jstl标签需要注意的问题
原来一直用struts,最近项目里有人用jstl,我也就顺便拿来用，感觉还是不错。
过程中碰到一些小的问题总结如下:
一。版本问题
jstl存在1.0和1.1的差异问题，用EL建议需要在1.1的版本下，1.1的URI的标志为:
<%
@ taglib uri
=
"
http://java.sun.com/jsp/jstl/core
"
prefix
=
"
c
"
%>
<% @ taglib uri = " http://java.sun.com/jsp/jstl/functions " prefix = " fn " %>
<% @ taglib uri = " http://java.sun.com/jsp/jstl/functions " prefix = " fn " %>
注意，1.0版本没有/jsp/.
如果用的1.0会出现如下异常
org.apache.jasper.JasperException:
/
public
/
left_tree.jsp(
100
,
24
) According to TLD or attribute directive in tag file, attribute items does not accept any expressions
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java: 510 )
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java: 375 )
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java: 314 )
org.apache.jasper.servlet.JspServlet.service(JspServlet.java: 264 )
javax.servlet.http.HttpServlet.service(HttpServlet.java: 802 )
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java: 75 )
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java: 77 )
com.wellsoon.zfzw.webapp.common.VabAccessFilter.doFilter(VabAccessFilter.java: 43 )
root cause
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java: 510 )
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java: 375 )
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java: 314 )
org.apache.jasper.servlet.JspServlet.service(JspServlet.java: 264 )
javax.servlet.http.HttpServlet.service(HttpServlet.java: 802 )
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java: 75 )
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java: 77 )
com.wellsoon.zfzw.webapp.common.VabAccessFilter.doFilter(VabAccessFilter.java: 43 )
root cause
二。打开ＥＬ
<%
@ page contentType
=
"
text/html;charset=gb2312
"
language
=
"
java
"
isELIgnored
=
"
false
"
%>
前提是容器支持２．０，即使支持默认也未必打开，最安全的方式就是显示打开 isELIgnored="false"
三.fn的用法
对于Vo里的一个List作length的计算或判断很方便
<
table
width
="160"
border
="0"
cellspacing
="0"
cellpadding
="4"
>
< c:forEach items ="${menuInfos}" var ="m" >
< c:if test ="${fn:length(m.subMenus)>0}" >
< tr >
< td >
< script language ="JavaScript" >
var tObj = new treeClass( " A1 " )
tObj.start();
tObj.m_start( " <c:out value= " ${m.menuModule} " /> " , 0 );
< c:forEach items = " ${m.subMenus} " var = " sub " >
tObj.add_Sub( " <c:out value= " ${sub.menuName} " /> " , " <%=path%>
<c:out value= " ${sub.url} " /> " , " mymain " );
</ c:forEach >
tObj.m_end();
tObj.end();
tObj.print();
</ script >
</ td >
</ tr >
</ c:if >
</ c:forEach >
</ table >
< c:forEach items ="${menuInfos}" var ="m" >
< c:if test ="${fn:length(m.subMenus)>0}" >
< tr >
< td >
< script language ="JavaScript" >
var tObj = new treeClass( " A1 " )
tObj.start();
tObj.m_start( " <c:out value= " ${m.menuModule} " /> " , 0 );
< c:forEach items = " ${m.subMenus} " var = " sub " >
tObj.add_Sub( " <c:out value= " ${sub.menuName} " /> " , " <%=path%>
<c:out value= " ${sub.url} " /> " , " mymain " );
</ c:forEach >
tObj.m_end();
tObj.end();
tObj.print();
</ script >
</ td >
</ tr >
</ c:if >
</ c:forEach >
</ table >
四.tld的声明可以在web.xml作显式声明也可以用http作直接URL声明
推荐用本地的方式.