无涯教程-XPath - Predicate

无涯教程
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条件是指用方括号括起来的XPath表达式。它指的是出于某些条件限制节点集中的选定节点。例如，

S.No. Predicate & 描述
1

/class/student [1]

选择第一个学生元素，它是类元素的子元素。
2

/class/student [last()]

选择最后一个学生元素，它是类元素的子元素。
3

/class/student [@rolllno=493]

选择rollno 493的学生元素。
4

/class/student[marks>85]

选择marks> 85的学生元素。

示例

本示例通过遍历每个学生来创建一个<student>元素及其详细信息的表格。它计算学生节点的位置，然后打印学生详细信息以及序列号。

students.xml

<?xml version = "1.0"?>
<?xml-stylesheet type = "text/xsl" href = "students.xsl"?>
<class>
   <student rollno = "393">
      <firstname>Dinkar</firstname>
      <lastname>Kad</lastname>
      <nickname>Dinkar</nickname>
      <marks>85</marks>
   </student>
   <student rollno = "493">
      <firstname>Vaneet</firstname>
      <lastname>Gupta</lastname>
      <nickname>Vinni</nickname>
      <marks>95</marks>
   </student>
   <student rollno = "593">
      <firstname>Jasvir</firstname>
      <lastname>Singh</lastname>
      <nickname>Jazz</nickname>
      <marks>90</marks>
   </student>
</class>

students.xsl

<?xml version = "1.0" encoding = "UTF-8"?>
<xsl:stylesheet version = "1.0"
   xmlns:xsl = "http://www.w3.org/1999/XSL/Transform">  

<xsl:template match = "/">
<html>
<body>
<h2>Students</h2>
<table border = "1">
<tr bgcolor = "#9acd32">
<th>Roll No</th>
<th>First Name</th>
<th>Last Name</th>
<th>Nick Name</th>
<th>Marks</th>
</tr&gt


           </span><span class="tag">&lt;xsl:for-each</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"/class/student[1]"</span><span class="tag">&gt;</span><span class="pln">
              </span><span class="tag">&lt;tr&gt;</span><span class="pln">	 
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"@rollno"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"firstname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"lastname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"nickname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"marks"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">	 
              </span><span class="tag">&lt;/tr&gt;</span><span class="pln">	
           </span><span class="tag">&lt;/xsl:for-each&gt;</span><span class="pln">
				
           </span><span class="tag">&lt;xsl:for-each</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"/class/student[last()]"</span><span class="tag">&gt;</span><span class="pln">
              </span><span class="tag">&lt;tr&gt;</span><span class="pln">	 
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"@rollno"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"firstname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"lastname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"nickname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"marks"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">	 
              </span><span class="tag">&lt;/tr&gt;</span><span class="pln">	
           </span><span class="tag">&lt;/xsl:for-each&gt;</span><span class="pln">

           </span><span class="tag">&lt;xsl:for-each</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"/class/student[@rollno=493]"</span><span class="tag">&gt;</span><span class="pln">
              </span><span class="tag">&lt;tr&gt;</span><span class="pln">	 
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"@rollno"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"firstname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"lastname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"nickname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"marks"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">	 
              </span><span class="tag">&lt;/tr&gt;</span><span class="pln">	
           </span><span class="tag">&lt;/xsl:for-each&gt;</span><span class="pln">

           </span><span class="tag">&lt;xsl:for-each</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"/class/student[marks &gt;</span><span class="pln"> 85]"&gt;
              </span><span class="tag">&lt;tr&gt;</span><span class="pln">	 
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"@rollno"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"firstname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"lastname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"nickname"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">
                 </span><span class="tag">&lt;td&gt;&lt;xsl:value-of</span><span class="pln"> </span><span class="atn">select</span><span class="pln"> </span><span class="pun">=</span><span class="pln"> </span><span class="atv">"marks"</span><span class="tag">/&gt;&lt;/td&gt;</span><span class="pln">	 
              </span><span class="tag">&lt;/tr&gt;</span><span class="pln">	
           </span><span class="tag">&lt;/xsl:for-each&gt;</span><span class="pln">


        </span><span class="tag">&lt;/table&gt;</span><span class="pln">

     </span><span class="tag">&lt;/body&gt;</span><span class="pln">
  </span><span class="tag">&lt;/html&gt;</span><span class="pln">



</xsl:template>
</xsl:stylesheet>

验证输出

Formatted predicate Output

参考链接

www.learnfk.com/xpath/xpath…

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