JSTL tag libraries
JSTL standard tag library;
JSTL JSP to simplify development, improve the readability and maintainability of the code;
JSTL, implemented by SUN (Oracle) specification defined by the Apache Tomcat team;
JSTL core library reference
- The core tag library (Core) is the most important JSTL tag libraries, JSTL provides basic functionality
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>- JSTL core tag library in taglibs-standard-impl.jar defined by META-INF / c.tld
Conditional
<%@ 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>Multiple conditional
<%@ 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="${ param.day == 'SUNDAY' }">
<h2 style="color:blue;">星期日</h2>
</c:when>
<c:otherwise>
<h2 style="color:red;">内容不对哦！</h2>
</c:otherwise>
</c:choose>
</body>
</html>Traversal cycle
MonthServlet.java
package jstl;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class MonthServlet
*/
@WebServlet("/month")
public class MonthServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public MonthServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Set<String> setMonths = new HashSet();
setMonths.add("January");
setMonths.add("February");
setMonths.add("March");
setMonths.add("April");
setMonths.add("May");
request.setAttribute("months", setMonths);
request.getRequestDispatcher("/month.jsp").forward(request, response);
}
}month.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<c:forEach items="${requestScope.months }" var="c" varStatus="idx">
<h2>${idx.index + 1} —— ${c }</h2>
</c:forEach>
</body>
</html>c:out
- Belong to the core tag library (Core)
<c:out value="${nothing}" default="无"></c:out>(Nothing = null) originally escaped as "no" null value<c:out value="${html}" escapeXml="true"></c:out>Browser does not interpret the html source code display
fmt formatting tag library
- fmt formatting tag library URI:
http://java.sun.com/jsp/jstl/fmt <fmt:formatDate value="" pattern="">Date Format Label<fmt:formatNumber value="" pattern="">Format digital label
formatDate pattern
| yyyy | Four years |
|---|---|
| MM | Two months |
| dd | Two days |
| HH | 24-hour clock |
| hh | 12-hour |
| mm | minute |
| ss | The number of seconds |
| SSS | millisecond |
formatNumber pattern
- "0.00": two decimal places
- "0,000.00": a three separate, two decimal places