使用XSLT分组转换XML

<!-- 原始XML -->
<products>
  <product>
    <name>产品1</name>
    <category>类别1</category>
  </product>
  <product>
    <name>产品2</name>
    <category>类别1</category>
  </product>
  <product>
    <name>产品3</name>
    <category>类别2</category>
  </product>
</products>

<!-- XSLT模板 -->
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>
  
  <xsl:key name="category" match="product" use="category"/>
  
  <xsl:template match="/">
    <result>
      <xsl:for-each select="products/product[generate-id() = generate-id(key('category', category)[1])]">
        <category>
          <name><xsl:value-of select="category"/></name>
          <products>
            <xsl:apply-templates select="key('category', category)"/>
          </products>
        </category>
      </xsl:for-each>
    </result>
  </xsl:template>
  
  <xsl:template match="product">
    <product>
      <name><xsl:value-of select="name"/></name>
    </product>
  </xsl:template>
</xsl:stylesheet>

<!-- 转换后的XML -->
<result>
  <category>
    <name>类别1</name>
    <products>
      <product>
        <name>产品1</name>
      </product>
      <product>
        <name>产品2</name>
      </product>
    </products>
  </category>
  <category>
    <name>类别2</name>
    <products>
      <product>
        <name>产品3</name>
      </product>
    </products>
  </category>
</result>