Dom Summary of JAXP

Document directory

• Dom development steps:

1. Introduction to JAXP and Dom

JAXP: Java API for XML programing

DOM: Document Object Method

Dom features:

(1) Put all XML documents into memory for parsing, which consumes memory;

(2) addition, deletion, modification, and query of XML;

<person><name>xiazdong</name><age>20</age></person>

Change to DOM tree:

Ii. DOM API

Common Dom classes include documentbuilderfactory, documentbuilder, document, node, nodelist, element, attribute, transformerfactory, transformer, domsource, and streamresult;

Dom development steps:

(1) Obtain documentbuilder through documentbuilderfactory;

(2) Parse XML through documentbuilder and obtain document (the root node of the document );

(3) operate through document;

(4) If the XML is modified, transformerfactory is required to create a transformer;

(5) Save it through transformer;

Common Operations of the documentbuilderfactory class include:

(1) documentbuilderfactory factory = documentbuilderfactory. newinstance ();

(2) documentbuilder builder = factory. newdocumentbuilder ();

The documentbuilder class includes:

(1) document = builder. parse (new file (""); // Parse XML and return the document Node

(2) document = builder. newdocument ();
// Create a document

The document class includes:

(1) nodelist list = getelementsbytagname ("name"); // the queue for obtaining the <Name> tag

(2) Element E = Document. createelement ("name ");
// Create a <Name> label and return

The nodelist class includes:

(1) node = nodelist. item (I); // obtain the I + 1 node of the node queue

(2) int length = nodelist. getlength (); // obtain the node queue length.

Node:

(1) string text = node. gettextcontent (); // obtain the node Value

(2) node. appendchild (node child); // Add a child node to the end of the node

(3) node. insertbefore (node child, node beforenode); // Add a child subnode before the node beforenode subnode

(4) nodelist list = node. getchildnodes ();
// Obtain all the subnodes of the node

(5) node parent = node. getparentnode (); // obtain the parent node of the node.

(6) node. removechild (node child); // remove the child node of the node

(7) node. settextcontent (string text); // set the node Value

(8) string name = node. getnodename (); // obtain the tag name.

Element: Besides the node class method

(1) element. setattribute ("name", "value ");
// Set tag attributes

(2) string value = element. getattribute ("name ");
// Obtain tag attributes

(3) element. removeattribute ("name") // remove tag attributes

Tranformerfactory contains:

(1) transformerfactory tfactory = transformerfactory. newinstance ();

(2) Transformer TF = tfactory. newtransformer ();

Transformer includes:

(1) TF. Transform (source, result );
// Output

Domsource includes:

(1) domsource source = new domsource (document );

Streamresult contains:

(1) streamresult result = new streamresult (New fileoutputstream ("1.xml "));

Iii. Dom crudxml:

<?xml version="1.0" encoding="UTF-8" standalone="no"?><personlist><person><name aaa="xxxx">xiazdong-1</name><age>20</age><salary>1000</salary></person><person><name>xiazdong-2</name><age>21</age><salary>2000</salary></person></personlist>

1. Create

private static void create(DocumentBuilder builder) throws Exception {Document document = builder.newDocument();Element root = document.createElement("person");Element name = document.createElement("name");name.setTextContent("xiazdong");Element age = document.createElement("age");age.setTextContent("20");root.appendChild(name);root.appendChild(age);document.appendChild(root);TransformerFactory tfactory = TransformerFactory.newInstance();Transformer tf = tfactory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream("output.xml")));}

private static void insert(Document document)throws Exception {Node person = document.getElementsByTagName("person").item(0);Node name = document.getElementsByTagName("name").item(0);Element tmp = document.createElement("tmpChild");tmp.setTextContent("xxx");person.insertBefore(tmp, name);TransformerFactory tfactory = TransformerFactory.newInstance();Transformer tf = tfactory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream("1.xml")));}

2. Read

private static void read(Document document) {Node node = document.getElementsByTagName("name").item(0);String name = node.getNodeName();String value = node.getTextContent();String attr = ((Element)node).getAttribute("aaa");System.out.println(name);System.out.println(value);System.out.println(attr);}

Application: traverse the entire XML document and Output

private static void readAll(Document document) {Node root = document.getElementsByTagName("personlist").item(0);read(root);}private static void read(Node node) {if(node instanceof Element)System.out.print("<"+node.getNodeName()+"></"+node.getNodeName()+">");NodeList list = node.getChildNodes();for(int i=0;i<list.getLength();i++){Node n = list.item(i);read(n);}}

3. Update

private static void update(Document document) throws Exception {Node node = document.getElementsByTagName("name").item(0);node.setTextContent("xiazdong");Element e = (Element)node;e.setAttribute("aaa", "111");TransformerFactory tfactory = TransformerFactory.newInstance();Transformer tf = tfactory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream("1.xml")));}

4. Delete

private static void delete(Document document) throws Exception{Node name = document.getElementsByTagName("name").item(0);name.getParentNode().removeChild(name);TransformerFactory tfactory = TransformerFactory.newInstance();Transformer tf = tfactory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream("1.xml")));}