Java creating XML and the use of open source dom4j

Java

1 ImportJava.io.File;2 ImportJava.io.StringWriter;3 4 ImportJavax.xml.parsers.DocumentBuilder;5 Importjavax.xml.parsers.DocumentBuilderFactory;6 Importjavax.xml.parsers.ParserConfigurationException;7 ImportJavax.xml.transform.Transformer;8 Importjavax.xml.transform.TransformerConfigurationException;9 Importjavax.xml.transform.TransformerException;Ten Importjavax.xml.transform.TransformerFactory; One ImportJavax.xml.transform.dom.DOMSource; A ImportJavax.xml.transform.stream.StreamResult; -  - Importorg.w3c.dom.Document; the Importorg.w3c.dom.Element; -  -  -  Public classCreatxml { +  -      Public Static voidMain (string[] args) { +         Try { A              at              -             //DOM -Documentbuilderfactory factory =documentbuilderfactory.newinstance (); -Documentbuilder Builder =Factory.newdocumentbuilder (); -Document document =builder.newdocument (); -Element root = document.createelement ("Languages"); inRoot.setattribute ("Cat", "it"); -              toElement lan1 = document.createelement ("LAN"); +Lan1.setattribute ("id", "1"); -Element name1 = document.createelement ("name"); theName1.settextcontent ("Java"); *Element ide1 = document.createelement ("IDE"); $Ide1.settextcontent ("Eclipse");Panax Notoginseng Lan1.appendchild (name1); - Lan1.appendchild (ide1); the              +Element lan2 = document.createelement ("LAN"); ALan2.setattribute ("id", "2"); theElement name2 = document.createelement ("name"); +Name2.settextcontent ("Swift"); -Element Ide2 = document.createelement ("IDE"); $Ide2.settextcontent ("XCode"); $ Lan2.appendchild (name2); - Lan2.appendchild (ide2); -              theElement lan3 = document.createelement ("LAN"); -Lan3.setattribute ("id", "3");WuyiElement Name3 = document.createelement ("name"); theName3.settextcontent ("C #"); -Element ide3 = document.createelement ("IDE"); WuIde3.settextcontent ("Visual Studio"); - Lan3.appendchild (name3); About Lan3.appendchild (IDE3); $              - Root.appendchild (lan1); - Root.appendchild (lan2); - Root.appendchild (LAN3); A Document.appendchild (root); +              the             //------------- -              $Transformerfactory transformerfactory =transformerfactory.newinstance (); theTransformer Transformer =Transformerfactory.newtransformer (); theTransformer.setoutputproperty ("Encoding", "UTF-8"); the              theStringWriter writer =NewStringWriter (); -Transformer.transform (NewDomsource (document),NewStreamresult (writer)); in System.out.println (writer.tostring ()); the              theTransformer.transform (NewDomsource (document),NewStreamresult (NewFile ("Newxml.xml"))); About              the}Catch(parserconfigurationexception e) { the e.printstacktrace (); the}Catch(transformerconfigurationexception e) { + e.printstacktrace (); -}Catch(transformerexception e) { the e.printstacktrace ();Bayi         } the     } the  -}

Use of dom4j

1 Importorg.dom4j.Document;2 Importorg.dom4j.DocumentException;3 ImportOrg.dom4j.DocumentHelper;4 5 6  Public classTest {7 8      Public Static voidMain (string[] args) {9String xmlstring = "<root><people>ACELY</people></root>";Ten          One         Try { A              -              -              theDocument document =Documenthelper.parsetext (xmlstring); -              - System.out.println (Document.asxml ()); -              +              -              +}Catch(documentexception e) { A e.printstacktrace (); at         } -     } -  -}

DOM4J Working with Documents

Parsing XML

One of the first things you'll probably want to does is to parse an XML document of some kind. This is an easy-to-do in dom4j. The following code demonstrates.

Import Java.net.url;import org.dom4j.document;import org.dom4j.documentexception;import org.dom4j.io.SAXReader; public class Foo {public    Document parse (url url) throws documentexception {        Saxreader reader = new Saxreader (); 
   document Document = reader.read (URL);        return document;    }}

Using iterators

A document can be navigated using a variety of methods and return standard Java iterators. For example

    public void Bar (document document) throws Documentexception {        Element root = Document.getrootelement ();        Iterate through child elements of the root for        (Iterator i = Root.elementiterator (); I.hasnext ();) {            Element element = (Element) i.next ();            Do something        }        //Iterate through child elements of the root with element name ' foo ' for        (Iterator i = Root.el Ementiterator ("foo"); I.hasnext (); {            element foo = (element) i.next ();            Do something        }        //Iterate through attributes of the root for         (Iterator i = Root.attributeiterator (); i.hasn Ext (); ) {            Attribute Attribute = (Attribute) i.next ();            Do something        }     }

