بناء جملة XPath
يستخدم XPath تعبيرات المسار لتحديد العقد أو مجموعات العقد في مستند XML. يتم تحديد العقدة باتباع المسار أو الخطوات.
مستند مثال XML
سنستخدم مستند XML التالي في الأمثلة أدناه.
<?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>
اختيار العقد
يستخدم XPath تعبيرات المسار لتحديد العقد في مستند XML. يتم تحديد العقدة باتباع المسار أو الخطوات. أكثر تعبيرات المسار فائدة مذكورة أدناه:
| 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 |
في الجدول أدناه قمنا بإدراج بعض تعبيرات المسار ونتائج التعبيرات:
| 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 |
المسند
تستخدم المسندات للعثور على عقدة معينة أو عقدة تحتوي على قيمة محددة.
دائمًا ما يتم تضمين المسندات بين قوسين مربعين.
في الجدول أدناه ، قمنا بإدراج بعض تعبيرات المسار مع المسندات ونتائج التعبيرات:
| 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 |
تحديد العقد غير المعروفة
يمكن استخدام أحرف البدل XPath لتحديد عُقد XML غير معروفة.
| Wildcard | Description |
|---|---|
| * | Matches any element node |
| @* | Matches any attribute node |
| node() | Matches any node of any kind |
في الجدول أدناه قمنا بإدراج بعض تعبيرات المسار ونتائج التعبيرات:
| 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 |
اختيار عدة مسارات
باستخدام | عامل تشغيل في تعبير XPath يمكنك تحديد عدة مسارات.
في الجدول أدناه قمنا بإدراج بعض تعبيرات المسار ونتائج التعبيرات:
| 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 |