XPath最通俗的教程(ZZ)

  以下是本人找到的最完整最易懂的XPath教程,不敢私藏,拿出来与大家分享。帮我点旁边的google广告呀。

实例 1
基本的XPath语法类似于在一个文件系统中定位文件,如果路径以斜线 / 开始, 那么该路径就表示到一个元素的绝对路径

/AAA

选择根元素AAA


     <
AAA> 
          <BBB/> 
          <CCC/> 
          <BBB/> 
          <BBB/> 
          <DDD> 
               <BBB/> 
          </DDD> 
          <CCC/> 
     </
AAA>

 

/AAA/CCC

选择AAA的所有CCC子元素


     <AAA> 
          <BBB/> 
          <
CCC/> 
          <BBB/> 
          <BBB/> 
          <DDD> 
               <BBB/> 
          </DDD> 
          <
CCC/> 
     </AAA>

 

/AAA/DDD/BBB

选择AAA的子元素DDD的所有子元素


     <AAA> 
          <BBB/> 
          <CCC/> 
          <BBB/> 
          <BBB/> 
          <DDD> 
               <
BBB/> 
          </DDD> 
          <CCC/> 
     </AAA>

 

 

实例 2

如果路径以双斜线 // 开头, 则表示选择文档中所有满足双斜线//之后规则的元素(无论层级关系)

 

//BBB

选择所有BBB元素


     <AAA> 
          <
BBB/> 
          <CCC/> 
          <
BBB/> 
          <DDD> 
               <
BBB/> 
          </DDD> 
          <CCC> 
               <DDD> 
                    <
BBB/> 
                    <
BBB/> 
               </DDD> 
          </CCC> 
     </AAA>

 

//DDD/BBB

选择所有父元素是DDD的BBB元素


     <AAA> 
          <BBB/> 
          <CCC/> 
          <BBB/> 
          <DDD> 
               <
BBB/> 
          </DDD> 
          <CCC> 
               <DDD> 
                    <
BBB/> 
                    <
BBB/> 
               </DDD> 
          </CCC> 
     </AAA>

 

 

实例 3

星号 * 表示选择所有由星号之前的路径所定位的元素

 

/AAA/CCC/DDD/*

选择所有路径依附于/AAA/CCC/DDD的元素


     <AAA> 
          <XXX> 
               <DDD> 
                    <BBB/> 
                    <BBB/> 
                    <EEE/> 
                    <FFF/> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD> 
                    <
BBB/> 
                    <
BBB/> 
                    <
EEE/> 
                    <
FFF/> 
               </DDD> 
          </CCC> 
          <CCC> 
               <BBB> 
                    <BBB> 
                         <BBB/> 
                    </BBB> 
               </BBB> 
          </CCC> 
     </AAA>

 

/*/*/*/BBB

选择所有的有3个祖先元素的BBB元素


     <AAA> 
          <XXX> 
               <DDD> 
                    <
BBB/> 
                    <
BBB/> 
                    <EEE/> 
                    <FFF/> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD> 
                    <
BBB/> 
                    <
BBB/> 
                    <EEE/> 
                    <FFF/> 
               </DDD> 
          </CCC> 
          <CCC> 
               <BBB> 
                    <
BBB> 
                         <BBB/> 
                    </
BBB> 
               </BBB> 
          </CCC> 
     </AAA>

 

//*

选择所有元素


     <
AAA> 
          <
XXX> 
               <
DDD> 
                    <
BBB/> 
                    <
BBB/> 
                    <
EEE/> 
                    <
FFF/> 
               </
DDD> 
          </
XXX> 
          <
CCC> 
               <
DDD> 
                    <
BBB/> 
                    <
BBB/> 
                    <
EEE/> 
                    <
FFF/> 
               </
DDD> 
          </
CCC> 
          <
CCC> 
               <
BBB> 
                    <
BBB> 
                         <
BBB/> 
                    </
BBB> 
               </
BBB> 
          </
CCC> 
     </
AAA>

 

 

 

实例 4

方块号里的表达式可以进一步的指定元素, 其中数字表示元素在选择集里的位置, 而last()函数则表示选择集中的最后一个元素.

