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catch unsupported class version error

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  catch unsupported class version error Philipp Kraus <philipp.kraus@flashpixx.de> - 2015-02-01 23:49 +0100
    Re: catch unsupported class version error Arne Vajhøj <arne@vajhoej.dk> - 2015-02-01 18:00 -0500
      Re: catch unsupported class version error v_borchert@despammed.com (Volker Borchert) - 2015-02-02 00:29 +0000
        Re: catch unsupported class version error Arne Vajhøj <arne@vajhoej.dk> - 2015-02-01 21:26 -0500
    Re: catch unsupported class version error Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2015-02-02 06:53 +0000

#30992 — catch unsupported class version error

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Hello,

I use a Maven build to create a Jar file from my program. I'm using the 
Maven options

<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>

because within the source I use some 1.8 features e.g. thread-stealing pool.
If I run the Jar on a version < 1.8 I get the error "unsupported 
major.minor version" with a stacktrace.
IMHO I cannot catch the error, because it is thrown by a native method 
of the VM, I have found a solution,
that I can compile a class with e.h. 1.7 option and check the running 
version of the VM and create an error
message on a wrong version. 

I would like to create error like "You are need Java 1.8" and the user, 
which run's the Jar does not see the stacktrace.
How can I do check the VM version and create a nice error message?

Thanks

phil

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#30993

On 2/1/2015 5:49 PM, Philipp Kraus wrote:
> because within the source I use some 1.8 features e.g. thread-stealing pool.
>
> If I run the Jar on a version < 1.8 I get the error "unsupported
> major.minor version" with a stacktrace.
>
> IMHO I cannot catch the error, because it is thrown by a native method
> of the VM, I have found a solution,
>
> that I can compile a class with e.h. 1.7 option and check the running
> version of the VM and create an error
>
> message on a wrong version.
>
> I would like to create error like "You are need Java 1.8" and the user,
> which run's the Jar does not see the stacktrace.
>
> How can I do check the VM version and create a nice error message?

Maybe:
    System.getProperty("java.version")

Arne

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#30995

Arne Vajh??j wrote:
> On 2/1/2015 5:49 PM, Philipp Kraus wrote:
> > because within the source I use some 1.8 features e.g. thread-stealing pool.
> >
> > If I run the Jar on a version < 1.8 I get the error "unsupported
> > major.minor version" with a stacktrace.
> >
> > IMHO I cannot catch the error, because it is thrown by a native method
> > of the VM, I have found a solution,
> >
> > that I can compile a class with e.h. 1.7 option and check the running
> > version of the VM and create an error
> >
> > message on a wrong version.
> >
> > I would like to create error like "You are need Java 1.8" and the user,
> > which run's the Jar does not see the stacktrace.
> >
> > How can I do check the VM version and create a nice error message?
> 
> Maybe:
>     System.getProperty("java.version")

What about 

	try {
	  Class.forName("some.class.compiled.with.1_8")
	} catch (UnsupportedClassVersionError e) {
	  ...
	} catch (ReflectiveOperationException e) {
	  ...
	}

-- 

"I'm a doctor, not a mechanic." Dr Leonard McCoy <mccoy@ncc1701.starfleet.fed>
"I'm a mechanic, not a doctor." Volker Borchert  <v_borchert@despammed.com>

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#30998

On 2/1/2015 7:29 PM, Volker Borchert wrote:
> Arne Vajh??j wrote:
>> On 2/1/2015 5:49 PM, Philipp Kraus wrote:
>>> because within the source I use some 1.8 features e.g. thread-stealing pool.
>>>
>>> If I run the Jar on a version < 1.8 I get the error "unsupported
>>> major.minor version" with a stacktrace.
>>>
>>> IMHO I cannot catch the error, because it is thrown by a native method
>>> of the VM, I have found a solution,
>>>
>>> that I can compile a class with e.h. 1.7 option and check the running
>>> version of the VM and create an error
>>>
>>> message on a wrong version.
>>>
>>> I would like to create error like "You are need Java 1.8" and the user,
>>> which run's the Jar does not see the stacktrace.
>>>
>>> How can I do check the VM version and create a nice error message?
>>
>> Maybe:
>>      System.getProperty("java.version")
>
> What about
>
> 	try {
> 	  Class.forName("some.class.compiled.with.1_8")
> 	} catch (UnsupportedClassVersionError e) {
> 	  ...
> 	} catch (ReflectiveOperationException e) {
> 	  ...
> 	}

That should also work.

But I would prefer an if statement over try catch to check
the version.

Arne

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#30999

Philipp Kraus <philipp.kraus@flashpixx.de> wrote:
> I use a Maven build to create a Jar file from my program. I'm using the 
> Maven options
><maven.compiler.source>1.8</maven.compiler.source>
><maven.compiler.target>1.8</maven.compiler.target>
> because within the source I use some 1.8 features e.g. thread-stealing pool.

I got curious about "thread-steling pool" and googled it.
First hit was class ForkJoinPool, and the link pointed to the
javadoc of 7.  You might use other 1.8-features, but the example
you gave seems not to be one of them.

> I would like to create error like "You are need Java 1.8"

I'm not a grammer-nazi about postings, but if the context
is some wording to be used elsewhere then I am ;-)
That said, leave the "are" out of the message: "You need ..."

For the actual question there were already answers, but to add to
them: at least the starting class (the one with the static main
method) *needs* to be compiled with source&target 1.7 or even lower.
If the running JVM cannot load your main class, then any version
checking within it is obviously moot.

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