在 XSLT 中使用 fn:sum 和包含空值的节点集 [英] Using fn:sum in XSLT with node-set containing null-values

问题描述

我正在尝试使用 XSLT 和 XPath 函数 fn:sum 在 XML 中总结一组值.只要值不为空，这就可以正常工作，但事实并非如此.为了说明我的问题，我举了一个例子:

I'm trying to sum up a set of values in an XML using XSLT and XPath function fn:sum. This works fine as long as the values are non-null, however this is not the case. To illustrate my problem I've made an example:

<?xml version="1.0"?>

<xsl:stylesheet version="2.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fn="http://www.w3.org/2005/xpath-functions">

  <xsl:template match="/root">
    <root>
      <!-- Works fine for non-null values -->
      <sum><xsl:value-of select="fn:sum(values/value)" /></sum>
    </root>
  </xsl:template>
</xsl:stylesheet>

和 XML:

<?xml version="1.0"?>
<root>
  <values>
    <value>1</value>
    <value>2</value>
    <value>3</value>
    <value>4</value>
    <!-- Nullvalue -->
    <value />
  </values>
</root>

只要没有空值，示例就可以正常工作.我尝试了选择的各种变体，例如 <xsl:value-of select="fn:sum(values[value != '']/value)"/> (如您可能会注意到，没有多少 XSLT 导出 ;) ) 如何过滤掉空值?

The example works fine as long as there's no null-values. I've tried various variants of the select, such as <xsl:value-of select="fn:sum(values[value != '']/value)" /> (as you might notice, not much of an XSLT export ;) ) How can I filter out the null-values?

推荐答案

显式测试节点是否有内容:

Explicitly test that the nodes have content:

<sum><xsl:value-of select="fn:sum(values/value[text()])" /></sum>

我认为你提到的:

<xsl:value-of select="fn:sum(values[value != '']/value)" /> 

不起作用，因为节点是空的 - 它根本不包含文本节点，而 value != '' 测试空字符串 - 即，具有数据的文本节点长度为 0.

does not work, because the node is empty - it does not contain a text node at all, whereas value != '' tests for an empty string - that is, a text node having data of length 0.

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