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XML SAX

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XML Parser

DOM c nguyn mt XML file ri parse nthnh mt Tree c phn cp trong b nh, tcl mt node cha ca Document c nhng

nodes con i din cho comments,elements

,attributev text Trong khi SAX c mt XML file v trong

khi parse s generate nhng Events cho haykhi no n gp phi nhng XML thnh phn.

SAX khng to ra mt Tree no c, nn ccng dng ty thuc vo cch ta handle ccEvents t SAX

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NodeTypes - Named Constants

NodeType Named Constant

1 ELEMENT_NODE

2 ATTRIBUTE_NODE

3 TEXT_NODE

4 CDATA_SECTION_NODE

5 ENTITY_REFERENCE_NODE

6 ENTITY_NODE

7 PROCESSING_INSTRUCTION_NODE

8 COMMENT_NODE

9 DOCUMENT_NODE

10 DOCUMENT_TYPE_NODE

11 DOCUMENT_FRAGMENT_NODE

12 NOTATION_NODE

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SAX vs. DOM

TheDOM specificationdefinesatree-basedapproachtonavigatingan XML document.Inother words,aDOM parserprocesses XML dataandcreatesanobject-orientedhierarchicalrepresentationofthedocumentthatyoucannavigateatrun-time.

The SAX specificationdefinesanevent-basedapproach wherebyparsersscanthrough XML

data,callinghandlerfunctions whenevercertainpartsofthedocument (e.g.,textnodesorprocessinginstructions)arefound.

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SAX vs. DOM

SAX isastreaming interface applicationsreceiveinformationfrom XML documentsinacontinuousstream, withnobacktrackingornavigationallowed.

Thisappr

o

achmakes

SAXextremely

efficient,

han

d

ing

XML documentsofnearlyanysizeinlineartimeandnear-constantmemory,butitalsoplacesgreaterdemandsonthesoftwaredeveloper'sskills.

Tree-based interfaces,liketheDocumentObject Model(DOM),makeexactlytheoppositetrade-off:theyaremuchsimplerfordevelopers,butatthecostofsignificanttimeandcomputerresources.

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Events vs. Trees

TherearetwomajortypesofXML (or SGML) APIs:

Tree-based APIs Thesemapan XML documentintoaninternaltreestructure,thenallow anapplicationtonavigatethattree.

TheDocumentObject Model (DOM) workinggroupatthe

World-Wide Web Consortium (W3C)maintainsarecommendedtree-based APIfor XML and HTML documents,

andtherearemanysuch APIsfromothersources.

Event-based APIs Anevent-basedAPI,ontheotherhand,

repo

rtsparsingevents (suchasthestartand

end

o

felements)directlytotheapplicationthroughcallbacks,anddoesnot

usuallybuildaninternaltree.Theapplicationimplements

handlerstodeal withthedifferentevents,muchlikehandling

eventsinagraphicaluserinterface. SAX isthebestknown

exampleofsuchan API.