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From "Jack Cai" <greensi...@gmail.com>
Subject Re: Re: [general] features
Date Wed, 07 Jan 2009 09:29:04 GMT
So to quickly answer your questions -

#2: No, neither SUN JVM nor Harmony JVM support such "hibernate" operation.
JVM does not have an abstract Hardware level, even though it does manage the
memory and threads for a running process. So it is not a "real" operating
system. It accesses resources by calling the hosting OS's native APIs
directly. As a result, it's not as easy to hibernate a JVM as we do with
Windows, VMWare, etc.

#3: Yes, sandbox is the built-in Java security model. You can achieve what
you described through a customized SecurityManager. You can search google to
find enough to read.

- Jack

2009/1/7 Rui Chu <rchu@nudt.edu.cn>

> Thank you, Xiaofeng.
> About Java Isolation, I am not sure whether SUN JVM implements it. If not,
> maybe the benefit of Isolation is still trivial to motivate the guys in SUN,
> although it looks nice in the proposal.
> About the second question, as you know, VMWare, as well as other
> system-level virtual machines, can suspend the guest operating system when
> you press the 'suspend' button. You can also resume it later, or even resume
> it in another host system. This feature really looks charming in my mind.  I
> think JVM can also support it more easily because JVM has a relative simpler
> architecture then the system-level VMs (although it is still complex). I
> wonder if current Harmony or SUN JVM could do that.
> The sandbox in my third question does not only mean Applet. In my vision,
> it should support general java applications. The execution of the
> application is monitored and restricted, especially the operations through
> JNI. For example, the java application cannot  access the native file system
> with the same privilege of JVM, and it can only accesses a virtualized file
> system instead. Is there any project or plan in Harnony or SUN JVM to do
> that?
> Thanks again, Xiaofeng. I have read some documents and source codes. But
> the souce codes can only prove what has been done in Harmony, while cannot
> tell me what is still not implemented. :)  If possible, I want to continue
> to discuss this topic with you. Waiting for you kind response. Anybody else
> want to join the topic are also appreciated.
> ------------------
> Rui Chu
> 2009-01-07
> -------------------------------------------------------------
> 发件人:Xiao-Feng Li
> 发送日期:2009-01-07 08:35:56
> 收件人:dev
> 抄送:
> 主题:Re: [general] features
> Rui, thanks for your interests in Harmony. My personal opinions are
> inlined below.
> On Wed, Jan 7, 2009 at 12:39 AM, Rui Chu <rchu@nudt.edu.cn> wrote:
> > Hi,
> > I am a new comer of JVM and Harmony. Since I have just learnt Harmony for
> a few time, I wonder whether Harmony(especially the VM) has implemented or
> has been interested in the features as follows.
> > 1. SUN has proposed Java Isolation for a long while, and related
> specifications have also been released. Unfortunately I cannot find any
> support for it in SUN JVM till now. Has Harmony implemented or planned to do
> that? Or maybe SUN has implemented but I do not know it yet.
> [XF] I personally don't really see the needs to implement Isolation in
> Harmony. But it is welcomed if anybody wants to have a try and I'd
> like to help. I had some experience in it.
> > 2. Does SUN JVM or Harmony support to suspend, serialize and resume the
> JVM? In other words, a JVM can suspend the execution of itself and
> bytecodes, transfer the execution status into an image file and resume it
> later. Assuming the external environments such as file system or network
> connection still keeps.
> [XF] If I understand you correctly, the feature you described is the
> fundamental feature of a JVM for garbage collection and exception
> throwing. So all serious JVMs have it.
> > 3. Does the sandbox support appear as an independent project, or has been
> integrated in Harmony? Where can I find more documents about the sandbox in
> Harmony?
> [XF] I am not sure what you mean with sandbox. If you mean Applet
> support, yes, Harmony has it (almost done).
> > In general, I want to know whether Harmony planned to be another (open
> source) implementation of SUN JVM, or has its special features beyond the
> latter? I am not familiar with both SUN JVM and Harmony, so my question may
> be naive :)  Your kind and patient answers are appreciated.
> [XF] Please read some documents on Apache Harmony in its website. That
> will help you to have a basic understanding. Harmony is an open source
> Java SE implementation under Apache license. I personally think
> Harmony wants to be compatible at first, and might have some special
> features.
> Thanks,
> xiaofeng
> > Thanks a lot!
> >
> >
> >
> >
> > Rui Chu
> >
> >
> >
> --
> Managed Runtime Technology Center, Intel
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