ThreadLocal - Usage and Explanation

Refer to a developer article : http://java.dzone.com/articles/java-thread-local-%E2%80%93-how-use

Read documentation on usage first in the above link. Then refer to the following sample code from the developer:

01.package com.veerasundar;

02. 

03.public class Context {

04. 

05.  private String transactionId = null;

06. 

07.        /* getters and setters here */

08. 

09.}

 

01.package com.veerasundar;

02. 

03./**

04. * this class acts as a container to our thread local variables.

05. * @author vsundar

06. *

07. */

08.public class MyThreadLocal {

09. 

10.  public static final ThreadLocal userThreadLocal = new ThreadLocal();

11. 

12.    public static void set(Context user) {

13.      userThreadLocal.set(user);

14.  }

15. 

16.   public static void unset() {

17.        userThreadLocal.remove();

18.   }

19. 

20.   public static Context get() {

21.       return userThreadLocal.get();

22.   }

23.}

 

01.package com.veerasundar;

02. 

03.public class ThreadLocalDemo extends Thread {

04. 

05.   public static void main(String args[]) {

06. 

07.        Thread threadOne = new ThreadLocalDemo();

08.       threadOne.start();

09. 

10.      Thread threadTwo = new ThreadLocalDemo();

11.       threadTwo.start();

12.  }

13. 

14.   @Override

15.   public void run() {

16.     // sample code to simulate transaction id

17.       Context context = new Context();

18.        context.setTransactionId(getName());

19. 

20.        // set the context object in thread local to access it somewhere else

21.       MyThreadLocal.set(context);

22. 

23.     /* note that we are not explicitly passing the transaction id */

24.        new BusinessService().businessMethod();

25.     MyThreadLocal.unset();

26. 

27.  }

28.}

 

01.package com.veerasundar;

02. 

03.public class BusinessService {

04. 

05.  public void businessMethod() {

06.      // get the context from thread local

07.        Context context = MyThreadLocal.get();

08.      System.out.println(context.getTransactionId());

09. }

10.}