<logic:present>：判断数据是否存在
<logic:notPresent>：判断数据是否不存在
标签属性：
cookie，header，name，parameter，user，property，scope
<body>
<%request.setAttribute("name", "xiaoming");%>
<logic:present name="name" scope="request">
存在
</logic:present>
<logic:notPresent name="name" scope="request">
不存在
</logic:notPresent>
</body>
<logic:empty>：判断数据是否为空
<logic:notEmpty>：判断数据是否不为空
<body>
<%
List<String> list = new ArrayList<String>();
request.setAttribute("list", list);
%>
<jsp:useBean id="testbean" class="com.bean.TestBean" scope="request"></jsp:useBean>
<jsp:setProperty name="testbean" property="name" value="xiaot"></jsp:setProperty>
<logic:empty name="list" scope="request">
list为空
</logic:empty>
<logic:notEmpty name="testbean" property="name" scope="request">
TestBean中的name不为null
</logic:notEmpty>
</body>
关系运算标签：
<logic:equal>：判断是否相等
<logic:notEqual>：是否不等
<logic:greaterEqual>：是否大于等于
<logic:lessEqual>：是否小于等于
<logic:lessThan>：是否小于
<logic:greaterThan>：是否大于
<logic:iterate>
提供迭代输出功能
<body>
<%
String arr[] = {"element1","element2","element3"};
request.setAttribute("arr", arr);
List<String> list = new ArrayList<String>();
list.add("a");
list.add("b");
list.add("c");
request.setAttribute("list", list);
Map<String, String> map = new HashMap<String, String>();
map.put("map1","map1");
map.put("map2","map2");
map.put("map3","map3");
request.setAttribute("map", map);
%>
<h3>输出数组</h3>
<logic:iterate id="id" name="arr" scope="request">
<li>数组：${id}</li>
</logic:iterate>
<h3>输出集合</h3>
<logic:iterate id="id1" name="list" scope="request">
<li>集合：${id1}</li>
</logic:iterate>
<h3>输出map</h3>
<logic:iterate id="id2" name="map" scope="request">
<li>map：${id2.key}--${id2.value}</li>
</logic:iterate>
</body>
页面输出：
输出数组
数组：element1
数组：element2
数组：element3
输出集合
集合：a
集合：b
集合：c
输出map
map：map3--map3
map：map2--map2
map：map1--map1
<logic:redirect>
页面重定向操作
struts-config中注册：
<global-forwards>
<forward name="success" path="/jsp/success.jsp"></forward>
</global-forwards>
JSP：
<body> <logic:redirect forward="success" /> </body>