Exposingcn163

IKVM.
NETBuildingaJavaVMonthe.
NETFrameworkJeroenFrijtersWhoamIJeroenFrijters/YeroonFrighters/Co-founderofasmallISVinTheNetherlandsLeaddeveloperofIKVM.
NETanOpenSourceJVMfor.
NETWhatisIKVM.
NETJavaVMontopof.
NET&Mono–JITcompilertotranslateJavabytecodeintoMSIL–Reflection–Etc.
StaticcompilerthattranslatesJavaclasses/jarsinto.
NETassemblies–BasicallyaheadoftimecompilerforabovementionedJIT.
NETportofOpenJDKclasslibrary–Somegaps,butmostAPIspartof"Java"areavailableWhyisIKVM.
NETStartedinthespringof2002asanexperimentMyblogonJune19th,2002:"IhavealargeJavaapplicationthatIwouldliketoslowlymigrateto.
NET,inordertobeabletodothat,IneedawaytointeroperatewithJavacode,theexistingsolutionsIhavelookedatareinadequate.
Besides,It'slotsoffuntobuildsomethinglikethis:-)"CompatibilityJava7–BasedOpenJDKclasslibrarywithoutthenativecode.
–Swing/AWT/Fonts/Graphics/Printingnotsupported.
TherearesomeminorVMlevelincompatibilities,butsofarthesearejusttheoretical.
Practicalsourcesofincompatibilities:–sun.
*packages–"Theclassloaderproblem"[System|IKVM].
ReflectionThankstoAppDomain.
TypeResolveeventitispossibletobuildamanaged"JIT".
But,System.
Reflectionhassomeseriouslimitationsforcompilers.
IKVM.
Reflectionisnowusedbyikvmc,MonoC#compiler,Scala.
NETandothers.
TypeSystemcli.
System.
Objectextendsjava.
lang.
Objectjava.
lang.
Object:System.
Objectjava.
lang.
Stringisonlyacontainerforstaticmethods.
InstancesarealwaysSystem.
String.
cli.
System.
Exceptionsextendsjava.
lang.
Throwablejava.
lang.
Throwable:System.
Exception(checkedexceptions)TypeSystemcont.
java.
lang.
Comparable:System.
IComparablejava.
lang.
Cloneable,java.
io.
Serializable&java.
lang.
CharSequenceneedtobespecialcased(stringsandarrays)Exposing.
NETfeaturestoJavaDelegatesByRefmethodargumentsCustomattributesValueTypesEnumsProperties&EventsDelegatesinJavapublicfinalclassRunnableDelegateextendscli.
System.
MulticastDelegateimplementsRunnable{publicRunnableDelegate(Methodm){}publicnativevoidInvoke();publicinterfaceMethod{voidInvoke();}publicvoidrun(){Invoke();}}DelegatesinJavapackageikvm.
runtime;publicfinalclassDelegates{publicstaticRunnabletoRunnable(RunnableDelegatedelegate){returndelegate;}}java.
lang.
Threadthread=newjava.
lang.
Thread(ikvm.
runtime.
Delegates.
toRunnable(delegate{Console.
WriteLine("HelloWorld");}));thread.
start();ByRefMethodArgumentsSameasinJava,hackitwithanarrayWouldliketousegenerics,buterasuremakesthishard(duetoinabilitytodomethodoverloading)CustomAttributesExposingthemasannotationsworks(mostofthetime)packagesun.
misc;classUnsafe{@SecurityPermissionAttribute.
Annotation(value=SecurityAction.
__Enum.
LinkDemand,UnmanagedCode=true)@cli.
System.
Security.
SecurityCriticalAttribute.
AnnotationpublicvoidfreeMemory(longaddress){Marshal.
FreeHGlobal(IntPtr.
op_Explicit(address));}}ValueTypesWeaksupport:–YoucanonlyusethemfromJava,notdefinethem.
–Willusuallybeboxed.
EnumsWouldliketheabilitytodomethodoverloadingbasedonenumtypeNeedabilityto"bittwiddle"Usableincustomattributeannotationspackagecli.
System;publicfinalclassDayOfWeekextendscli.
System.
Enum{publicstaticfinalintSunday=0;publicstaticfinalintMonday=1;…publicfinalintValue;publicstaticnativeDayOfWeekwrap(inti);}Properties&EventsNospecialsupportDirectlyusetheunderlyingmethodsimportcli.
System.
Windows.
Forms.
*;classDemo{publicstaticvoidmain(String[]args){Formform=newForm();form.
set_Width(400);form.
set_Height(400);form.
add_FormClosing(newFormClosingEventHandler(newFormClosingEventHandler.
Method(){publicvoidInvoke(Objectsender,FormClosingEventArgsargs){System.
out.
println("Closing.
.
.
");}}));Application.
Run(form);}}ExposingJavato.
NETKeepingIntelliSensecleanStaticfieldsininterfacesAnnotationsGenericsWorkaroundsExposingJavato.
NETKeepingIntelliSensecleanStaticfieldsininterfacesAnnotationsGenericsWorkarounds__WorkaroundBaseClass__publicabstractclassBase{protectedabstractvoidM();}publicabstractclassDerived:Base{publicoverridevoidM(){}}classProgram:Derived{}errorCS0534:'Program'doesnotimplementinheritedabstractmember'Base.
M()'publicabstractclassBase{protectedabstractvoidM();}[HideFromJava][EditorBrowsable(EditorBrowsableState.
Never)]publicabstract__WorkaroundBaseClass__Derived:Base{protectedoverridevoidM(){thrownewAbstractMethodError();}}publicabstractclassDerived:__WorkaroundBaseClass__Derived{publicoverridevoidM(){}}__WorkaroundBaseClass__classProgram:Derived{}Interop"Magic"Limitedsupportforautomagic.
NETserializationsupportforJavaserializableclasses.
NETexceptionsareserializedascom.
sun.
xml.
internal.
ws.
developer.
ServerSideExceptionjava.
io.
Closeable=>System.
IDisposablejava.
lang.
Iterable=>System.
IEnumerablejava.
lang.
AutoCloseableSystem.
IDisposable"JarHell"HardtodeterminejardependenciesCirculardepenciesoccurmoreoftenthanyou'dthinkikvmc{foo.
jar-out:Foo.
dll}{bar.
jar-out:Bar.
dll}PerformanceTypicallyprettygood.
NEToftenwinsonstringprocessingExceptionheavycodesuffersDon't"benchmark"underthedebugger!
UsersSeveralcommercialandopensourceapplicationsuseIKVM.
NET"AtmycompanywearestillamazedtoseelargepartofourJavasystemsuccessfullyrunningon.
NETplatformthankstoIKVM.
"AndyMalakov,DeltixLab,Inc.
"WeareveryhappywithIKVM.
ItenablesustodevelopourcorelibrariesinJavaandcompileforusein.
NET.
TheIKVMteamisveryresponsiveandknowledgeableabouttheissueswewerefacing.
"ShamusNeville,eTradingandAnalyticsGroupatHSBC"HavingusedIKVMforoverayear,wehavefoundIKVMtoworkreliablyandofferproductionqualityoperation.
Theonetimewherewedidrunintosomespecificproblem,theopensourcenatureofIKVMallowedustoquicklytrackdownthebugandverifythecauseoftheproblem.
Wehadafixfortheproblemtheverysameday.
"OttoPerdeck,ChordiantSoftwareMoreathttp://www.
ikvm.
net/stories.
htmlQuestionsMoreInformationProjectWebsite:http://www.
ikvm.
net/jeroen@frijters.
nethttp://weblog.
ikvm.
net/@JeroenFrijters