XML-dom parsing XML

1. How XML is parsed using dom

• Based on the DOM (Document Object Model) parsing method, the entire XML file is loaded into the memory and converted into a DOM tree, therefore, applications can randomly access any data in the DOM tree;
• Advantages: high flexibility and fast speed;
• Disadvantage: resource consumption is high;

2. Elements vs nodes (nodes contain elements)

• Nodes include element nodes, attribute nodes, and text nodes.

  <! -- Students. xml -->
  <? XML version = "1.0" encoding = "UTF-8"?> <Students> <student> <name ID = "001" xx = "Haha"> Michael Zhang </Name> <sex> male </sex> <age> 20 </age> </student> <name ID = "002"> Li Si </Name> <sex> female </sex> <age> 21 </age> </student> </students> // element node: student, name, sex, age // attribute node: ID, AA // text node: James, male, 20

   

• The element must be a node, but the node is not necessarily an element.

3. XML parsing example using dom

• Example

  Import javax. XML. parsers. documentbuilder; import javax. XML. parsers. documentbuilderfactory; import Org. w3C. dom. document; import Org. w3C. dom. element; import Org. w3C. dom. namednodemap; import Org. w3C. dom. node; import Org. w3C. dom. nodelist; public class dom02 {public static void printnodeattr (node) {namednodemap = node. getattributes (); For (INT I = 0; I <namednodemap. getlength (); I ++) {// traverses the attribute node attrnode = namednodemap. item (I); system. out. println (attrnode. getnodename () + ":" + attrnode. getfirstchild (). getnodevalue () ;}} public static void main (string [] ARGs) {documentbuilderfactory factory = documentbuilderfactory. newinstance (); // obtain the factory instance try {documentbuilder builder = factory. newdocumentbuilder (); // Parse XML document DOC = builder through builder. parse ("src/students. XML "); // obtain the document nodelist = Doc. getelementsbytagname ("Students"); // obtain the node element = (element) nodelist by Tag name. item (0); nodelist studentsnodelist = element. getelementsbytagname ("student"); // obtain the node for (INT I = 0; I <studentsnodelist. getlength (); I ++) {Element E = (element) studentsnodelist. item (I); // element is a subclass of node. It has more functions than node. out. println ("name:" + E. getelementsbytagname ("name "). item (0 ). getfirstchild (). getnodevalue (); printnodeattr (E. getelementsbytagname ("name "). item (0); system. out. println ("Gender:" + E. getelementsbytagname ("sex "). item (0 ). getfirstchild (). getnodevalue (); system. out. println ("Age:" + E. getelementsbytagname ("Age "). item (0 ). getfirstchild (). getnodevalue (); system. out. println ("====================") ;}} catch (exception e) {// todo auto-generated Catch Block E. printstacktrace ();}}}

   

 

XML-dom parsing XML