 

/AAA/BBB[1]

选择AAA的第一个BBB子元素


     <AAA> 
          <
BBB/> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
     </AAA>

 

/AAA/BBB[last()]

选择AAA的最后一个BBB子元素


     <AAA> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <
BBB/> 
     </AAA>

 

 

 

实例 5

//@id

选择所有的id属性


     <AAA> 
          <BBB
 id = "b1"/> 
          <BBB
 id = "b2"/> 
          <BBB name = "bbb"/> 
          <BBB/> 
     </AAA>

 

//BBB[@id]

选择有id属性的BBB元素


     <AAA> 
          <
BBB id = "b1"/> 
          <
BBB id = "b2"/> 
          <BBB name = "bbb"/> 
          <BBB/> 
     </AAA>

 

//BBB[@name]

选择有name属性的BBB元素


     <AAA> 
          <BBB id = "b1"/> 
          <BBB id = "b2"/> 
          <
BBB name = "bbb"/> 
          <BBB/> 
     </AAA>

 

//BBB[@*]

选择有任意属性的BBB元素


     <AAA> 
          <
BBB id = "b1"/> 
          <
BBB id = "b2"/> 
          <
BBB name = "bbb"/> 
          <BBB/> 
     </AAA>

 

//BBB[not(@*)]

选择没有属性的BBB元素


     <AAA> 
          <BBB id = "b1"/> 
          <BBB id = "b2"/> 
          <BBB name = "bbb"/> 
          <
BBB/> 
     </AAA>

 

 

 

实例 6

属性的值可以被用来作为选择的准则, normalize-space函数删除了前部和尾部的空格, 并且把连续的空格串替换为一个单一的空格

 

//BBB[@id='b1']

选择含有属性id且其值为'b1'的BBB元素


     <AAA> 
          <
BBB id = "b1"/> 
          <BBB name = " bbb "/> 
          <BBB name = "bbb"/> 
     </AAA>

 

//BBB[@name='bbb']

选择含有属性name且其值为'bbb'的BBB元素


     <AAA> 
          <BBB id = "b1"/> 
          <BBB name = " bbb "/> 
          <
BBB name = "bbb"/> 
     </AAA>

 

//BBB[normalize-space(@name)='bbb']

选择含有属性name且其值(在用normalize-space函数去掉前后空格后)为'bbb'的BBB元素


     <AAA> 
          <BBB id = "b1"/> 
          <
BBB name = " bbb "/> 
          <
BBB name = "bbb"/> 
     </AAA>

 

 

 

实例 7

count()函数可以计数所选元素的个数

 

//*[count(BBB)=2]

选择含有2个BBB子元素的元素


     <AAA> 
          <CCC> 
               <BBB/> 
               <BBB/> 
               <BBB/> 
          </CCC> 
          <
DDD> 
               <BBB/> 
               <BBB/> 
          </
DDD> 
          <EEE> 
               <CCC/> 
               <DDD/> 
          </EEE> 
     </AAA>

 

//*[count(*)=2]

选择含有2个子元素的元素


     <AAA> 
          <CCC> 
               <BBB/> 
               <BBB/> 
               <BBB/> 
          </CCC> 
          <
DDD> 
               <BBB/> 
               <BBB/> 
          </
DDD> 
          <
EEE> 
               <CCC/> 
               <DDD/> 
          </
EEE> 
     </AAA>

 

//*[count(*)=3]

选择含有3个子元素的元素


     <
AAA> 
          <
CCC> 
               <BBB/> 
               <BBB/> 
               <BBB/> 
          </
CCC> 
          <DDD> 
               <BBB/> 
               <BBB/> 
          </DDD> 
          <EEE> 
               <CCC/> 
               <DDD/> 
          </EEE> 
     </
AAA>

 

 

 

实例 8

name()函数返回元素的名称, start-with()函数在该函数的第一个参数字符串是以第二个参数字符开始的情况返回true, contains()函数当其第一个字符串参数包含有第二个字符串参数时返回true.

