XPath構文
XPathは、パス式を使用して、XMLドキュメント内のノードまたはノードセットを選択します。ノードは、パスまたはステップに従って選択されます。
XMLサンプルドキュメント
以下の例では、次のXMLドキュメントを使用します。
<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
<book>
<title lang="en">Harry Potter</title>
<price>29.99</price>
</book>
<book>
<title lang="en">Learning XML</title>
<price>39.95</price>
</book>
</bookstore>
ノードの選択
XPathは、パス式を使用してXMLドキュメント内のノードを選択します。ノードは、パスまたはステップに従って選択されます。最も有用なパス式を以下に示します。
| Expression | Description |
|---|---|
| nodename | Selects all nodes with the name "nodename" |
| / | 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 |
次の表に、いくつかのパス式と式の結果を示します。
| Path Expression | Result |
|---|---|
| bookstore | Selects all nodes with the name "bookstore" |
| /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 |
述語
述語は、特定のノードまたは特定の値を含むノードを見つけるために使用されます。
述語は常に角括弧で囲まれています。
以下の表に、述語を含むいくつかのパス式と式の結果を示します。
| Path Expression | Result |
|---|---|
| /bookstore/book[1] | Selects the first book element that is the child of the bookstore element.
Note: In IE 5,6,7,8,9 first node is[0], but according to W3C, it is [1]. To solve this problem in IE, set the SelectionLanguage to XPath: In JavaScript: xml.setProperty("SelectionLanguage","XPath"); |
| /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='en'] | Selects all the title elements that have a "lang" attribute with a value of "en" |
| /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 |
不明なノードの選択
XPathワイルドカードを使用して、不明なXMLノードを選択できます。
| Wildcard | Description |
|---|---|
| * | Matches any element node |
| @* | Matches any attribute node |
| node() | Matches any node of any kind |
次の表に、いくつかのパス式と式の結果を示します。
| Path Expression | Result |
|---|---|
| /bookstore/* | Selects all the child element nodes of the bookstore element |
| //* | Selects all elements in the document |
| //title[@*] | Selects all title elements which have at least one attribute of any kind |
複数のパスを選択する
|を使用して XPath式の演算子を使用すると、複数のパスを選択できます。
次の表に、いくつかのパス式と式の結果を示します。
| Path Expression | Result |
|---|---|
| //book/title | //book/price | Selects all the title AND price elements of all book elements |
| //title | //price | Selects all the title AND price elements in the document |
| /bookstore/book/title | //price | Selects all the title elements of the book element of the bookstore element AND all the price elements in the document |