XSLT函数——key()

       key(string,object)函数用于在一个索引中依照key值搜索对应的节点。参数string用于指定索引对象的名字，参数object用于指定查找时的key值。

       语法：key(string,object)

       参数：string字符串，必需；object字符串，必需

      返回值：节点集合

示例：

xml：

1. <?xml version="1.0" encoding="UTF-8"?>

2. <customers>

3.     <customer>

4.         <name>Alex</name>

5.         <age>25</age>

6.         <country>China</country>

7.     </customer>

8.     <customer>

9.         <name>Kin</name>

10.         <age>27</age>

11.         <country>England</country>

12.     </customer>

13.     <customer>

14.         <name>Kevin</name>

15.         <age>28</age>

16.         <country>China</country>

17.     </customer>

18.     <customer>

19.         <name>Bob</name>

20.         <age>25</age>

21.         <country>England</country>

22.     </customer>

23.     <customer>
            <name>John</name>
            <age>25</age>
            <country>America</country>
        </customer>
        <customer>
            <name>Joe</name>
            <age>32</age>
            <country>England</country>
        </customer>
        <customer>
            <name>Mark</name>
            <age>25</age>
            <country>America</country>
        </customer>
    </customers>

xslt：

1. <?xml version="1.0" encoding="UTF-8"?>
   <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
       <xsl:output method="xml" version="1.0" encoding="gb2312" indent="yes"/>    
       <xsl:key match="customer" name="customerKey" use="country"/>
       <xsl:template match="customers">
           <xsl:copy>
               <xsl:for-each select="customer[generate-id(.)=generate-id(key('customerKey',country))]">
                   <xsl:sort select="country"/>                
                   <xsl:for-each select="../customer[country=current()/country]">
                       <xsl:sort select="name"/>
                       <xsl:copy-of select="."/>                
                   </xsl:for-each>   
               </xsl:for-each>                
           </xsl:copy>    
       </xsl:template>
   </xsl:stylesheet>

结果：

1. <?xml version="1.0" encoding="gb2312"?>
   <customers>
       <customer>
           <name>John</name>
           <age>25</age>
           <country>America</country>
       </customer>
       <customer>
           <name>Mark</name>
           <age>25</age>
           <country>America</country>
       </customer>
       <customer>
           <name>Alex</name>
           <age>25</age>
           <country>China</country>
       </customer>
       <customer>
           <name>Kevin</name>
           <age>28</age>
           <country>China</country>
       </customer>
       <customer>
           <name>Bob</name>
           <age>25</age>
           <country>England</country>
       </customer>
       <customer>
           <name>Joe</name>
           <age>32</age>
           <country>England</country>
   </customer>
       <customer>
           <name>Kin</name>
           <age>27</age>
           <country>England</country>
       </customer>
   </customers>