 

//*[name()='BBB']

选择所有名称为BBB的元素(这里等价于//BBB)


     <AAA> 
          <BCC> 
               <
BBB/> 
               <
BBB/> 
               <
BBB/> 
          </BCC> 
          <DDB> 
               <
BBB/> 
               <
BBB/> 
          </DDB> 
          <BEC> 
               <CCC/> 
               <DBD/> 
          </BEC> 
     </AAA>

 

//*[starts-with(name(),'B')]

选择所有名称以"B"起始的元素


     <AAA> 
          <
BCC> 
               <
BBB/> 
               <
BBB/> 
               <
BBB/> 
          </
BCC> 
          <DDB> 
               <
BBB/> 
               <
BBB/> 
          </DDB> 
          <
BEC> 
               <CCC/> 
               <DBD/> 
          </
BEC> 
     </AAA>

 

//*[contains(name(),'C')]

选择所有名称包含"C"的元素


     <AAA> 
          <
BCC> 
               <BBB/> 
               <BBB/> 
               <BBB/> 
          </
BCC> 
          <DDB> 
               <BBB/> 
               <BBB/> 
          </DDB> 
          <
BEC> 
               <
CCC/> 
               <DBD/> 
          </
BEC> 
     </AAA>

 

 

 

实例 10

多个路径可以用分隔符 | 合并在一起

 

//CCC | //BBB

选择所有的CCC和BBB元素


     <AAA> 
          <
BBB/> 
          <
CCC/> 
          <DDD> 
               <
CCC/> 
          </DDD> 
          <EEE/> 
     </AAA>

 

/AAA/EEE | //BBB

选择所有的BBB元素和所有是AAA的子元素的EEE元素


     <AAA> 
          <
BBB/> 
          <CCC/> 
          <DDD> 
               <CCC/> 
          </DDD> 
          <
EEE/> 
     </AAA>

 

/AAA/EEE | //DDD/CCC | /AAA | //BBB

可以合并的路径数目没有限制


     <
AAA> 
          <
BBB/> 
          <CCC/> 
          <DDD> 
               <
CCC/> 
          </DDD> 
          <
EEE/> 
     </
AAA>

 

 

 

实例 11

child轴(axis)包含上下文节点的子元素, 作为默认的轴,可以忽略不写.

 

/AAA

等价于 /child::AAA


     <
AAA> 
          <BBB/> 
          <CCC/> 
     </
AAA>

 

/child::AAA

等价于/AAA


     <
AAA> 
          <BBB/> 
          <CCC/> 
     </
AAA>

 

/AAA/BBB

等价于/child::AAA/child::BBB


     <AAA> 
          <
BBB/> 
          <CCC/> 
     </AAA>

 

/child::AAA/child::BBB

等价于/AAA/BBB


     <AAA> 
          <
BBB/> 
          <CCC/> 
     </AAA>

 

/child::AAA/BBB

二者都可以被合并


     <AAA> 
          <
BBB/> 
          <CCC/> 
     </AAA>

 

 

 

 

实例 12

descendant (后代)轴包含上下文节点的后代,一个后代是指子节点或者子节点的子节点等等, 因此descendant轴不会包含属性和命名空间节点.

 

/descendant::*

选择文档根元素的所有后代.即所有的元素被选择


     <
AAA> 
          <
BBB> 
               <
DDD> 
                    <
CCC> 
                         <
DDD/> 
                         <
EEE/> 
                    </
CCC> 
               </
DDD> 
          </
BBB> 
          <
CCC> 
               <
DDD> 
                    <
EEE> 
                         <
DDD> 
                              <
FFF/> 
                         </
DDD> 
                    </
EEE> 
               </
DDD> 
          </
CCC> 
     </
AAA>

 

/AAA/BBB/descendant::*

选择/AAA/BBB的所有后代元素


     <AAA> 
          <BBB> 
               <
DDD> 
                    <
CCC> 
                         <
DDD/> 
                         <
EEE/> 
                    </
CCC> 
               </
DDD> 
          </BBB> 
          <CCC> 
               <DDD> 
                    <EEE> 
                         <DDD> 
                              <FFF/> 
                         </DDD> 
                    </EEE> 
               </DDD> 
          </CCC> 
     </AAA>

 

//CCC/descendant::*

选择在祖先元素中有CCC的所有元素


     <AAA> 
          <BBB> 
               <DDD> 
                    <CCC> 
                         <
DDD/> 
                         <
EEE/> 
                    </CCC> 
               </DDD> 
          </BBB> 
          <CCC> 
               <
DDD> 
                    <
EEE> 
                         <
DDD> 
                              <
FFF/> 
                         </
DDD> 
                    </
EEE> 
               </
DDD> 
          </CCC> 
     </AAA>

 

