XML-based JAXP Parsing

XML-based JAXP Parsing

JAXP: a set of xml parsing developed by sun

It consists of javax. xml. parsers, org. w3c. dom, org. xml. sax, and its sub-packages.

JAXP has two Resolution Methods:

I. dom parsing: Read documents into memory to produce Document objects

Ii. sax parsing: read from the top down and read a row to process a row

Dom advantages: convenient for document CRUD

Disadvantage: High memory consumption

Advantages of sax: Small memory consumption, fast resolution, and suitable for reading documents

Disadvantage: CUD is inconvenient

Instance xml document

 
 <书架>
  <书>
   <书名 id="1234">
    
. Net
   
   <作者>
    
Wht
   
  
  <书>
   <书名>
    
JavaEE
   
   <作者>
    
Www
   
  
 

Dom parsing steps

Create the dom factory DocumentBuilderFactory to get the dom parser DocumentBuilder to read the xml Document and get the Document

Package Jaxp. dom; import javax. xml. parsers. documentBuilder; import javax. xml. parsers. documentBuilderFactory; import javax. xml. transform. transformer; import javax. xml. transform. transformerFactory; import javax. xml. transform. dom. DOMSource; import javax. xml. transform. stream. streamResult; import org. junit. test; import org. w3c. dom. document; import org. w3c. dom. element; import org. w3c. dom. node; import org. w3c. dom. nodeList; public class Dom {// read a specified tag in the document @ Testpublic void read1 () throws Exception {// 1. Create the dom factory DocumentBuilderFactory factory = DocumentBuilderFactory. newInstance (); // 2. Create the parser DocumentBuilder builder = factory. newDocumentBuilder (); // 3. Read the xml file and generate the Document Object Document document = builder. parse ("src/book. xml "); Node node = document. getElementsByTagName (" "). item (0); System. out. println (node. getNodeName ();} // read the tag @ Testpublic void read2 () throws Exception {// 1. Create the dom factory DocumentBuilderFactory factory = DocumentBuilderFactory. newInstance (); // 2. Create the parser DocumentBuilder builder = factory. newDocumentBuilder (); // 3. Read the xml file and generate the Document Object Document document = builder. parse ("src/book. xml "); Node root = document. getElementsByTagName ("bookshelf "). item (0); list (root);} private void list (Node node) {// TODO Auto-generated method stubSystem. out. println (node. getNodeName (); NodeList nodes = node. getChildNodes (); for (int I = 0; I
 
  

  
Create a sax factory SAXParserFactory. Get the sax Parser SAXParser. Get the reader XMLReader. Set the content processing processor reader. setContentHandler () to read the xml document.
  
Package Jaxp. sax; import java. io. IOException; import javax. xml. parsers. parserConfigurationException; import javax. xml. parsers. SAXParser; import javax. xml. parsers. SAXParserFactory; import org. xml. sax. attributes; import org. xml. sax. contentHandler; import org. xml. sax. locator; import org. xml. sax. SAXException; import org. xml. sax. XMLReader; public class Demo {public static void main (String [] args) throws ParserConfigurationException, SAXException, IOException {// 1. Create a sax factory SAXParserFactory factory = SAXParserFactory. newInstance (); // 2. Get the parser SAXParser saxParser = factory. newSAXParser (); // 3. Obtain the reader XMLReader reader = saxParser. getXMLReader (); // 4. Set the content processor reader. setContentHandler (new XMLHandler (); // 5. Read the xml document reader. parse ("src/book. xml ") ;}} class XMLHandler implements ContentHandler {@ Overridepublic void startElement (String uri, String localName, String qName, Attributes atts) throws SAXException {// TODO Auto-generated method stubSystem. out. println ("<" + qName + ">"); for (int I = 0; I ") ;}@ Overridepublic void characters (char [] ch, int start, int length) throws SAXException {// TODO Auto-generated method stubSystem. out. println (new String (ch, start, length) ;}@ Overridepublic void setDocumentLocator (Locator locator) {// TODO Auto-generated method stub} @ Overridepublic void startDocument () throws SAXException {// TODO Auto-generated method stub} @ Overridepublic void endDocument () throws SAXException {// TODO Auto-generated method stub} @ Overridepublic void startPrefixMapping (String prefix, string uri) throws SAXException {// TODO Auto-generated method stub} @ Overridepublic void endPrefixMapping (String prefix) throws SAXException {// TODO Auto-generated method stub} @ Overridepublic void ignorableWhitespace (char [] ch, int start, int length) throws SAXException {// TODO Auto-generated method stub} @ Overridepublic void processingInstruction (String target, String data) throws SAXException {// TODO Auto-generated method stub} @ Overridepublic void skippedEntity (String name) throws SAXException {// TODO Auto-generated method stub }}
  
Sun provides DefaultHandler
  

  
Package Jaxp. sax; import java. io. IOException; import javax. xml. parsers. parserConfigurationException; import javax. xml. parsers. SAXParser; import javax. xml. parsers. SAXParserFactory; import org. xml. sax. attributes; import org. xml. sax. contentHandler; import org. xml. sax. locator; import org. xml. sax. SAXException; import org. xml. sax. XMLReader; import org. xml. sax. helpers. defaultHandler; public class Demo2 {public static void main (String [] args) throws ParserConfigurationException, SAXException, IOException {// 1. Create a sax factory SAXParserFactory factory = SAXParserFactory. newInstance (); // 2. Get the parser SAXParser saxParser = factory. newSAXParser (); // 3. Obtain the reader XMLReader reader = saxParser. getXMLReader (); // 4. Set the content processor reader. setContentHandler (new TagValue (); // 5. Read the xml document reader. parse ("src/book. xml ") ;}} // obtain the second author's name class TagValue extends DefaultHandler {private String currentTag; private int currentNum; private int needTagNum = 2; @ Overridepublic void startElement (String uri, String localName, String qName, Attributes attributes) throws SAXException {currentTag = qName; if (currentTag. equals ("author") {currentNum ++ ;}@ Overridepublic void characters (char [] ch, int start, int length) throws SAXException {if ("author ". equals (currentTag) & export tNum = needTagNum) {System. out. println (new String (ch, start, length) ;}@ Overridepublic void endElement (String uri, String localName, String qName) throws SAXException {currentTag = null ;}}