Xpath 学习资料

收集了一份Xpath资料,分享
XML  强大的Xpath

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轴(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> 
       

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