apache Tomcat团队实现；
引用JSTL核心库
- 核心标签库(Core)是JSTL最重要的标签库，提供了JSTL的基础功能
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>- JSTL核心标签库在taglibs-standard-impl.jar由META-INF/c.tld定义
条件判断
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
<%
int x = 15;
request.setAttribute("x", x);
%>
<c:if test="${ requestScope.x > 0 && requestScope.x <= 10 }">
<div style="color:blue;font-weight:bold;">1-10之间的整数</div>
</c:if>
<c:if test="${ requestScope.x > 10 && requestScope.x <= 20 }">
<div style="color:red;font-weight:bold;">11-20之间的整数</div>
</c:if>
</body>
</html>
多重条件判断
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
<c:choose>
<c:when test="${ param.day == 'MONDAY' }">
<h2 style="color:blue;">星期一</h2>
</c:when>
<c:when test="${ param.day == 'TUESDAY' }">
<h2 style="color:blue;">星期二</h2>
</c:when>
<c:when test="${ param.day == 'WEDNESDAY' }">
<h2 style="color:blue;">星期三</h2>
</c:when>
<c:when test="${ param.day == 'THURSDAY' }">
<h2 style="color:blue;">星期四</h2>
</c:when>
<c:when test="${ param.day == 'FRIDAY' }">
<h2 style="color:blue;">星期五</h2>
</c:when>
<c:when test="${ param.day == 'SATURDAY' }">
<h2 style="color:blue;">星期六</h2>
</c:when>
<c:when test="${ param.day == 'SUNDAY' }">
<h2 style="color:blue;">星期日</h2>
</c:when>
<c:otherwise>
<h2 style="color:red;">内容不对哦！</h2>
</c:otherwise>
</c:choose>
</body>
</html>
遍历循环
MonthServlet.java
package jstl;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class MonthServlet
*/
@WebServlet("/month")
public class MonthServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public MonthServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Set<String> setMonths = new HashSet();
setMonths.add("January");
setMonths.add("February");
setMonths.add("March");
setMonths.add("April");
setMonths.add("May");
request.setAttribute("months", setMonths);
request.getRequestDispatcher("/month.jsp").forward(request, response);
}
}
month.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<c:forEach items="${requestScope.months }" var="c" varStatus="idx">
<h2>${idx.index + 1} —— ${c }</h2>
</c:forEach>
</body>
</html>
c:out
- 属于核心标签库(Core)
<c:out value="${nothing}" default="无"></c:out>(nothing=null)将原本为null的值转义为"无"<c:out value="${html}" escapeXml="true"></c:out>浏览器不进行解释，将html源代码显示
fmt格式化标签库
- fmt格式化标签库URI:
http://java.sun.com/jsp/jstl/fmt <fmt:formatDate value="" pattern="">格式化日期标签<fmt:formatNumber value="" pattern="">格式化数字标签
formatDate pattern
| yyyy | 四位年 | | ---- | -------- | | MM | 两位月 | | dd | 两位日 | | HH | 24小时制 | | hh | 12小时制 | | mm | 分钟 | | ss | 秒数 | | SSS | 毫秒 |formatNumber pattern
- "0.00"：保留两位小数
- "0,000.00"：三位一分隔，保留两位小数