《XMl的SAX读取方法》PPT课件.ppt

1,第5章SAX,TheSimpleAPIforXML,2,在应用程序中使用XML文档,3,SAX的特点,通过触发事件，顺序访问元素已经分析过的数据，不能再返回处理内存占用量较少，基本固定事实标准，而非W3C标准最初版本SAX1.0当前版本SAX2.0,4,SAX语法分析体系结构,SAXParserFactory,SAXParser,XML,SAXReader,ContentHandler,ErrorHandler,DTDHandler,EntityHandler,5,获取SAX解析器,javax.xml.parsers.SAXParserFactory;javax.xml.parsers.SAXParser;javax.xml.parsers.ParserConfigurationException;/gettheparserSAXParserFactoryfactory=SAXParserFactory.newInstance();SAXParsersaxParser=factory.newSAXParser();/parsethedocumentsaxParser.parse(newFile(argv0),handler);,6,将某个handler传送给解析器,NotethataneventhandlerhastobepassedtotheSAXparser.Thismustimplementtheinterfaceorg.xml.sax.ContentHandler;Easiertoextendtheadapterorg.xml.sax.helpers.DefaultHandler,7,OverridingHandlermethods,MostimportantmethodstooverridevoidstartDocument()CalledoncewhendocumentparsingbeginsvoidendDocument()CalledoncewhenparsingendsvoidstartElement(.)CalledeachtimeanelementbegintagisencounteredvoidendElement(.)Calledeachtimeanelementendtagisencounteredvoidcharacters(.)CalledrandomlybetweenstartElementandendElementcallstoaccumulatedcharacterdata,8,startElement,publicvoidstartElement(StringnamespaceURI,/ifnamespaceassocStringsName,/nonqualifiednameStringqName,/qualifiednameAttributesattrs)/listofattributesAttributeinfoisobtainedbyqueryingAttributesobjects.,9,Characters,publicvoidcharacters(charbuf,/bufferofcharsaccumulatedintoffset,/beginelementofcharsintlen)/numberofcharsNote,charactersmaybecalledmorethanoncebetweenbegintag/endtagAlso,mixed-contentelementsrequirecarefulhandling,10,SAX应用示例(1/9),作为输入的XML文档KilpelinenPekkaMttnenMattiMttnenMaijaRmppnenMaija,11,SAX应用示例1(2.1/9),要求的输出如下：PekkaKilpelinen(1234)MattiMttnen(5678)MaijaMttnen(9012)MaijaRmppnen(3456),12,SAX应用示例1(2.2/9),事件驱动的处理策略从元素person开始,记录idnum(e.g.,1234)记录各个last与first元素的开始与结束，以便存储其元素内容(e.g.,“Kilpelinen”和Pekka)每一个person元素结束时,输出与该元素有关的数据,13,SAX应用示例1(3/9),Application:Firstimportrelevantinterfaces,14,SAX应用示例1(4/9),Implementrelevantcall-backmethods:publicclassSAXDBAppextendsDefaultHandler/Flagstorememberelementcontext:privatebooleanInFirst=false,InLast=false;/Storageforelementcontentsand/attributevalues:privateStringFirstName,LastName,IdNum;,15,SAX应用示例1(5/9),Call-backmethods:recordthestartoffirstandlastelements,andtheidnumattributeofaperson:publicvoidstartElement(StringnsURI,StringlocalName,StringrawName,Attributesatts)if(rawName.equals(person)IdNum=atts.getValue(idnum);if(rawName.equals(first)InFirst=true;if(rawName.equals(last)InLast=true;/startElement,16,SAX应用示例1(6/9),Call-backmethodscontinue:Recordthetextcontentofelementsfirstandlast:publicvoidcharacters(charbuf,intstart,intlength)if(InFirst)FirstName=newString(buf,start,length);if(InLast)LastName=newString(buf,start,length);/characters,17,SAX应用示例1(7/9),Attheendofperson,outputthecollecteddata:publicvoidendElement(StringnsURI,StringlocalName,StringqName)if(qName.equals(person)System.out.println(FirstName+LastName+(+IdNum+);/Updatethecontextflags:if(qName.equals(first)InFirst=false;/(andthesameforlastandInLast),18,SAX应用示例1(8/9),Applicationmainmethod:publicstaticvoidmain(Stringargs)throwsException/InstantiateanXMLReader(fromJAXP/SAXParserFactory):SAXParserFactoryspf=SAXParserFactory.newInstance();trySAXParsersaxParser=spf.newSAXParser();XMLReaderxmlReader=saxParser.getXMLReader();,19,SAX应用示例1(9/9),Mainmethodcontinues:/Instantiateandpassanew/ContentHandlertoxmlReader:ContentHandlerhandler=newSAXDBApp();xmlReader.setContentHandler(handler);for(inti=0;iargs.length;i+)xmlReader.parse(argsi);catch(Exceptione)System.err.println(e.getMessage();System.exit(1);/main,20,SAX应用示例2,21,SampleXMLDocument,taatttctcccattttgtaggttatcacttcactctgttgactttcttttgtaatgcaactaaatccaggcgaagcatttcagcttaaccccgagacttttg,DocumentcontainstwosequencesofDNA.,22,StartDocumentStartElement:DASDNAStartElement:SEQUENCEStartElement:DNACharacters:taatttctcccattttgtaggttatcacttcactctgttgactttcttttgCharacters:EndElement:DNAEndElement:SEQUENCEStartElement:SEQUENCEStartElement:DNACharacters:taatgcaactaaatccaggcgaagcatttcagcttaaccccgagacttttgCharacters:EndElement:DNAEndElement:SEQUENCEEndElement:DASDNAEndDocument,SampleOutput,23,packagecom.oreilly.bioxml.sax;importorg.xml.sax.Attributes;importorg.xml.sax.ContentHandler;importorg.xml.sax.Locator;importorg.xml.sax.SAXException;importorg.xml.sax.XMLReader;importorg.xml.sax.helpers.XMLReaderFactory;importjava.io.IOException;/*BasicSAXExample.*IllustratesbasicimplementationoftheSAXContentHandler.*/publicclassSAXBasicimplementsContentHandlerpublicvoidstartDocument()throwsSAXExceptionSystem.out.println(StartDocument);,24,publicvoidcharacters(charch,intstart,intlength)throwsSAXExceptionStringstr=newString(ch,start,length);System.out.println(Characters:+str);publicvoidendDocument()throwsSAXExceptionSystem.out.println(EndDocument);publicvoidendElement(StringnamespaceURI,StringlocalName,StringqName)throwsSAXExceptionSystem.out.println(EndElement:+localName);publicvoidendPrefixMapping(Stringprefix)throwsSAXException/No-op,25,publicvoidignorableWhitespace(charch,intstart,intlength)throwsSAXException/No-oppublicvoidprocessingInstruction(java.lang.Stringtarget,java.lang.Stringdata)throwsSAXException/No-oppublicvoidsetDocumentLocator(Locatorlocator)/No-oppublicvoidskippedEntity(Stringname)throwsSAXException/No-oppublicvoidstartElement(StringnamespaceURI,StringlocalName,StringqName,Attributesatts)throwsSAXExceptionSystem.out.println(StartElement:+localName);,26,publicvoidstartPrefixMapping(Stringprefix,Stringuri)throwsSAXException/No-op/*PrintsCommandLineUsage*/privatestaticvoidprintUsage()System.out.println(usage:SAXBasicxml