在 facelets 标记的属性中定义的 EL 表达式中连接字符串 [英] Concatenating strings within EL expression defined in an attribute of a facelets tag

问题描述

我需要为这样的属性编写一个 EL 表达式:

I need to write an EL expression for an attribute which goes something like this:

#{cc.attrs.appreciatedByCurrentUser ? (cc.attrs.count +'<br/>'+ (cc.attrs.count-1)) : ((cc.attrs.count+1) +'<br/>'+ cc.attrs.count)}

现在的问题是，这会产生错误，因为字符串无法连接，就像我这样做的方式.那么我该如何解决这个问题?

Now the problem is that this gives an error as strings cannot be concatenated, the way I am doing it. So how can I rectify this?

我使用的是带有 facelets 的 JSF 2.0.

我正在使用以下内联 javascript 解决问题

I'm resolving the issue using the following inline javascript

            <script type="text/javascript">
                var count=#{cc.attrs.count};
                document.write(#{cc.attrs.appreciatedByCurrentUser} ? (count-1) +'<br/>'+count  : count+'<br/>'+ (count+1));
            </script>

你能想到这方面的任何问题吗?

Can you think of any issue with this?

推荐答案

EL 中的字符串连接只能通过在表达式中内联来实现.+ 运算符在 EL 中只是一个求和运算符.此外，< 和 > 是 XML 属性中的无效字符，因此您必须对它们进行转义(并指示 escape="false"):

String concatenation in EL is only possible by just inlining in the expression. The + operator is in EL exclusively a sum operator. Further, < and > are invalid characters in XML attributes, so you have to escape them (and instruct <h:outputText> to not escape them once again by escape="false"):

<h:outputText value="#{cc.attrs.count}&lt;br/&gt;#{cc.attrs.count-1}" escape="false" rendered="#{cc.attrs.appreciatedByCurrentUser}" />
<h:outputText value="#{cc.attrs.count+1}&lt;br/&gt;#{cc.attrs.count}" escape="false" rendered="#{!cc.attrs.appreciatedByCurrentUser}" />

或者，您也可以使用 为表达式添加别名:

Alternatively, you can also use <c:set> to alias the expression:

<c:set var="appreciated" value="#{cc.attrs.count}&lt;br/&gt;#{cc.attrs.count-1}" />
<c:set var="notAppreciated" value="#{cc.attrs.count+1}&lt;br/&gt;#{cc.attrs.count}" />
<h:outputText value="#{cc.attrs.appreciatedByCurrentUser ? appreciated : notAppreciated}" escape="false" />

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