Code once executed at a moment by using threads

Question

Hi
We have a Java program that reads a text-file and then put it into the database (into four different tables). We make use of ADF BC 10g for the interaction with the database.
We make use of threads in a threadpool.
The Java program consists of different methods, for each insert/update into the table there is an own method with an own getTransaction().commit().
There is one method (an update for one table) that can be executed only once at a time, during to locking problems in the database.
When we make use of one thread for this program, things work fine, but when we make use of e.g. 4 threads, then there are 4 instances of the Java-program (for the processing of 4 different text-files), and then we get an error while two 'threads' are updating the same row in the database.
I tried to avoid this by using the keyword 'synchronized', but (in my opinion) this only works when you use the same object in all the threads, so this does not work for me.
Can someone help me to solve this problem?
Regards,
EJ

Answer 1

LvL wrote:
2nd question: do you have an example how to manage this by using DB Transactions.
At this moment I get the error: JBO-26030: Failed to lock the record, another user holds the lock
How can I avoid this?The basic method is to keep the transaction open for as short a time as possible; and the simplest way to do that is to ensure that you are ready to update before you start the transaction. If the information-gathering process is lengthy, do it outside the transaction; then re-read and update, or simply UPDATE, the record in one go (and inside a synchronized method).
If all updates are independent, that's basically it; but if the update involves information that could itself be updated during the gathering process, it may not be so simple. Either way you should try to minimize your transaction to only locking data that can be compromised.
Winston