【JSTL】--JSTL表达式:c:set,c:if,c:choose,--drp214
jstl_core.jsp
<%@ page language="java" contentType="text/html; charset=GB18030" pageEncoding="GB18030"%> <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> <!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=GB18030"> <title>Insert title here</title> </head> <body> <h1>测试JSTL核心库</h1> <hr> <li>采用c:out标签</li><br> hello(使用标签:)<c:out value="123"/><br> hello(使用标签:)<c:out value="hello"/><br> hello(使用标签:)<c:out value="${hello}"/><br> hello(使用标签:EL表达式)${hello}<br> hello(default):${hello123 }<br> hello(使用缺省值):<c:out value="${hello123 }" default="没有值"/><br> hello(使用缺省值):<c:out value="${hello123 }" >没有值</c:out><br> Welcome(使用EL表达式):${welcome}<br> welcome(使用标签,escapeXml=true):<c:out value="${welcome }" escapeXml="true"/><br> welcome(使用标签,escapeXml=false):<c:out value="${welcome }" escapeXml="false"/><br> <p> <li>测试 c:set ,c:remove</li><br> <c:set value="root" var="userid"/> userid:${userid}<br> <c:remove var="userid"/> userid:${userid }<br> <p> <li>条件控制标签c:if</li><br> <c:if test="${v1 lt v2 }"> v1小于v2 </c:if> <p> <li>条件控制标签:c:choose,c:when,c:otherwise</li><br> <c:choose> <c:when test="${v1 gt v2 }"> v1大于v2<br> </c:when> <c:otherwise> v1小于v2<br> </c:otherwise> </c:choose> <c:choose> <c:when test="${empty userList }"> 没有符合条件的数据<br> </c:when> <c:otherwise> 存在用户数据<br> </c:otherwise> </c:choose> </body> </html>
JstlCoreServlet:
/** * */ package com.bjpowrnode.jstl; import java.io.IOException; import java.util.ArrayList; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @ClassName:JstlCoreServlet * @Description:TODO * @author wm * @date 2016年2月15日上午11:40:32 */ public class JstlCoreServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //普通字符串 request.setAttribute("hello","Hello World!"); request.setAttribute("welcome", "<font color='red'>欢迎你来到这个世界!</font>"); //条件控制标签、 request.setAttribute("v1", 10); request.setAttribute("v2", 20); request.setAttribute("userList", new ArrayList()); request.getRequestDispatcher("/jstl_core.jsp").forward(request, response); } }