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can multiple processes access another class exclusively

Posted on 2004-03-28
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Last Modified: 2010-08-05
hi,
  i have three listener programs running in 3 consoles which listen to different queues.now i have a conection program which i call from my 3 listeners.the problem is that only 1 connection must be made at one time.i tried implementing the connection class as a singleton,but it doesnt work as the 3 listeners operate as 3 diff processes(my understanding).however if i implement all 3 listeners in 1 single program and start 1 program in console then the singleton works fine. so my question is is there a way i can synchronize the connection class from 3 listener programs running seperately in different consoles???  
maybe my understanding is wrong.excuse me if it is.

any help will be highly appreciated... !!!!
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Question by:illusionz70
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Expert Comment

by:Mayank S
ID: 10701909
What is it that you want the listener classes to do? And what is the connection program doing? Please explain their functionalities.
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LVL 30

Expert Comment

by:GrandSchtroumpf
ID: 10702063
your 3 programs are running in their own environment.
it's like having them running on 3 different computers.
if you want them to communicate, you'll need some kind of client/server architecture.
you could use RMI to acheive that.
but if it's only to obtain a lock on some process, you could simply use a "file lock".
before your program makes a connection, it can check if the file exists.
if the file does not exist, create a file make your connection and delete the file when you are done.
if the files exists, then wait for it to be deleted by the program that has the lock.
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Accepted Solution

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Webstorm earned 175 total points
ID: 10703575
>> but if it's only to obtain a lock on some process, you could simply use a "file lock".
Some synchronization problem will happen :
  P1: file doesn't exist (true)
                     P2:  file doesn't exist (true)
  P1: create the file, use the connection
                     P2: create the file, use the connection

The solution is to use RMI, and use synchronized methods to access the connection.



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Author Comment

by:illusionz70
ID: 10712242
but the connection program is a .java file as well and i need an object or instance of the connection.java ad only 1 listener.java must be able to get access to that instance at a time.is this possible with file locks?????

thanks..for all replies and sorri for my late reply .
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Author Comment

by:illusionz70
ID: 10747323
File locks work on 1.4 ...i am aloowed to use only 1.3.1 . do i have any alternate options or is it possible to import the filelock library in 1.3.1.

i think a filelock server should go well as different processes can get the lock on file by calling this dedicated server...!!!
ne thoughts...???
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