el函数标记库的使用

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%> <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> <%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%> <%@ taglib uri="/WEB-INF/el-function.tld" prefix="f"%> <jsp:useBean id="list" class="java.util.ArrayList"></jsp:useBean> ${f:len(list) gt 0} <jsp:useBean id="date" class="java.util.Date"></jsp:useBean> <fmt:formatDate var="date" value="${date}" pattern="yyyy年M月" /> ${date} <fmt:formatNumber var="price" value="100" pattern="￥0.00" /> ${price}
<?xml version="1.0" encoding="GB18030"?> <taglib version="2.0" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd"> <tlib-version>1.0</tlib-version> <short-name>el-funciton</short-name> <function> <name>len</name> <function-class>el.ELFunction</function-class> <function-signature> java.lang.Integer length(java.lang.Object) </function-signature> </function> </taglib>
package el; import java.util.Collection; import java.util.Map; public class ELFunction { public static Integer length(Object object) { if (object instanceof Collection) { return ((Collection) object).size(); } else if (object instanceof Map) { return ((Map) object).size(); } else if (object instanceof Object[]) { return ((Object[]) object).length; } return 0; } }