• out 标签

    value:输出值，default:默认输出值，escape:特殊字符是否转义
    <c:out value="<Hello World!>" default="defalut" escapeXml="false">
    HtmlUtils.htmlUnescape(help); -> 富文本不转义(Spring)

• redirect 标签

        <c:url var="url" value="index.jsp">
            <c:param name="name" value="wjx"/>
            <c:param name="pass" value="xjw"/>
        </c:url>
        <c:redirect url="${url}"/>

• set 标签

    <c:set value="wjx" var="wjx" scope="request"></c:set> -> 方式一
    <jsp:useBean id="person" class="bean.Person"/> -> 方式二
    <c:set target="${person}" property="name" value="123"/> -> 赋值

• remove 标签

    <c:remove var="wjx" scope="request"/> -> 请求域移除参数

• if 标签

    结果为True，执行标签体
    <c:if test="${not empty tag}">
         <c:if test="${tag eq 'new'}">
                <i onclick="window.location.href='${url}'">new</i>
         </c:if>
    </c:if>

• case 标签

    <%--大写转换小写--%>
    ${fn:toLowerCase("ITCAST")}<br>
    <%--小写转换大写--%>
    ${fn:toUpperCase("wjx")}

• fn:contains 标签

    <%--区别大小写--%>
    ${fn:contains("wjx","w")};<br>
    ${fn:contains("wjx","W")};<br>
    <%--不区别大小写--%>
    ${fn:containsIgnoreCase("wjx","w" )};<br>
    ${fn:containsIgnoreCase("wjx","W" )};<br>

• fn:escapeXml 标签

    ${fn:escapeXml("<br>")}<br>
    <c:out value="<br>" escapeXml="true" default="转义"></c:out><br>
    ${"<b>我</b>"}

• fn:indexOf 标签

    ${fn:indexOf("wjx","w" )}<br>
    ${fn:indexOf("wjx","j" )}<br>
    ${fn:indexOf("wjx","x" )}<br>

• fn:join 标签

    <%  String strs[]={"www","itcast","com"};  %>
    <c:set var="strs" value="<%=strs%>"/>
    ${fn:join(strs,".")}

• fn:length 标签

    <%
    int[] array={1,2,3,4};
    List list = new ArrayList();
    list.add("one");
    list.add("two");
    list.add("three");
    %>

    <c:set value="<%=array%>" var="array"/>
    <s:set value="<%=list%>" var="list"/>
    数组长度:${fn:length(array)}<br>
    集合长度:${fn:length(list)}<br>
    字符串长度:${fn:length("Tomcat")}<br>

• fn:replace 标签

    <%--字符串替换--%>
    ${fn:replace("w.j.x","." ,"" )}

• fn:split 标签

    <c:set var="strs" value='${fn:split("w j x"," ")}'/>
    <c:forEach var="each" items="${strs}" >
        <c:out value="${each}" escapeXml="true" default="sss"/><br>
    </c:forEach>

• fn:substring 标签

    <%--字符串抽取--%>
    ${fn:substring("wjx",0 ,2 )}<br>
    ${fn:substringBefore("wjx", "j")}<br>
    ${fn:substringAfter("wjx","j" )}

• fn:trim 标签

    <%--清除字符串前后的空格--%>
    ${fn:trim("wjx")}

• fn:startsWith 标签 、fn:endsWith 标签

    <%--开头--%>
    ${fn:startsWith("wjx","w")}<br>
    ${fn:startsWith("wjx","j")}<br>
    <%--结束--%>
    ${fn:endsWith("wjx","x" )}<br>
    ${fn:endsWith("wjx","j" )}<br>

• catch 标签

    <c:catch var="wjx">
        <%
        int j=10;
        int i=0;
        System.out.println(j/i);
        %>
    </c:catch>

• choose 标签

    <c:choose>
        <c:when test="${empty param.username}">
            param没有参数
        </c:when>
        
        <c:when test="${param.username=='wjx'}">
            wjx
        </c:when>

        <c:otherwise>
            else
        </c:otherwise>
    </c:choose>

• forEach 标签

<%--数组--%>
<%
    String[] fruits = {"apple", "orange", "grape", "banana"};
%>
<c:forEach var="wjx" items="<%=fruits%>">
    ${wjx}<br>
</c:forEach>

<%--Map集合--%>
<%
    Map map = new HashMap();
    map.put("Tom", "123");
    map.put("Mike", "123");
    map.put("Lina", "123");
%>
<c:forEach var="map" items="<%=map%>">
    ${map.key}&nbsp; ${map.value}<br>
</c:forEach>

<%--List集合--%>
<%
    List list = new ArrayList();
    list.add("red");
    list.add("yellow");
    list.add("blue");
    list.add("green");
%>
<c:forEach var="color" items="<%=list%>" begin="0" end="3" step="1" varStatus="status">
    ${!status.first} -> 第一个Item
    ${!status.last} -> 最后一个Item
    ${color} <br/>
</c:forEach>

• forTokens 标签

<c:forTokens var="token" items="Spring,Summer|autumn,winter" delims="|,">
    ${token}
</c:forTokens> 

• formatDate 标签

<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<fmt:formatDate type="date" value="${withdraw.createDate}" />

• EL表达式的判断符号

                     等于  ==    eq 
                   不等于  !=    ne、neq
                     大于  >     gt 
                     小于  <     lt 
                 大于等于  >=    ge、gte
                 小于等于  <=    le、lte
                       与  &&    and 
                       或  ||    or 
                       非  !     not 
                       加  + 
                       减  - 
                       乘  * 
                     除以  /     div 
                     求莫  %     mod