在Java EE环境中测试乐观锁定

Question

As I understand if a row in a database table is updated simultaneously by multiple threads the database would flag an error.

In our production environment we have 2 Tomcat servers in a cluster. It might happen that the two users are directed to each one of the Tomcat servers at the same time and they update the same record in the database table. As a result, an exception would be thrown.

How do I simulate this situation on my local machine? Or how would I do it some environment which is same as production?

Technology that I am working on: Java 6, Spring 3, Hibernate, MS SQL Server 2008 and Tomcat 7.

Answer 1

As I understand if a row in a database table is updated simultaneously by multiple threads the database would flag an error.

Not necessarily. If you run two statements like these below,

UPDATE foo SET bar=baz WHERE bah=doh;

database could simply schedule to run these queries one after another. But there are plenty of possibilities for a deadlock and, generally speaking, result depends on your queries and their timing, data set, etc.

Answer 2

You wan't to simulate the scenario. I read it as you want to test the code which handles optimistic lock exception. I would simply simulate the class which throws exception and explicitly throw OptimisticLockException. Use the simulated class inside exception handler in test environment and write a test fr exception handler.

I believe you are not worried about testing whether optimistic lock is working or not. As it is the job of Hibernate developers.

Answer 3

You can simulate it by using two transactions. Start the first tx. Start the second tx. Make some changes in the first TX and commit it. Make some changes in the second TX and commit it. Hibernate should give you the OptimisticLockException.