Powerful Navigation with XPath

In dom4j XPath Expressions can is evaluated on the Document or on any Node in the tree (such as Attribute, Elemen T or ProcessingInstruction). This is allows complex navigation throughout the document with a single line of code. For example.

    public void Bar (document document) {        List list = Document.selectnodes ("//foo/bar");        Node node = document.selectsinglenode ("//foo/bar/author");        String name = node.valueof ("@name");    }

For example if your wish to find all the hypertext links in a XHTML document the following code would do the trick.

    public void FindLinks (document document) throws Documentexception {        List list = Document.selectnodes ("//a/@href"); C8/>for (Iterator iter = List.iterator (); Iter.hasnext ();) {            Attribute Attribute = (Attribute) iter.next ();            String URL = attribute.getvalue ();        }    }

If you need any help learning the XPath language we highly recommend the Zvon tutorial which allows your to learn by Exampl E.

Fast Looping

If you ever has to walk a large XML document tree then for performance we recommend you use the fast looping method which Avoids the cost of creating a Iterator object for Each loop. For example

    public void Treewalk (document document) {        Treewalk (document.getrootelement ());    }    public void Treewalk (element Element) {        for (int i = 0, size = Element.nodecount (); i < size; i++) {            Node nod E = Element.node (i);            if (node instanceof Element) {                Treewalk (Element) node);            }            else {                //do Something ...}}}    

Creating a new XML document

Often in dom4j you'll need to create a new document from scratch. Here's an example of doing.

Import Org.dom4j.document;import Org.dom4j.documenthelper;import Org.dom4j.element;public class Foo {public    Document CreateDocument () {        Document document = Documenthelper.createdocument ();        Element root = document.addelement ("root");        Element Author1 = root.addelement ("author")            . AddAttribute ("name", "James")            . AddAttribute ("Location", "UK") C7/>.addtext ("James Strachan");                Element Author2 = root.addelement ("author")            . AddAttribute ("name", "Bob")            . AddAttribute ("Location", "US") 
   .addtext ("Bob mcwhirter");        return document;    }}

Writing a document to a file

A quick and easy-to-write a Document (or any Node) to a Writer is via the Write () method.

  FileWriter out = new FileWriter ("Foo.xml");  document.write (out);

If you want to is able to change the format of the output, such as pretty printing or a compact format, or you want to be Able to work with Writer objects or OutputStream objects as the destination and then you can use the XMLWriter class.

Import Org.dom4j.document;import Org.dom4j.io.outputformat;import Org.dom4j.io.xmlwriter;public class Foo {    public void Write (document document) throws IOException {        //lets write to a file        XMLWriter writer = new XMLWriter (            new FileWriter ("Output.xml")        );        Writer.write (document);        Writer.close ();        Pretty print the document to System.out        outputformat format = Outputformat.createprettyprint ();        writer = new XMLWriter (system.out, format);        Writer.write (document);        Compact format to system.out        format = Outputformat.createcompactformat ();        writer = new XMLWriter (system.out, format);        Writer.write (document);}    }

converting to and from Strings

If you had a reference to a Document or any other Node such as an Attribute or Element, you can turn it into the default XML text via the Asxml () method.

        Document document = ...;        String text = Document.asxml ();

If you had some XML as a String you can parse it back into a Document again using the helper method Documenthelper.parset EXT ()

        String Text = "<person> <name>James</name> </person>";        Document document = Documenthelper.parsetext (text);

Styling a Document with XSLT

Applying XSLT on a Document are quite straightforward using the JAXP API from Sun. This allows the against any XSLT engine such as Xalan or SAXON. Here's an example of using JAXP to create a transformer and then applying it to a Document.

Import Javax.xml.transform.transformer;import Javax.xml.transform.transformerfactory;import org.dom4j.Document; Import Org.dom4j.io.documentresult;import Org.dom4j.io.documentsource;public class Foo {public    Document Styledocument (        document document,         String stylesheet    ) throws Exception {        //load the transformer using JAXP        Transformerfactory factory = Transformerfactory.newinstance ();        Transformer Transformer = Factory.newtransformer (             new Streamsource (stylesheet)         );        Now lets style the given document        DocumentSource Source = new DocumentSource (document);        Documentresult result = new Documentresult ();        Transformer.transform (source, result);        Return the transformed document        document Transformeddoc = Result.getdocument ();        return transformeddoc;}    }

Java creating XML and the use of open source dom4j