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Sintaxe de XPath
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A l�ngua do trajeto de XML usa uma nota��o declarativa melhor que processual. Cada express�o tornou-se por esta nota��o descreve os tipos de n�s ao f�sforo baseado no relacionamento hier�rquico entre os n�s. Por exemplo, autor da express�o do �os meios livro/� encontram o elemento do autor contido no elemento do livro.
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| Exemplo de XML
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| Um original de XML � dado abaixo.
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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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| Selecionando n�s
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Para selecionar express�es do trajeto dos usos de XPath dos n�s. O n� � selecionado seguindo um trajeto. As express�es as mais �teis do trajeto s�o: -
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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 |
| Exemplo
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| Tabela dada abaixo n�s alistamos algumas express�es do trajeto e o resultado das express�es:
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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 |
| Predicados
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Os predicados s�o usados encontrar um n� espec�fico que contenha um valor. Os predicados s�o encaixados sempre nos suportes quadrados.
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| Exemplo
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Tabela dada abaixo n�s alistamos algumas express�es do trajeto com predicados e o resultado das express�es:
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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 |
| Como n�s que selecionamos n�s desconhecidos?
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| Os Wildcards podem ser usados selecionar elementos desconhecidos de XML.
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| Wildcard |
Description |
| * |
Matches any element node |
| @* |
Matches any attribute node |
| node() |
Matches any node of any kind |
| Exemplo
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| Tabela dada abaixo n�s alistamos algumas express�es do trajeto e o resultado das express�es:
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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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