where i need to use the ThreadLocal in Real world?

[ramakrishna rayudu]

Hi..

i have Question that Where we need to use the ThreadLocal In Real world Example..???

Thanks,
Ramakrishna Rayudu.

[Chris Beckey]

The most common usage I know of is to attach security context (user identification, credentials, groups, etc...) to a thread servicing an HTTP request. In that way any of the "downstream" called methods can check the permissions of the original caller.

[Jesper de Jong]

With a ThreadLocal, you can create one copy of some value per thread - so if you have multiple threads that access the value, there will be a separate copy for each thread.

One of the examples that this is sometimes used with is with SimpleDateFormat. Class SimpleDateFormat is not thread-safe; you must not try to use the same SimpleDateFormat object from different threads at the same time, because then you'll get strange results and maybe even exceptions. Look at this:

public class Something {
    // It is not safe to use this from different threads at the same time!
    public static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd");
}

To avoid such problems, you can wrap the SimpleDateFormat in a ThreadLocal, so that there will be a separate instance for each thread:

public class Something {
    public static final ThreadLocal<DateFormat> DATE_FORMAT = new ThreadLocal<DateFormat>() {
        @Override
        public DateFormat initialValue() {
            return new SimpleDateFormat("yyyy-MM-dd");
        }
    };
}

[ramakrishna rayudu]

Thanks for Your Replay..

i didnt get the correct usage.what i got it from your answer is when ever i kept a Object In to the ThreadLocal it will return the
single Instance per Threadn is correct or not..???

Thanks,
Ramakrishna Rayudu