Parsing XML using XPath in Java

XPath is a language that looks for information in an XML document. XPath is used to navigate through elements and attributes in an XML document. Its return value may be a node, a node collection, text, and a mixture of nodes and text.
Before you learn this document, you should have a certain understanding of XML nodes, elements, attributes, text, processing instructions, annotations, root nodes, namespaces, and node relationships, as well as an understanding of XPath.
XML Learning Address:http://www.runoob.com/xml/xml-tutorial.html
XPath basic Syntax learning address:http://www.runoob.com/xpath/xpath-tutorial.html
XPath Official document:Https://yunpan.cn/cvc4tEIGy5EvS access password 9d16
This article focuses on: Using XPath operations on XML operations in Java.
1) How to use XPath technology first in dom4j
Imports the supported jar packages for XPath. Jaxen-1.1-beta-6.jar (first import dom4j package, dom4j:http://www.dom4j.org/dom4j-1.6.1/).

After the Guide package:

If you do not know how to guide the package please refer to my previous blog:java Get XML node summary read XML document node
2) using the XPath method in Java, there are two main points:
List<node> selectnodes ("XPath expression"); Querying multiple Node objects
Node selectSingleNode ("XPath expression"); Querying a Node object
Here's an example of how to use it.

First, selectnodes use method:

1  PackageCom.vastsum.demo;2 3 ImportJava.io.File;4 ImportJava.io.FileOutputStream;5 Importjava.util.List;6 7 Importorg.dom4j.Document;8 Importorg.dom4j.Element;9 ImportOrg.dom4j.Node;Ten ImportOrg.dom4j.io.OutputFormat; One ImportOrg.dom4j.io.SAXReader; A ImportOrg.dom4j.io.XMLWriter; -  - /** the  *  -  * @authorshutu008 - How to use *selectnode -  */ +  Public classXpathdemo { -  +      Public Static voidMain (string[] args)throwsException { A  atDocument doc =NewSaxreader (). Read (NewFile ("./src/contact.xml"))); -          -         /** -          * @paramXPath represents the XPath syntax variable -          */ -String xpath= ""; in          -         /** to * 1. /absolute path represents the beginning of the root position of the XML or child element (a hierarchy) +          */ -XPath = "/contactlist"; theXPath = "/contactlist/contact"; *          $         /**Panax Notoginseng * 2.//The relative path represents a selection element that is not divided into any hierarchy.  -          */ theXPath = "//contact/name"; +XPath = "//name"; A          the         /** + * 3. * Wildcard character means matching all elements -          */ $XPath = "/contactlist/*";//all sub-labels under the root tag contactlist $XPath = "/contactlist//*";//all tags under the root tag contactlist (no hierarchy) -          -         /** the * 4. [] condition indicates which element is selected under what conditions -          */Wuyi         //Contact label with id attribute theXPath = "//contact[@id]"; -         //the second contact label WuXPath = "//contact[2]"; -         //Select the last contact label AboutXPath = "//contact[last ()]"; $          -         /** - * 5. The @ attribute indicates the Select attribute node -          */ AXPath = "//@id";//Select the id attribute node object, which returns the attribute object +XPath = "//contact[not (@id)]";//Select the contact label node that does not contain an id attribute theXPath = "//contact[@id = ' 002 ']";//Select the contact label with an id attribute value of 002 -XPath = "//contact[@id = ' 001 ' and @name = ' Eric ']";//Select the id attribute value of 001, and the Name property is Eric's contact label $          the         /** the *6. Text () indicates selection of textual content the          */ the         //Select the text content under the name label to return to the TextBox object -XPath = "//name/text ()"; inXPath = "//contact/name[text () = ' Zhang San ']";//Select the name tag named Zhang San the          the          Aboutlist<node> list =Doc.selectnodes (XPath); the          for(Node node:list) { the System.out.println (node); the         } +      -         //write out an XML file the         //Output PositionBayiFileOutputStream out =NewFileOutputStream ("D:/contact.xml"); the          the         //Specify Format -OutputFormat format =outputformat.createprettyprint (); -Format.setencoding ("Utf-8"); theXMLWriter writer =NewXMLWriter (Out,format); the          the         //Write Content the Writer.write (DOC); -          the         //Close Resource the writer.close (); the         94     } the      the  the}

Second, the use of selectSingleNode method

1  PackageCom.vastsum.demo;2 3 ImportJava.io.File;4 ImportJava.util.Iterator;5 6 ImportOrg.dom4j.Attribute;7 Importorg.dom4j.Document;8 Importorg.dom4j.Element;9 ImportOrg.dom4j.io.SAXReader;Ten  One /** A  *  -  * @authorshutu008 - Use of *selectsinglenode the  */ -   Public classxpathdemo1{ -       Public Static voidMain (string[] args)throwsexception{ -          //read the XML file to get the Document object +Saxreader Saxreader =NewSaxreader ();  -Document doc = Saxreader.read (NewFile ("./src/contact.xml"))); +          A         //get a node using XPath atString XPath = ""; -          -         //for the Contact element id= "001" node, the Operation -XPath = "//contact[@id = ' 001 ']"; -Element Contactelem =(Element) Doc.selectsinglenode (XPath); -          in         //set the attribute value for this node -Contactelem.addattribute ("name", "001"); to          +         //outputs all attribute values for this node -          for(Iterator it =contactelem.attributeiterator (); It.hasnext ();) { theAttribute conattr =(Attribute) It.next (); *String Contxt =Conattr.getvalue (); $String Conattrname =conattr.getname ();Panax NotoginsengSystem.out.println (conattrname+ "=" +contxt); -         } the          +      } A}

Note: The following is an XML file of the operation

1<?xml version= "1.0" encoding= "UTF-8"?>2<contactlist id= "0" >3<contact id= "001"class= "Style" Name= "Lisi" >4<name> Zhang San </name>5<age>20</age>6<phone>134222223333</phone>7<email>[email protected]</email>8<qq>432221111</qq>9</contact>Ten<contact id= "002" > One<name> John Doe </name> A<age>20</age> -<phone>134222225555</phone> -<email>[email protected]</email> the<qq>432222222</qq> -</contact> -<contactTwo> -<name> Harry </name> +<age>32</age> -<phone>465431341</phone> +<emali>[email protected]</emali> A<qq>46164694</qq> at</contactTwo> -<test> Testing </test> -<test> Other uses </test> -</contactList>

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Parsing XML using XPath in Java