xml 如果元素存在且非空，如何使用 XPath 判断？
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How to tell using XPath if an element is present and non empty?
提问by Charu Khurana
I have an input XML something on this line:
我在这一行有一个输入 XML：
<Holding id="12">
<Policy>
<HoldingForm tc="1">Individual</HoldingForm>
<PolNumber>848433</PolNumber>
<LineOfBusiness tc="1">Life</LineOfBusiness>
<CarrierCode>67644</CarrierCode>
</Policy>
</Holding>
My manipulation on this XML depends on if <PolNumber>(its an optional element in schema) has a value or not. I'm using Mule 3.3 xpathevaluator to do this and my XPath expression looks this:
我对这个 XML 的操作取决于<PolNumber>（它是模式中的一个可选元素）是否有值。我正在使用 Mule 3.3xpath评估器来执行此操作，我的 XPath 表达式如下所示：
<expression-filter expression="#[xpath('//acord:Holding/acord:Policy/acord:PolNumber').text != empty]"/>
This works fine as long as <PolNumber>element is present or <PolNumber/>is empty element. But if <PolNumber>is absent, above expression throws exception.
只要<PolNumber>元素存在或<PolNumber/>为空元素，就可以正常工作。但是如果<PolNumber>不存在，上面的表达式会抛出异常。
I tried using XPath booleanfunction but it returns truefor <PolNumber/>. Is there a better way of checking if an element is present and non-empty?
我试着用XPath的布尔函数，但返回true的<PolNumber/>。有没有更好的方法来检查元素是否存在且非空？
EDIT:
编辑：
This is the configuration of namespace manager in my mule config
这是我的 mule 配置中命名空间管理器的配置
<xm:namespace-manager includeConfigNamespaces="true">
<xm:namespace prefix="acord" uri="http://ACORD.org/Standards/Life/2" />
<xm:namespace prefix="soap" uri="http://schemas.xmlsoap.org/soap/encoding/" />
</xm:namespace-manager>
回答by Dimitre Novatchev
Use:
使用：
boolean(//acord:Holding/acord:Policy/acord:PolNumber/text()[1])
this produces true()if //acord:Holding/acord:Policy/acord:PolNumberhas a first text-node child, and false()otherwise.
这将产生true()，如果//acord:Holding/acord:Policy/acord:PolNumber有第一个文本节点孩子，和false()其他。
Do note: This is more efficient than counting all text-node children just to compare the count with 0.
请注意：这比仅将计数与 0 进行比较而计算所有文本节点子节点更有效。
回答by Jens Erat
You can use boolean(...)for checking if it's empty, but make sure to look insidethe element.
您可以boolean(...)用于检查它是否为空，但请确保查看元素内部。
boolean(//PolNumber/node())
This also works if other nodes are contained. If you want to limit to text nodes, replace node()by text(). You could want to use //text()instead, then the query will also yield true for text nodes inside other child elements of <PolNumber/>.
如果包含其他节点，这也适用。如果要限制为文本节点，请替换node()为text(). 您可能想//text()改用，然后查询也将为<PolNumber/>.
回答by user3190499
How about expression="#[?xpath('//acord:Holding/acord:Policy/acord:PolNumber').text != empty]"? This should work in in all situations
怎么样expression="#[?xpath('//acord:Holding/acord:Policy/acord:PolNumber').text != empty]"？这应该适用于所有情况
回答by Thomas Modeneis
Maybe I'm a bit late here, but answers are a bit confusing. This one will always returns false when text is blank or with spaces but no chars.
也许我在这里有点晚了，但答案有点令人困惑。当文本为空白或有空格但没有字符时，此方法将始终返回 false。
boolean//Holding/Policy/PolNumber/child/text()[normalize-space()]
回答by David Dossot
What about using countto get the number of text nodes:
如何使用count获取文本节点的数量：
<expression-filter
expression="#[xpath('count(//Holding/Policy/PolNumber/child::text())') != 0]"/>
