kapil kulkarni

i have developed aplication using openjms server. and
openjms is very good and easy to use.
but, i am getting one error. i explain with one example.
i have written jms client who is subscriber and
publisher and also queue sender and receiver.
let us say i have instantiated 5 clients a, b, c, d,
e.
if a publishes mesasage to others then erratically,
sometimes happens that b and c fails to receive the
message that is onmessage is not getting called (this
happens sometimes with any of the client randomly and
sometimes it behaves very properly).
the case is though b and c are failing to receive the
messages, then can send or publish the messages to
others.
i have not used durable subscribers. messages are
persistent. and subscribers are listening with message
selectors.
the exception which may be coming in the log of jms
server is ( i am just providing the info which may be
helpful in finding out the root cause of problem):
14:54:18.649 ERROR [Scheduler-Worker-8] -
java.util.ConcurrentModificationException
java.util.ConcurrentModificationException
at
java.util.TreeMap$EntryIterator.nextEntry(TreeMap.java:1022)
at
java.util.TreeMap$KeyIterator.next(TreeMap.java:1047)
at
org.exolab.jms.messagemgr.QueueDestinationCache.getMessage(Unknown
Source)
at
org.exolab.jms.messagemgr.QueueConsumerEndpoint.run(Unknown
Source)
at
org.exolab.core.threadPool.ThreadPoolWorker.runIt(ThreadPoolWorker.java:186)
at
org.exolab.core.threadPool.ThreadPoolWorker.runWork(ThreadPoolWorker.java:173)
at
org.exolab.core.threadPool.ThreadPoolWorker.access$000(ThreadPoolWorker.java:67)
at
org.exolab.core.threadPool.ThreadPoolWorker$1.run(ThreadPoolWorker.java:117)
at java.lang.Thread.run(Thread.java:536)
14:54:38.047 ERROR [Scheduler-Worker-2] -
org.exolab.jms.server.ClientDisconnectionException:
Server returned HTTP response code: 500 for URL:
http://127.0.0.1:8080/openjms/OpenJMSClient
org.exolab.jms.server.ClientDisconnectionException:
Server returned HTTP response code: 500 for URL:
http://127.0.0.1:8080/openjms/OpenJMSClient
at
org.exolab.jms.server.http.HttpJmsSessionSender.onMessage(Unknown
Source)
at
org.exolab.jms.server.JmsServerSession.onMessage(Unknown
Source)
at
org.exolab.jms.messagemgr.QueueConsumerEndpoint.run(Unknown
Source)
at
org.exolab.core.threadPool.ThreadPoolWorker.runIt(ThreadPoolWorker.java:186)
at
org.exolab.core.threadPool.ThreadPoolWorker.runWork(ThreadPoolWorker.java:173)
at
org.exolab.core.threadPool.ThreadPoolWorker.access$000(ThreadPoolWorker.java:67)
at
org.exolab.core.threadPool.ThreadPoolWorker$1.run(ThreadPoolWorker.java:117)
at java.lang.Thread.run(Thread.java:536)
i am confused about this. please guide me in this
regards and thanks in advance for that !!!

I have some doubts regarding setting transaction attributes for
EJB in deployment descriptor.
I explain the situation :
A session beans calls for inserting a new record in a table say X
table.
Method name is insertRow(some params);
This method is having transaction attribute as "requires". Now this method
calls 2 entity beans to insert new records. i.e. first new record is created
with "create" method of X entity bean. It's transaction attribute is
"requires". X table is master table. Now after this some data is
inserted into child table X_CHILD with X_ID as foreign key
(X_ID is primary key in X).
Now "create" method of XChild entity bean is used for this insertion
and its transaction attribute is "requires".
But if this method insertRow(..) of session bean gets executed, we are
getting exception as "parent key not found" while inserting records in
X_CHILD after inserting new record in X.
What should we do in this case ?
If we change transaction attribute of "create" method of X entity bean
to "requires new", we are not getting exception. But if there is some
exception while inserting row in X_CHILD and we get exception then
transaction gets rolled back but as transaction newly started for X entity beans
"create" method is commited it does not get rolled back ?
What should we do in this case ?
Thanks in advance for your help

I have some doubts regarding setting transaction attributes for
EJB in deployment descriptor.
I explain the situation :
A session beans calls for inserting a new record in a table say X
table.
Method name is insertRow(some params);
This method is having transaction attribute as "requires". Now this method
calls 2 entity beans to insert new records. i.e. first new record is created
with "create" method of X entity bean. It's transaction attribute is
"requires". X table is master table. Now after this some data is
inserted into child table X_CHILD with X_ID as foreign key
(X_ID is primary key in X).
Now "create" method of XChild entity bean is used for this insertion
and its transaction attribute is "requires".
But if this method insertRow(..) of session bean gets executed, we are
getting exception as "parent key not found" while inserting records in
X_CHILD after inserting new record in X.
What should we do in this case ?
If we change transaction attribute of "create" method of X entity bean
to "requires new", we are not getting exception. But if there is some
exception while inserting row in X_CHILD and we get exception then
transaction gets rolled back but as transaction newly started for X entity beans
"create" method is commited it does not get rolled back ?
What should we do in this case ?
Thanks in advance for your help

hi friends,
I got thro the SCJP exam today with a score of 83% . I referred this site a lot.especially sincere thanks to maha anna. her discussion(on her site) helped me a lot. i referred mughal which is very good. also i thank to Velmurugan Periaswamy his notes are very concise and excellent, i used them with mughal. and jq+ is fantastic. if you clear all exams in jq+ s/w you can easily clear scjp with good score.
Thanx & regards
kapil
[This message has been edited by kapil kulkarni (edited February 27, 2001).]

If the exception is not handled, the process repeats looking for next enclosing try block up the call hierarchy. If this search reaches the top level of the hierarchy (the point at which the thread was created), then the thread is killed and message stack trace is dumped to System.err.
this statement says that process goes on looking up in the next level thread group(if exists. check uncaughtexception method of threadgroup class, it says this method is called by the Java Virtual Machine when a thread in this thread group stops because of an uncaught exception)/thread and if it does'n find try catch block, uncaught exception message is passed by JVM to System.err which prints it on console and that thread is killed but other threads if any ,are still running, means JVM does not terminate.
Pl correct me if i am wrong.
thanks.

thanks Carol for your prompt reply.
i not getting it perfectly. i am very very weak in this bits/bytes business... not comfortable at all. can you ellaborate more ? what book i can refer for this topic ?
carol, i am not getting this exactly -
When you assign a value to each bit ... the bit to the far right represents 0 or 1. The next bit to the left represents 2 or 0. The next bit represents 0 or 4.
So, each bit to the left is "higher" representing a larger number. That makes the bits to the far right the lower bits or the 8 bits at far right the "lower" byte.

[This message has been edited by kapil kulkarni (edited February 01, 2001).]

the write(..) method in FileOutputStream writes ONLY the LOWER BYTE of the argument.
will anybody clear me what is this LOWER BYTE ?
i am not getting this .....

Originally posted by anurag priya:
hi! if there is anyone preparing for SCJP then please contact me anurag99@excite.com
i am going to appear in the first or second weak of feb!
anurag!

i am from pune. already mailed you a message. contact me. would like to join you....