jstl表达式中if else 语句如下：
<c:set var="age" value="25" scope="request"></c:set>
<c:choose>
<c:when test="${age>=16 }">
<font color="green">你是成年人</font>
</c:when>
<c:otherwise>
<font color="rad">你未成年</font>
</c:otherwise>
</c:choose>
JSTL语句中的循环表达式：
取数据的时候都需要用到EL表达式${}来取值如：
例1
<c:forEach begin="1" end="15">
<%out.println("正在执行foreach语句"); %>
</c:forEach>
例2
<%
UserDao.addUser("A", new User("A", "男", 31, "shibin123", true));
UserDao.addUser("B", new User("B", "女", 32, "shibin123", true));
UserDao.addUser("C", new User("C", "女", 23, "shibin123", true));
UserDao.addUser("D", new User("D", "女", 34, "shibin123", true));
UserDao.addUser("E", new User("E", "女", 21, "shibin123", true));
UserDao.addUser("F", new User("F", "女", 23, "shibin123", true));
UserDao.addUser("G", new User("G", "男", 24, "shibin123", true));
Map ma=DBUtil.getUsers();
List list=new ArrayList();
list.addAll(ma.values());
request.setAttribute("list", list);
%>
<c:forEach items="${list }" var="us">
${us.name},${us.age},${us.sex},${us.password}<br>
</c:forEach>
