jstl

jstl  jsp标准标签库

一般用途的标签
迭代标签
条件标签
url标签

C标签
c_out标签（用于把运算结果输出到对象）
如果域对象有相同的属性名，他们的优先级是pageContext>request>session>appcation
request.setAttribute("abc","你好<a href='http://www.baidu.com'>baidu</a>");
需要<c:out value="${abc}" escapeXml="false"></c:out>
当然可以输出对象信息
<c:out value="${user.name}" escapeXml="false"></c:out>

c_set标签(设置)
<c:set var="abc" value="中国" scope="request"></c:set>
<c:out value="${abc}" escapeXml="false"></c:out>
在实际中运用不多

c:remove
<c:out value="${abc}" escapeXml="false"></c:out>
<c:remove var="abc" ></c:remove>
<c:out value="${abc}" escapeXml="false"></c:out>

c:catch
<c:catch var="abc">
<% int i=8/0; %>
</c:catch>
<c:out value="${abc}" escapeXml="false"></c:out>

条件标签
c:if  这是单分支判断
<%
request.setAttribute("abc","123");
%>
<c:if test="${a=='123'}">
ok
</c:if>
<c:if test="${a!='123'}">
no	ok
</c:if>

c:choose
<c:choose>
<c:when test="${a=1}">
1
</c：when>
<c:when test="${a=2}">
2
</c：when>
<c:otherwise>
其他
</c:otherwise>
</c:choose>

迭代标签
<c:foreach>
<%
ArrayList<Dog> a1=new ArrayList<Rat>();
Dog dog1=new Dog();
dog1.setName("小黄1");
Dog dog2=new Dog();
dog2.setName("小黄2");
Dog dog3=new Dog();
dog3.setName("小黄3");

a1.add(dog1);
a1.add(dog2);
a1.add(dog3);

request.setAttribute("dogs","a1");

%>
<%
ArrayList<Dog> a2=(ArrayList<Dog>)request.getAttribute("dogs");
%>
<c:forEach items="${a2}" var ="dog">
<c:out value="${dog.name}"/>
</c:forEach>

<c:forEach var="i" begin="1" end="10" step="3">
</c:forEach>

<c:forTokens>用于分隔字符
<c:forTokens items="aa,bb,cc,dd" delims="," var="temp">
<c:out value="${temp}"/>
</c:forTokens>

jstl细节问题
1.对象是在hashmap或haspset
<% Map map=new HashMap();
Dog dog1=new Dog();
dog1.setName("小黄1");
Dog dog2=new Dog();
dog2.setName("小黄2");
Dog dog3=new Dog();
dog3.setName("小黄3");

map.put("aa",dog1);
map.put("aa",dog2);
map.put("aa",dog3);
request.setAttribute("dogs",map);
%>

<c:forEach items="${dogs}" var ="per">
key=${per.key}值=${per.value.name}
</c:forEach>

<c:if test="$(empty dogs)">//判断集合是否为空
</c:if>

<c:import url="index.jsp">
<c:param name="name" value="123"/>
</c:import>
index.jsp页面获取name参数  ${parma.name}就行