Threading Issues and Web applications

[faisal khan]

kindly shares views regarding handling threading issues during Web application devlopment.

Following are the areas that developer should think?

1)Session Object handling.
2)Database handling.
3)Using non synchronized Java data structures like ArrayList VS Vector

[William Brogden]

1)Session Object handling.
** Remember that although a given session is tied to a browser by the unique ID, the browser may make multiple requests "at the same time" so you can NOT rely on thread-safe handling of session objects.
2)Database handling.
** Use a DB connection pool, don't keep DB connections as session objects or instance objects.
3)Using non synchronized Java data structures like ArrayList VS Vector
** Depends entirely on the program architecture, no generalization possible.
Bill

[faisal khan]

ok fine now tell me if i use DAO classes for database,
and they are locally created in servlet doGet or doPost, are they thread safe or not.

another i dont understand session handling is also not thread safe?

regards
Faisal

[Bear Bibeault]

Once you realize that multiple instances of the same servlet can be executed simultanously in separate threads, all of your question becomes no different that dealing with threading issues elsewhere.

So, automatic variables that you create inside your servlet methods are safe as they are created on the thread's stack.

Read/write session access is not safe as multiple threads can be accessing the same structures simultaneously.