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JVM and java application

 
 
Jack
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      01-25-2010
If there are several java applications/programs running on the same
machine, are these java applications/programs using their own JVMs or
are they share the same JVM?

Thanks.
 
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Knute Johnson
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      01-25-2010
On 1/24/2010 7:56 PM, Jack wrote:
> If there are several java applications/programs running on the same
> machine, are these java applications/programs using their own JVMs or
> are they share the same JVM?
>
> Thanks.


Each time you start a Java app, you create a new JVM. That's not to say
that you can't have a Java program that loads other Java programs if you
want them run on the same JVM. I don't know what the state of things is
in browsers for sure but I would suspect that every applet that is
loaded gets its own JVM.

--

Knute Johnson
email s/nospam/knute2010/

 
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Mike Schilling
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      01-25-2010
Knute Johnson wrote:
> On 1/24/2010 7:56 PM, Jack wrote:
>> If there are several java applications/programs running on the same
>> machine, are these java applications/programs using their own JVMs
>> or
>> are they share the same JVM?
>>
>> Thanks.

>
> Each time you start a Java app, you create a new JVM. That's not to
> say that you can't have a Java program that loads other Java
> programs
> if you want them run on the same JVM. I don't know what the state
> of
> things is in browsers for sure but I would suspect that every applet
> that is loaded gets its own JVM.


Web servers and application servers, in general, run all of their
applications in a single JVM (or perhaps a replicated set of JVMs,
each of which can run any of their applications.)


 
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Arne Vajhj
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      01-26-2010
On 25-01-2010 01:17, Mike Schilling wrote:
> Knute Johnson wrote:
>> On 1/24/2010 7:56 PM, Jack wrote:
>>> If there are several java applications/programs running on the same
>>> machine, are these java applications/programs using their own JVMs
>>> or
>>> are they share the same JVM?

>>
>> Each time you start a Java app, you create a new JVM. That's not to
>> say that you can't have a Java program that loads other Java
>> programs
>> if you want them run on the same JVM. I don't know what the state
>> of
>> things is in browsers for sure but I would suspect that every applet
>> that is loaded gets its own JVM.

>
> Web servers and application servers, in general, run all of their
> applications in a single JVM (or perhaps a replicated set of JVMs,
> each of which can run any of their applications.)


Java EE has a different application concept than Java SE.

Seen from Java SE perspective the app server is the app
and the ear's are plugins.

Seen from Java EE perspective the ear's are multiple apps.

Arne

 
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Roedy Green
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      01-26-2010
On Sun, 24 Jan 2010 19:56:59 -0800 (PST), Jack <(E-Mail Removed)>
wrote, quoted or indirectly quoted someone who said :

>If there are several java applications/programs running on the same
>machine, are these java applications/programs using their own JVMs or
>are they share the same JVM?


logically they each have their own JVM, unless you use Echidna.
See http://mindprod.com/jgloss/echidna.html

However most of the JVM on windows is implemented with DLLs which is
shared code. So you have shared code and separate heaps for data.
--
Roedy Green Canadian Mind Products
http://mindprod.com
Dont be discouraged by a failure. It can be a positive experience. Failure is, in a sense, the highway to success, inasmuch as every discovery of what is false leads us to seek earnestly after what is true, and every fresh experience points out some form of error which we shall afterwards carefully avoid.
~ John Keats (born: 1795-10-31 died: 1821-02-23 at age: 25)
 
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Roedy Green
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      01-26-2010
On Mon, 25 Jan 2010 22:42:38 -0800, Roedy Green
<(E-Mail Removed)> wrote, quoted or indirectly quoted
someone who said :

>
>logically they each have their own JVM, unless you use Echidna.
>See http://mindprod.com/jgloss/echidna.html
>
>However most of the JVM on windows is implemented with DLLs which is
>shared code. So you have shared code and separate heaps for data.


Even though they share code, the who JVMs are not aware of the
existence of the other.

OS puts code in read-only, thus shareable memory. It puts data is
separate read-write memory.

The RAM hardware is identical. It is just the memory addressing
hardware is told to block writes to parts of RAM containing code.
--
Roedy Green Canadian Mind Products
http://mindprod.com
Dont be discouraged by a failure. It can be a positive experience. Failure is, in a sense, the highway to success, inasmuch as every discovery of what is false leads us to seek earnestly after what is true, and every fresh experience points out some form of error which we shall afterwards carefully avoid.
~ John Keats (born: 1795-10-31 died: 1821-02-23 at age: 25)
 
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