Parsing XML files Java-web Dom Way

XML DOM tree structure:

DOM node

Each component in the Dom,xml document is a node .

This is what the DOM provides:

• The entire document is a document node
• Each XML element is an element node
• The text contained in the XML element is a text node
• Each XML attribute is an attribute node
• Comment is a comment node

Common node types

Node type	NodeType	Named Constant	return value of NodeName	return value of NodeValue
Element	1	Element_node	Element name	Null
Attr	2	Attribute_node	Property name	Property value
Text	3	Text_node	#text	Node name

Case:

Target: After parsing the XML file, the Java program can get all the data of the XML file

Thinking: How to preserve the structure information of XML after parsing

XML document:

Instance:

 PackageTest;/*** Case: Use DOM to parse XML file to get all the data of XML file*/ImportJavax.xml.parsers.DocumentBuilder;Importjavax.xml.parsers.DocumentBuilderFactory;Importorg.w3c.dom.Document;Importorg.w3c.dom.Element;ImportOrg.w3c.dom.NamedNodeMap;ImportOrg.w3c.dom.Node;Importorg.w3c.dom.NodeList; Public classDomdemo { Public Static voidMain (string[] args)throwsException {/**Step One: Create an Documentbuilderfactory Object * 1. Define the factory API, which enables applications to get the parser that generates the DOM object tree from an XML document. * 2. protected Documentbuilderfactory () * is used to block the instantiated protected construction method * 3.         Static Documentbuilderfactory newinstance () * Gets a new instance of Documentbuilderfactory. */documentbuilderfactory dbf=documentbuilderfactory.newinstance (); /**Step Two: Create a Documentbuilder Object * 1.protected documentbuilder () * Protected construction method * 2. Get the DOM document instance from the XML document.         With this class, the application programmer can get a Document from XML. */Documentbuilder DB=Dbf.newdocumentbuilder (); /**Step three: Load the Book.xml file into the current directory by using the parse method of the Documentbuilder object * 1.parse (file f) * resolves the contents of the given file to an XML document and returns a         The new DOM Document object. */Document Document= Db.parse ("books.xml"); /**Step four: Get a collection of all book Nodes * 1.getElementsByTagName (): Get all nodes with the same name through the names of the nodes, * because there is not only one node, so all the acquired nodes are stored in a node collection         。 */NodeList Booklist= document.getElementsByTagName ("book"); System.out.println ("A total" + booklist.getlength () + "book"); /**Step five: Traverse each book node * 1.Node item (int index) * Returns the index item in the collection.         * 2.NamedNodeMap getattributes () * Contains the NamedNodeMap of the property of this node (if it is Element); otherwise null. */                 for(inti = 0; I < booklist.getlength (); i++){                        //premise: Do not know how many ID attributes of the book nodeSystem.out.println ("===========" below begins to traverse the "+ (i+1) +" contents of this book =========== "); //get a book node with the Item methodNode book =Booklist.item (i); //gets all the property collections of the book NodeNamedNodeMap attrs =book.getattributes (); System.out.println ("First" + (i+1) + "book Total" + attrs.getlength () + "Properties"); //traversing the properties of a book             for(intj = 0; J < Attrs.getlength (); J + +){                //get a property of a book node by the Item methodNode attr =Attrs.item (j); //Get Property nameSystem.out.print ("Property name:" +attr.getnodename ()); //Get Property valueSystem.out.println ("--Attribute value:" +Attr.getnodevalue ()); }                        /*//premise: Already known that the book node has only one ID attribute//The book node is coerced type conversion to element type element ebook = (Element)            Booklist.item (i);            Get the property value by GetAttribute ("id") method String AttrValue = Ebook.getattribute ("id"); SYSTEM.OUT.PRINTLN ("id attribute value:" + attrValue);*/                        /**Step Six: Parse the child nodes of the book node * 1.NodeList getchildnodes () * contains NodeList for all child nodes of this node. */NodeList childNodes=book.getchildnodes (); //Traverse childnodes to get the node name and node value for each nodeSystem.out.println ("i+1" + "book Total" + childnodes.getlength () + "Child Node");  for(intk = 0; K < Childnodes.getlength (); k++){                                /*If the node type is not judged * traversing the child node of the book node will find 9 child nodes, but we have only written 4 child nodes * Output 5 #text nodes, this is the text type of node.                 * Because the space is also a child node, I will also be traversed out. * */                //distinguishes between node of type text and element type.                if(Childnodes.item (k). Getnodetype () = =Node.element_node) {                    //Gets the node name of the element type nodeSystem.out.print ("s" + (k+1) + "node is" + Childnodes.item (k). Getnodename () + ":"); /*when we use Childnodes.item (k). Getnodevalue () This method gets the node value of the node of type * element, which is returned empty, because he thinks * & Lt;name> Ice and Fire song </name> "Song of Ice and Fire" is a sub-node of <name>, so the value of the return <name> node is of course null, because it thinks that "Song of Ice and Fire" is a node and                     Not content.                     * We need to return the first child node of the <name> node, then return the value of the first child node, * or with gettextcontent () can also be resolved, it will get all the child nodes of the node value * */                    //System.out.println (Childnodes.item (k). Getfirstchild (). Getnodevalue ());System.out.println (Childnodes.item (k). Gettextcontent ()); }                        }                    }        }}

Operation Result:

There are 2 books , ===========. The following begins to traverse the contents of the 1th book =========== 1th book has 1 Properties property name: ID--property value:1 89==== ======= below begins to traverse the 2nd book's contents =========== 2nd book A total of 1 Property property name: ID--attribute value:22004 The 8th node is language: 中文版

Parsing XML files Java-web Dom Way