Re: Singleton a dedicnost

[Martin Kuba]

[EMAIL PROTECTED] wrote:

Hi all

Mam takyto kod:

Chcem riesit pomocou singletona jedinu instanciu class MojaApp, pricom chcem aby ten singleton bol rieseny v predkovy KernelApp ako mam vlastne vytvorit MojaApp, kedze singleton v KernelApp vola new KernelApp a nie new MojaApp?

Na to se pouziva tzv. Abstract Factory Pattern, popis viz Google,

SUNove to v JDK pouzivaji celkem casto, viz napr. tridy

javax.xml.transform.TransformerFactory
javax.xml.parsers.SAXParserFactory

a delaji to tak, ze konkretni instanci factory vybiraji podle systemove
property stejneho jmena, tedy "javax.xml.transform.TransformerFactory"
pripadne "javax.xml.parsers.SAXParserFactory".

Takze kdyz pak chci spusti svuj program s jinym SAX parserem
a XSLT procesorem nez josu v JDK, spustim program s treba

java \

MujProgram

a tridy SAXParserFactory a TransformerFactory si nainstancuji
tyhle specifikovane tridy, a pri volani newInstance() pak
vraci prislusne instance.

Pro singleton muzete udelat totez, jenom misto newInstance()
budete mit getInstance().

Makub
--
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Supercomputing Center Brno             Martin Kuba
Institute of Computer Science    email: [EMAIL PROTECTED]
Masaryk University             http://www.ics.muni.cz/~makub/
Botanicka 68a, 60200 Brno, CZ     mobil: +420-603-533775
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-Djavax.xml.parsers.SAXParserFactory=org.apache.crimson.jaxp.SAXParserFactoryImpl \ -Djavax.xml.transform.TransformerFactory=com.icl.saxon.TransformerFactoryImpl \

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