Java 自由标记：freemarker.core.InvalidReferenceException
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Free Marker: freemarker.core.InvalidReferenceException
提问by Pathfinder92
I use freemarker templates and i have given the code within the ftl file below.
我使用 freemarker 模板，并在下面的 ftl 文件中提供了代码。
<#if (actionErrors?exists && actionErrors?size > 0)>
<ul>
<#list actionErrors as error>
<li><span<#rt/>
<#if parameters.cssClass?exists>
class="${parameters.cssClass?html}"<#rt/>
</#if>
<#if parameters.cssStyle?exists>
style="${parameters.cssStyle?html}"<#rt/>
</#if>
>${error}</span></li>
</#list>
</ul>
</#if>
The above code gives the following error.
上面的代码给出了以下错误。
freemarker.core.InvalidReferenceException: Expression error is undefined on line 33
freemarker.core.InvalidReferenceException：第 33 行未定义表达式错误
I wrapped the ${error} with <#if error.value??> and tried again. Still it gave the same issue. Then i used the ${error.value!'N/A'} as mentioned here. Still it didn't resolve the issue. Please help me with this.
我用 <#if error.value??> 包裹了 ${error} 并再次尝试。它仍然给出了同样的问题。然后我使用了这里提到的 ${error.value!'N/A'} 。仍然没有解决问题。请帮我解决一下这个。
Thank you in advance.
先感谢您。
Thank you.
谢谢你。
回答by Charles Forsythe
As already mentioned, the errorvalue appears not to have been set. When you do this:
如前所述，该error值似乎尚未设置。当你这样做时：
${error.value!"Default"}
...you are providing a default in case the valueattribute of erroris not set. It still assumes that erroris set so that it can get the valueattribute off it. If you do this:
...如果未设置value属性，您将提供默认值error。它仍然假定error已设置，以便它可以从中获取value属性。如果你这样做：
${(error.value)!"Default"}
...the default will apply if eithererroror error.valueis not set. The parentheses say "apply the default to the enclosed expression." If Freemarker encounters a missing value anywhere while parsing the enclosed expression, it applies the default.
...默认将适用，如果任一error或者error.value未设置。括号表示“将默认值应用于封闭的表达式”。如果 Freemarker 在解析封闭表达式时在任何地方遇到缺失值，它会应用默认值。
This also works with the ??operator:
这也适用于??运营商：
<#if (error.value)??>The entire expression error.value is valid</#if>
