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EL与JSTL注意事项汇总
2022-07-05 21:40:00 【全栈程序员站长】
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EL使用表达式(5一个 问题) JSTL使用标签(5问题) 什么是EL。它可以用做? EL全名Expression Language在JSP使用页面 格公式${表达式} 样例${requestScope.customer.id} 功能: 1.才四个域对象中取出属性数据显示
(pageContext.request.session.application)
2.取出请求參数数据显示
<% request.setAttribute(“person”,new Person(“xfzhanag”,18)); %> Map<String,Person> map=new HashMap<String,Person>(); map.put(“A”,new Person(“AA”,12)); map.put(“”B”,new Person(“BB”,13)); map.B.age
{requestScope.person.name}; {requestScope.person[‘name’]}; List里面的第二个数据 <%
<% List list=new ArrayList(); list.add(“a”); list.add(“b”); list.add(“c”); request.setAttribute(“List”,list);
%>
{requestScope.List[1]}; {requestScope.List[‘name’]};
我的年龄:<requestScope.person.name><br/> //什么方便?为什么有个中括号? /* 一种情况? ${requestScope[‘my person’].name}; map.put(“my person”,new Person(“Xxx”,12));
*/ EL能进行的运算? 算数运算(+,-, * ,/ ,%) 关系运算(>,<,==,!=) 逻辑运算(&&,||) empty运算(推断一个数据是否是空) (null,空字符串,空集合)
{empty name}<br>
三目条件运算 {requestScope.person.age>18 ? ‘成年’ : ‘未成年’ }
fmt:formDate SQL标签库 sql http://sun.com/jsp/jstl/sql sql:query xml标签库 xml http://sun.com/jsp/jstl/fmt x:forBach 函数标签库 fn http://sun.com/jsp/jstl/function fn:split 为什么使用JSTL? 在jsp中使用jsp脚本+jsp表达式也能够做循环输出,太麻烦 EL不能做遍历工作 JSTL能做这些并且与jsp和html的标签能够非常好的结合 JSTL高速入门 1.导入JSTL相关的jar包: jstl.jar standard.jar
2.在jsp文件里导入JSTL的c标签库 <%@ taglib uri=”http://java.sun.com/jsp/jstl/core” perfix=”c”
%>
3 <% List<String> list=new ArrayList<String>(); list.add(“A”); list.add(“B”); list.add(“C”); request.setAttribute(“list”,list);
%> <c:forEach items=”
jstl怎样做流程控制? c:if(一重条件推断) c:choose c:when
//需求1:假设我的年龄小于18就输出未成年成(红色字体) <c:if test=”${person.age<18}”> <font color=”red”>未成年人</font> </c:if>
需求2:假设年龄大于60,就输出’老头子‘ 假设年龄小于18,就输出”小屁孩” 其它。就输出”成年人” <br/> <c:choose> <c:when test=”${person.age>60}”>老头子
</c:when> <c:when test=”${person.age<18}”>小屁孩
</c:when> <c:otherwise>成年人</c:otherwise> </c:choose> jstl怎样做遍历? <% Map<String,Person> map=new
HashMap<String,Person>(); map.put(“1”,new Person(“AA”,23)); map.put(“2”,new Person(“BB”,23)); map.put(“3”,new Person(“CC”,23)); map.put(“4”,new Person(“DD”,23)); map.put(“5”,new Person(“EE”,23)); map.put(“6”,new Person(“FF”,23)); request.setAttribute(“personMap”,map); %> <h3>将数据用表格显示出来</h3> <table border=”1″ style=”width:300px”> <tr> <td>ID</td> <td>姓名</td> <td>年龄</td> </tr> <c:forEach items=”{item.key}</td> <td>
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