//CCC/descendant::DDD

选择所有以CCC为祖先元素的DDD元素


     <AAA> 
          <BBB> 
               <DDD> 
                    <CCC> 
                         <
DDD/> 
                         <EEE/> 
                    </CCC> 
               </DDD> 
          </BBB> 
          <CCC> 
               <
DDD> 
                    <EEE> 
                         <
DDD> 
                              <FFF/> 
                         </
DDD> 
                    </EEE> 
               </
DDD> 
          </CCC> 
     </AAA>

 

 

 

 

实例 13

parent轴(axis)包含上下文节点的父节点, 如果有父节点的话

 

//DDD/parent::*

选择DDD元素的所有父节点


     <AAA> 
          <
BBB> 
               <DDD> 
                    <
CCC> 
                         <DDD/> 
                         <EEE/> 
                    </
CCC> 
               </DDD> 
          </
BBB> 
          <
CCC> 
               <DDD> 
                    <
EEE> 
                         <DDD> 
                              <FFF/> 
                         </DDD> 
                    </
EEE> 
               </DDD> 
          </
CCC> 
     </AAA>

 

 

 

 

实例 14

ancestor轴(axis)包含上下节点的祖先节点, 该祖先节点由其上下文节点的父节点以及父节点的父节点等等诸如此类的节点构成,所以ancestor轴总是包含有根节点,除非上下文节点就是根节点本身.

 

/AAA/BBB/DDD/CCC/EEE/ancestor::*

选择一个绝对路径上的所有节点


     <
AAA> 
          <
BBB> 
               <
DDD> 
                    <
CCC> 
                         <DDD/> 
                         <EEE/> 
                    </
CCC> 
               </
DDD> 
          </
BBB> 
          <CCC> 
               <DDD> 
                    <EEE> 
                         <DDD> 
                              <FFF/> 
                         </DDD> 
                    </EEE> 
               </DDD> 
          </CCC> 
     </
AAA>

 

//FFF/ancestor::*

选择FFF元素的祖先节点


     <
AAA> 
          <BBB> 
               <DDD> 
                    <CCC> 
                         <DDD/> 
                         <EEE/> 
                    </CCC> 
               </DDD> 
          </BBB> 
          <
CCC> 
               <
DDD> 
                    <
EEE> 
                         <
DDD> 
                              <FFF/> 
                         </
DDD> 
                    </
EEE> 
               </
DDD> 
          </
CCC> 
     </
AAA>

 

 

 

 

实例 15

following-sibling轴(axis)包含上下文节点之后的所有兄弟节点

 

/AAA/BBB/following-sibling::*

 


     <AAA> 
          <BBB> 
               <CCC/> 
               <DDD/> 
          </BBB> 
          <
XXX> 
               <DDD> 
                    <EEE/> 
                    <DDD/> 
                    <CCC/> 
                    <FFF/> 
                    <FFF> 
                         <GGG/> 
                    </FFF> 
               </DDD> 
          </
XXX> 
          <
CCC> 
               <DDD/> 
          </
CCC> 
     </AAA>

 

//CCC/following-sibling::*

 


     <AAA> 
          <BBB> 
               <CCC/> 
               <
DDD/> 
          </BBB> 
          <XXX> 
               <DDD> 
                    <EEE/> 
                    <DDD/> 
                    <CCC/> 
                    <
FFF/> 
                    <
FFF> 
                         <GGG/> 
                    </
FFF> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

 

 

 

实例 16

preceding-sibling 轴(axis)包含上下文节点之前的所有兄弟节点

 

/AAA/XXX/preceding-sibling::*

 


     <AAA> 
          <
BBB> 
               <CCC/> 
               <DDD/> 
          </
BBB> 
          <XXX> 
               <DDD> 
                    <EEE/> 
                    <DDD/> 
                    <CCC/> 
                    <FFF/> 
                    <FFF> 
                         <GGG/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

//CCC/preceding-sibling::*

 


     <AAA> 
          <
BBB> 
               <CCC/> 
               <DDD/> 
          </
BBB> 
          <
XXX> 
               <DDD> 
                    <
EEE/> 
                    <
DDD/> 
                    <CCC/> 
                    <FFF/> 
                    <FFF> 
                         <GGG/> 
                    </FFF> 
               </DDD> 
          </
XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

 

 

 

实例 17

following轴(axis)包含同一文档中按文档顺序位于上下文节点之后的所有节点, 除了祖先节点,属性节点和命名空间节点

 

