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XPath Syntax
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XML Weg-Sprache verwendet eine feststellende Darstellung anstatt ein Verfahrens. Jeder Ausdruck entwickelte sich durch diese Darstellung beschreibt die Arten von Nullpunkten zum Gleichen, das auf dem hierarchischen Verh�ltnis zwischen den Nullpunkten basierte. Z.B. finden die Ausdruck �Buch-/Autoren� Mittel das Autor Element enthalten im Buchelement.
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| XML Beispiel
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| Ein XML Dokument wird unten gegeben.
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<?xml version="1.0" encoding="ISO-8859-1"?><bookstore><book>
<title lang="eng">Harry Potter</title>
<price>29.99</price>
</book><book>
<title lang="eng">Learning XML</title>
<price>39.95</price>
</book></bookstore>
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| Vorw�hlen von Nullpunkten
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Nullpunkte XPath Gebrauch-Wegausdr�cke vorw�hlen. Der Nullpunkt wird vorgew�hlt, indem man einem Weg folgt. Die n�tzlichsten Wegausdr�cke sind: -
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| Expression |
Description |
| nodename |
Selects all child nodes of the node |
| / |
Selects from the root node |
| // |
Selects nodes in the document from the current node
that match the selection no matter where they are |
| . |
Selects the current node |
| .. |
Selects the parent of the current node |
| @ |
Selects attributes |
| Beispiel
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| Die Tabelle, die unten haben wir gegeben wird, einige Wegausdr�cke und das Resultat der Ausdr�cke verzeichnet:
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| Path Expression |
Result |
| bookstore |
Selects all the child nodes of the bookstore element |
| /bookstore |
Selects the root element bookstore
Note: If the path starts with a slash ( / ) it always
represents an absolute path to an element! |
| bookstore/book |
Selects all book elements that are children of
bookstore |
| //book |
Selects all book elements no matter where they are in
the document |
| bookstore//book |
Selects all book elements that are descendant of the
bookstore element, no matter where they are under the bookstore element |
| //@lang |
Selects all attributes that are named lang |
| Pr�dikate
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Pr�dikate werden verwendet, um einen spezifischen Nullpunkt zu finden, der einen Wert enth�lt. Pr�dikate werden immer in den eckigen Klammern eingebettet.
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Example
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Table given below we have listed some path expressions with predicates and
the result of the expressions:
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| Path Expression |
Result |
| /bookstore/book[1] |
Selects the first book element that is the child of the
bookstore element |
| /bookstore/book[last()] |
Selects the last book element that is the child of the
bookstore element |
| /bookstore/book[last()-1] |
Selects the last but one book element that is the child
of the bookstore element |
| /bookstore/book[position()<3] |
Selects the first two book elements that are children
of the bookstore element |
| //title[@lang] |
Selects all the title elements that have an attribute
named lang |
| //title[@lang='eng'] |
Selects all the title elements that have an attribute
named lang with a value of 'eng' |
| /bookstore/book[price>35.00] |
Selects all the book elements of the bookstore element
that have a price element with a value greater than 35.00 |
| /bookstore/book[price>35.00]/title |
Selects all the title elements of the book elements of
the bookstore element that have a price element with a value greater
than 35.00 |
| Wie wir unbekannte Nullpunkte vorw�hlend?
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| Wildcards k�nnen benutzt werden, um unbekannte XML Elemente vorzuw�hlen.
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| Wildcard |
Description |
| * |
Matches any element node |
| @* |
Matches any attribute node |
| node() |
Matches any node of any kind |
| Beispiel
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| Die Tabelle, die unten haben wir gegeben wird, einige Wegausdr�cke und das Resultat der Ausdr�cke verzeichnet:
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| Path Expression |
Result |
| /bookstore/* |
Selects all the child nodes of the bookstore element |
| //* |
Selects all elements in the document |
| //title[@*] |
Selects all title elements which have any attribute |
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