JSTL,Bean和方法调用 [英] JSTL, Beans, and method calls
问题描述
< jsp:useBean id =pageBeanscope =requesttype =com.epicentric.page.website.PageBean/>
< c:set var =pageDividersvalue =<%= pageBean.getPageDividers()%> />
< c:set var =numColumnsvalue =$ {pageDividers.size()}/>
变量 pageDividers
是一个列表
对象。
我遇到这个问题:当我要求 pageDivider
的大小,抛出异常。我知道这是一个简单的JTSL错误 - 我做错了什么?
错误信息是:
当未指定默认命名空间时,必须使用前缀的函数大小
正确访问或调用我的 pageDividers
对象的方法
在JSTL中使用点运算符进行属性访问,需要调用 $ {pageDividers.size}
(no ()) getSize()
。
由于java.util.List提供了一个名为 size()
(而不是 getSize()
),您将无法使用该代码访问列表长度。
为了访问列表大小,JSTL提供 fn:length 函数,如
$ {fn:length(pageDividers)}
请注意,按顺序t o使用 fn 命名空间,您应该声明如下
<%@ taglib uri = http://java.sun.com/jsp/jstl/functionsprefix =fn%>
此外,同样的功能可以用于任何集合类型,也可以用于Strings。 p>
I'm working on a JSP where I need to call methods on object that come from a Bean. The previous version of the page does not use JSTL and it works properly. My new version has a set up like this:
<jsp:useBean id="pageBean" scope="request" type="com.epicentric.page.website.PageBean" />
<c:set var="pageDividers" value="<%= pageBean.getPageDividers() %>" />
<c:set var="numColumns" value="${pageDividers.size()}" />
The variable pageDividers
is a List
object.
I'm encountering this issue: when I ask for pageDivider
's size, an exception is thrown. I know this is a simple JTSL error -- what am I doing wrong?
The error message is:
The function size must be used with a prefix when a default namespace is not specified
How do I correctly access or call the methods of my pageDividers
object?
When using the dot operator for property access in JSTL, ${pageDividers.size}
(no () needed) results in a call to a method named getSize()
.
Since java.util.List offers a method called size()
(rather than getSize()
) you won't be able to access the list length by using that code.
In order to access to a list size, JSTL offers the fn:length function, used like
${fn:length(pageDividers)}
Note that in order to use the fn namespace, you should declare it as follows
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
In addition, the same function can be used with any collection type, and with Strings too.
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