can anybody provide me a simple example of concurrency control in servlet

[bighead4694]

Hi,

I am using jsp/servlet to create a web application. In this
application, i need to insert new users into db. but before insertion,
i have to check whether the user has already been in the db. I think
concurrency control should be used, but I have no idea how to achieve
concurrency control or transaction management in servlet. Can anybody
give me a simple example? Thanks!

bighead4694

 

[nuklea]

forget about concurrency stuff, create your table schema correctly and
let the db engine handle duplicate record. in your code just check the
return code after the insertion attempt.

 

[Wendy S]

I am using jsp/servlet to create a web application. In this
application, i need to insert new users into db. but before insertion,
i have to check whether the user has already been in the db. I think
concurrency control should be used, but I have no idea how to achieve
concurrency control or transaction management in servlet. Can anybody
give me a simple example? Thanks!

This doesn't have anything to do with JSP or Servlets. If you can't do it
with "regular" Java code, learn how to do that first, and build a set of
classes that interacts with the database. Then call those from your
Servlet.

 

[anonymous]

Hi,

I am using jsp/servlet to create a web application. In this
application, i need to insert new users into db. but before insertion,
i have to check whether the user has already been in the db. I think
concurrency control should be used, but I have no idea how to achieve
concurrency control or transaction management in servlet. Can anybody
give me a simple example? Thanks!

bighead4694

Is this a school project? Normally, you'd use constraints aka
referential integrety. This would prevent duplicates.

 

[bighead4694]

Hi,
I am able to code the java classes to interact with the database. but i
am not able to code the java classes to achieve the concurrency control
or transmission management. This web application is part of my thesis
project. My supervisor checked my codes and suggested me imporve the
concurrency control stuff. To be honest I have no idea about it. Do you
have any simple examples that can help me through?

 

[Ann]

Hi,
I am able to code the java classes to interact with the database. but i
am not able to code the java classes to achieve the concurrency control
or transmission management. This web application is part of my thesis

What grade are you in?

 

[John C. Bollinger]

I am able to code the java classes to interact with the database. but i
am not able to code the java classes to achieve the concurrency control
or transmission management. This web application is part of my thesis
project. My supervisor checked my codes and suggested me imporve the
concurrency control stuff. To be honest I have no idea about it. Do you
have any simple examples that can help me through?

So your DB access object requires a method insertNewUser(...) that
performs the check and insert. If this is the only way that users will
be added, if they will never be removed, and if only one instance of the
DB access class can ever be in use at a time, then it is sufficient to
just synchronize that method. In any other case you need a shared
synchronization object on which to synchronize the bodies of methods
that add, remove, or query the presence users in the DB.

You can exert control over DB transactions (if the DB itself and its
driver support it) by invoking Connection.setAutocommit(false), and then
using Connection.commit() and Connection.rollback() to commit or roll
back transactions where appropriate.


John Bollinger
(e-mail address removed)