ThreadLocal usage in enterprise application

Question

If my web application and ejb application are on the same machine (on same JVM) and all the ejb calls are local calls , will the use of ThreadLocal create any issue while passing information from web to ejb?

Any workaround if the ejb calls are remote? Will ThreadLocal information be available from web application to ejb application? Is use of ThreadLocal advisable in such scenario?

Answer 1

For the first question, there is no problem as long as you remove the ThreadLocal variables at the end of every call. This is important because containers (servlet or ejb) typically use threadpools and therefore reuse threads, this has two effects: one "call" may see threadlocal info coming from a previous call, and if you remove an app from the container without stopping the JVM some classes may not be garbage collected because they are still referenced by a container thread. So put data in a threadlocal in a try / finally block and remove in the finally part.

Here is a post showing one way to handle the problem: ThreadLocal in web applications

For the second question as data is threadlocal it will not come with a remote call, you have to add a parameter to your interfaces, extract threadlocal data on one side and recreate it on the other side...