/AAA/XXX/following::*

 


     <AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ> 
                    <DDD/> 
                    <DDD> 
                         <EEE/> 
                    </DDD> 
               </ZZZ> 
               <FFF> 
                    <GGG/> 
               </FFF> 
          </BBB> 
          <XXX> 
               <DDD> 
                    <EEE/> 
                    <DDD/> 
                    <CCC/> 
                    <FFF/> 
                    <FFF> 
                         <GGG/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <
CCC> 
               <
DDD/> 
          </
CCC> 
     </AAA>

 

//ZZZ/following::*

 


     <AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ> 
                    <DDD/> 
                    <DDD> 
                         <EEE/> 
                    </DDD> 
               </ZZZ> 
               <
FFF> 
                    <
GGG/> 
               </
FFF> 
          </BBB> 
          <
XXX> 
               <
DDD> 
                    <
EEE/> 
                    <
DDD/> 
                    <
CCC/> 
                    <
FFF/> 
                    <
FFF> 
                         <
GGG/> 
                    </
FFF> 
               </
DDD> 
          </
XXX> 
          <
CCC> 
               <
DDD/> 
          </
CCC> 
     </AAA>

 

 

 

 

实例 18

preceding(axis)包含同一文档中按文档顺序位于上下文节点之前的所有节点, 除了祖先节点,属性节点和命名空间节点

 

/AAA/XXX/preceding::*

 


     <AAA> 
          <
BBB> 
               <
CCC/> 
               <
ZZZ> 
                    <
DDD/> 
               </
ZZZ> 
          </
BBB> 
          <XXX> 
               <DDD> 
                    <EEE/> 
                    <DDD/> 
                    <CCC/> 
                    <FFF/> 
                    <FFF> 
                         <GGG/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

//GGG/preceding::*

 


     <AAA> 
          <
BBB> 
               <
CCC/> 
               <
ZZZ> 
                    <
DDD/> 
               </
ZZZ> 
          </
BBB> 
          <XXX> 
               <DDD> 
                    <
EEE/> 
                    <
DDD/> 
                    <
CCC/> 
                    <
FFF/> 
                    <FFF> 
                         <GGG/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

 

 

 

实例 19

descendant-or-self 轴(axis)包含上下文节点本身和该节点的后代节点

 

/AAA/XXX/descendant-or-self::*

 


     <AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ> 
                    <DDD/> 
               </ZZZ> 
          </BBB> 
          <
XXX> 
               <
DDD> 
                    <
EEE/> 
                    <
DDD/> 
                    <
CCC/> 
                    <
FFF/> 
                    <
FFF> 
                         <
GGG/> 
                    </
FFF> 
               </
DDD> 
          </
XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

//CCC/descendant-or-self::*

 


     <AAA> 
          <BBB> 
               <
CCC/> 
               <ZZZ> 
                    <DDD/> 
               </ZZZ> 
          </BBB> 
          <XXX> 
               <DDD> 
                    <EEE/> 
                    <DDD/> 
                    <
CCC/> 
                    <FFF/> 
                    <FFF> 
                         <GGG/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <
CCC> 
               <
DDD/> 
          </
CCC> 
     </AAA>

 

 

 

 

实例 20

ancestor-or-self 轴(axis)包含上下文节点本身和该节点的祖先节点

 

/AAA/XXX/DDD/EEE/ancestor-or-self::*

 


     <
AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ> 
                    <DDD/> 
               </ZZZ> 
          </BBB> 
          <
XXX> 
               <
DDD> 
                    <
EEE/> 
                    <DDD/> 
                    <CCC/> 
                    <FFF/> 
                    <FFF> 
                         <GGG/> 
                    </FFF> 
               </
DDD> 
          </
XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </
AAA>

 

//GGG/ancestor-or-self::*

 


     <
AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ> 
                    <DDD/> 
               </ZZZ> 
          </BBB> 
          <
XXX> 
               <
DDD> 
                    <EEE/> 
                    <DDD/> 
                    <CCC/> 
                    <FFF/> 
                    <
FFF> 
                         <
GGG/> 
                    </
FFF> 
               </
DDD> 
          </
XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </
AAA>

 

 

 

 

实例 21

ancestor, descendant, following, preceding 和self轴(axis)分割了XML文档(忽略属性节点和命名空间节点), 不能交迭, 而一起使用则包含所有节点

