Re: [Jamvm-general] Proof Of Concept : an alternative to OpenJDK

[johann S. <sor...@in...>]

Thanks for the details, 
here are a few more questions :

Is making an implementation of java.lang.* classes an obligation ?

How can I say... I would like to plug in JamVM at a lower level, under the 'java protocol'.
I see there is a specific libjvm.so so it looks like all the java binding occurs in it, so maybe it could be possible to make a different binding ? Is there some kind of jamVM kernel isolated from the java model ?


Johann Sorel



> -----Original Message-----
> From: xe...@za...
> Sent: Wed, 05 Jun 2013 13:00:30 +0200
> To: sor...@in..., jam...@li...
> Subject: Re: [Jamvm-general] Proof Of Concept : an alternative to OpenJDK
> 
> 2013-06-03 23:41, johann Sorel skrev:
>> Hello
> 
> Hi Johann!
> 
>> 
>> I would like some advices from some peoples working on JamVM :
>> 
>> I have been working for several months now on a public domain general
>> purpose library (think of it as a replacement to the ClassPath lib). The
>> projet is going pretty well and is starting to be self sufficient. (for
>> those interested : https://bitbucket.org/Eclesia/un/wiki/Home)
>> 
>> Now I would like to make a Proof Of Concept that my project can live on
>> it's own without the JVM APIs and classes. Basicly I would like to
>> obtain a draft of VM using JamVM as "kernel" and my project as the main
>> library.
> 
> You can use the jamvm libjvm.so standalone in combination with your own
> projects class library
> 
>> 
>> - Can JamVM be used without ClassPath/OpenJDK ?
> yes create your own jvm launcher using the "JNI Invocation Interface"
> I recommend you to take a look at Chapter 7 (page 83) of the "The Java™
> Native Interface Programmer’s Guide and Specification" book
> http://web.archive.org/web/20120905183616/http://java.sun.com/docs/books/jni/download/jni.pdf
> 
>> - Will I need to code some JNI for low level operations ?
>> or are they provided ? (Streams,Sockets,...)
> You need to implement all classes you need like a ClassLoader, String,
> Object and Class class. And you need to use JNI to do low level
> operations.
> 
> 
>> 
>> If you think it is possible : where should I start ?
>> 
>> Thanks
>> 
>> Johann Sorel
> 
> 
> jamvm libjvm finds the JRE classes relative to the libjvm.so thus the
> folder layout is important.
> You may setup a project structure like this:
> 
> jamvmMini$ find .
> .
> ./compile.sh
> ./jre
> ./jre/classes/java/lang/Object.java <-- you will have to provide your own
> implementation of all java/lang classes
> ./jre/classes/java/lang/String.java
> ./jre/classes/java/lang/Class.java
> ./jre/classes/java/lang/ClassLoader.java
> ./jre/classes/java/lang/...
> ./jre/lib/jvm/jamvm/libjvm.so <- jamvm built using instructions from:
> http://draenog.blogspot.se/2011/02/openjdkjamvm-git-repository.html
> ./Prog.java <- the main application to run
> ./myJVM.c <- example code from "Chapter 7 (page 83) of the "The Java™
> Native Interface Programmer’s Guide and Specification" book"
> ./run.sh
> 
> jamvmMini$ cat compile.sh
> #compile launcher
> gcc myJVM.c -ljvm -L./jre/lib/jvm/jamvm/
> #compile java.lang classes
> cd jre/classes
> javac java/lang/*.java
> cd ../../
> #compile application
> javac Prog.java
> #compile jamvm launcher
> gcc myJVM.c -o jamvm-launcher -ljvm -L./jre/lib/jvm/jamvm/
> 
> jamvmMini$ cat run.sh
> #run launcher
> LD_LIBRARY_PATH=./jre/lib/jvm/jamvm/ ./jamvm-launcher
> 
> Cheers
> Xerxes

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