XPath基础语法(1)

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Xpath是一种能够在XML文档中寻找信息的语言。它通过XML文档中的元素和属性来进行导航。

1. "/"

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

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

 /AAA/DDD/BBB:

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

2. "//"

 //BBB

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

 //DDD/BBB

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

3. "*":

 /AAA/CCC/DDD*/*/BBB

      <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>

//*

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

4. [1] , last()

/AAA/BBB[1]

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

/AAA/BBB[last()]

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

5. "@" :

//@id

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

//BBB[@id]

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

//BBB[@name]

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

//BBB[@*]

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

//BBB[not(@*)]

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

//BBB[@id='b1']

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

//BBB[@name='bbb']

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

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

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

6. count() :

//*[count(BBB)=2]

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

//*[count(*)=2]

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

//*[count(*)=3]

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

#html/xhtml/xml专栏