 

//GGG/ancestor::*

 


     <
AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ/> 
          </BBB> 
          <
XXX> 
               <
DDD> 
                    <EEE/> 
                    <
FFF> 
                         <HHH/> 
                         <GGG> 
                              <JJJ> 
                                   <QQQ/> 
                              </JJJ> 
                              <JJJ/> 
                         </GGG> 
                         <HHH/> 
                    </
FFF> 
               </
DDD> 
          </
XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </
AAA>

 

//GGG/descendant::*

 


     <AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ/> 
          </BBB> 
          <XXX> 
               <DDD> 
                    <EEE/> 
                    <FFF> 
                         <HHH/> 
                         <GGG> 
                              <
JJJ> 
                                   <
QQQ/> 
                              </
JJJ> 
                              <
JJJ/> 
                         </GGG> 
                         <HHH/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

//GGG/following::*

 


     <AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ/> 
          </BBB> 
          <XXX> 
               <DDD> 
                    <EEE/> 
                    <FFF> 
                         <HHH/> 
                         <GGG> 
                              <JJJ> 
                                   <QQQ/> 
                              </JJJ> 
                              <JJJ/> 
                         </GGG> 
                         <
HHH/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <
CCC> 
               <
DDD/> 
          </
CCC> 
     </AAA>

 

//GGG/preceding::*

 


     <AAA> 
          <
BBB> 
               <
CCC/> 
               <
ZZZ/> 
          </
BBB> 
          <XXX> 
               <DDD> 
                    <
EEE/> 
                    <FFF> 
                         <
HHH/> 
                         <GGG> 
                              <JJJ> 
                                   <QQQ/> 
                              </JJJ> 
                              <JJJ/> 
                         </GGG> 
                         <HHH/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

//GGG/self::*

 


     <AAA> 
          <BBB> 
               <CCC/> 
               <ZZZ/> 
          </BBB> 
          <XXX> 
               <DDD> 
                    <EEE/> 
                    <FFF> 
                         <HHH/> 
                         <
GGG> 
                              <JJJ> 
                                   <QQQ/> 
                              </JJJ> 
                              <JJJ/> 
                         </
GGG> 
                         <HHH/> 
                    </FFF> 
               </DDD> 
          </XXX> 
          <CCC> 
               <DDD/> 
          </CCC> 
     </AAA>

 

//GGG/ancestor::* | //GGG/descendant::* | //GGG/following::* | //GGG/preceding::* | //GGG/self::*

 


     <
AAA> 
          <
BBB> 
               <
CCC/> 
               <
ZZZ/> 
          </
BBB> 
          <
XXX> 
               <
DDD> 
                    <
EEE/> 
                    <
FFF> 
                         <
HHH/> 
                         <
GGG> 
                              <
JJJ> 
                                   <
QQQ/> 
                              </
JJJ> 
                              <
JJJ/> 
                         </
GGG> 
                         <
HHH/> 
                    </
FFF> 
               </
DDD> 
          </
XXX> 
          <
CCC> 
               <
DDD/> 
          </
CCC> 
     </
AAA>

 

 

 

 

实例 22

div运算符做浮点除法运算, mod运算符做求余运算, floor函数返回不大于参数的最大整数(趋近于正无穷), ceiling返回不小于参数的最小整数(趋近于负无穷)

 

//BBB[position() mod 2 = 0 ]

选择偶数位置的BBB元素


     <AAA> 
          <BBB/> 
          <
BBB/> 
          <BBB/> 
          <
BBB/> 
          <BBB/> 
          <
BBB/> 
          <BBB/> 
          <
BBB/> 
          <CCC/> 
          <CCC/> 
          <CCC/> 
     </AAA>

 

//BBB[ position() = floor(last() div 2 + 0.5) or position() = ceiling(last() div 2 + 0.5) ]

选择中间的BBB元素


     <AAA> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <
BBB/> 
          <
BBB/> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <CCC/> 
          <CCC/> 
          <CCC/> 
     </AAA>

 

//CCC[ position() = floor(last() div 2 + 0.5) or position() = ceiling(last() div 2 + 0.5) ]

选择中间的CCC元素


     <AAA> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <BBB/> 
          <CCC/> 
          <
CCC/> 
          <CCC/> 
     </AAA>