Same JVM multiple processes?

Question

Summary: Does any one know how to get a JVM to be shared across different Windows processes, as follows:
Context: I have created a Java ActiveX component. This is instantiated and used as an object embedded in HTML. The HTML will always be executed in Internet Explorer. When I have multiple windows open in the same Internet Explorer process with the same HTML code the static variables are shared by all the Java ActiveX components. If I have multiple process of Internet Explorer open each with the same HTML code the static variables are not shared because different instances of the JVM are running in each Internet Explorer process.
Question: Is it possible to do any of the following:
- Get multiple instances of the JVM to run as multiple Threads i.e. not as separate processed with separate memory segments?
- Get multiple instances of the JVM to share variables?
- Prevent multiple instances of the JVM being created so that all Java objects run in the same JVM regardless of the process that instantiated them.
This is possible in C++ ActiveX components using shared segments across different Internet Explorer processes, as follows:
// in DLL .cpp file
#pragma data_seg (�.mydata�)
int sharedVariable = 1;
#pragma data_seg ( )
#pragma comment(linker, �/SECTION:.mydata, RWS�)Therefore I would expect that if I could achieve a similar approach with Java this would not be prevented by the OS (i.e. Windows) due to memory faults, etc. I know that Java has different (less) memory handling capabilites so this may not be possible but any suggestions would be very much appreciated.
Thanks,
J

Answer 1

Summary: Does any one know how to get a JVM to
be shared across different Windows processes, as
follows:
Context: I have created a Java ActiveX
component. This is instantiated and used as an
object embedded in HTML. The HTML will always be
executed in Internet Explorer. When I have multiple
windows open in the same Internet Explorer process
with the same HTML code the static variables are
shared by all the Java ActiveX components. If I have
multiple process of Internet Explorer open each with
the same HTML code the static variables are not
shared because different instances of the JVM are
running in each Internet Explorer process.
Question: Is it possible to do any of the
following:
- Get multiple instances of the JVM to run as
s multiple Threads i.e. not as separate processed
with separate memory segments? No, each instance of the VM is a seperate process. The closest you can come without hacking the VM and/or IE, is running multiple Java programs in the same VM, each in its own thread.
- Get multiple instances of the JVM to share
e variables?
- Prevent multiple instances of the JVM being
g created so that all Java objects run in the same
JVM regardless of the process that instantiated them.
RMI provides some means of inter-VM communication, but this is probably not suitable for your application. The combination of JNI + NIO also provide some capability for the VM to share memory with native processes, but its not immediately obvious to me how to extend this capability to multiple VM's.
>
This is possible in C++ ActiveX components using
shared segments across different Internet Explorer
processes, as follows:
// in DLL .cpp file
#pragma data_seg (�.mydata�)
int sharedVariable = 1;
#pragma data_seg ( )
#pragma comment(linker, �/SECTION:.mydata,
RWS�)Therefore I would expect that if I could achieve a
similar approach with Java this would not be
prevented by the OS (i.e. Windows) due to memory
faults, etc. I know that Java has different (less)
memory handling capabilites so this may not be
possible but any suggestions would be very much
appreciated.
Thanks,
JAlso, you may want to keep in mind that VM's that run in a browser have a SecurityManager installed that restricts them from performing certain restricted operations. For this reason it may be difficult to do anything really ambitious with an applet or, presumably, a Java ActiveX control, though I have no idea what that is.
Good luck.