本文介绍了JSTL和哈希图不起作用的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
在servlet中,我有:
In a servlet I have:
HashMap eventsByDayNo = new HashMap();
eventsByDayNo.put (new Integer(12), "day 12 info");
eventsByDayNo.put (new Integer(11), "day 11 info");
eventsByDayNo.put (new Integer(15), "day 15 info");
eventsByDayNo.put (new Integer(16), "day 16 info");
request.setAttribute("eventsByDayNo", eventsByDayNo);
request.setAttribute("daysInMonth", new Integer(31));
在一个jsp中,我有:
And in a jsp I have:
<c:forEach var="dn" begin="1" end="${daysInMonth}" step="1" varStatus="status">
Day Number=<c:out value="${dn}" /> Value=<c:out value="${eventsByDayNo[dn]}" /><br>
</c:forEach>
上面的JSTL可以正常工作,但是如果我尝试抵消日期编号<c:out value="${eventsByDayNo[dn+3]}" />
没有哈希表项没有被打印.关于为什么不的任何答案?
The above JSTL works fine, but if I try to offset the day number <c:out value="${eventsByDayNo[dn+3]}" />
none of the hashmap entries are not printed. Any answers as to why not?
以上只是我的实际应用的概念证明.
The above is just a proof of concept for my real application.
推荐答案
我的猜测是dn+3
具有类型java.lang.Double
,而不是java.lang.Integer
(您可能会期望).
My guess is that dn+3
has type java.lang.Double
, not java.lang.Integer
(which you may expect).
<ul>
<c:forEach var="dn" begin="1" end="${daysInMonth}" step="1">
<li>
<c:set var="dnplus3" value="${dn+3}" />
dn=<c:out value="${dn}" />
dnplus3=<c:out value="${dnplus3}" />
class=<c:out value="${dnplus3.class.name}" />
</li>
</c:forEach>
</ul>
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