Xpath定位

1.基本的XPath语法

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>

 

2.以双斜线 // 开头查询

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>

 

3.星号 * 表示选择所有由星号之前的路径所定位的元

/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>

 

4.[]的作

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, 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>

 

 

5.属性

//@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>

 

6.属性2

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

//BBB[@id='b1']

选择含有属性id且其值为'b1'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'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)'bbb'BBB元素


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

 

7.count()函数

//*[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>

 

8.name()函数

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>

9.string-length函数

string-length函数返回字符串的字符数,你应该用&lt;替代<, &gt;代替>

//*[string-length(name()) = 3]

选择名字长度为3的元素


     <AAA>
          <Q/>
          <SSSS/>
          <BB/>
          <CCC/>
          <DDDDDDDD/>
          <EEEE/>
     </AAA>

 

 

//*[string-length(name()) < 3]

选择名字长度小于3的元素


     <AAA>
          <Q/>
          <SSSS/>
          <BB/>
          <CCC/>
          <DDDDDDDD/>
          <EEEE/>
     </AAA>

 

 

//*[string-length(name()) > 3]

选择名字长度大于3的元素


     <AAA>
          <Q/>
          <SSSS/>
          <BB/>
          <CCC/>
          <DDDDDDDD/>
          <EEEE/>
     </AAA>

 

10.分隔符 |

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>

 

11.descendant (后代)

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>

 

12.parent

parent(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>

 

13.ancestor

ancestor(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>

 

14、following-sibling

 

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

/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>

 

15、preceding-sibling

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

/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>

 

十六、following

following(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>

 

十八、descendant-or-self

descendant-or-self (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>

 

十九、ancestor-or-self (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>

 

 

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