Using EJB to deal with concurrency

Concurrency management is one of the biggest advantages supplied by a Java EE server. You can rely on a ready environment to deal with this tricky topic.

This recipe will show you how you can set up your beans to use it!

Getting ready

Just add a Java EE dependency to your project:

        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>

How to do it...

The recipe will show you three scenarios.

In the first scenario, LockType is defined at the class level:

@Singleton
@ConcurrencyManagement(ConcurrencyManagementType.CONTAINER)
@Lock(LockType.READ)
@AccessTimeout(value = 10000)
public class UserClassLevelBean {

    private int userCount;

    public int getUserCount() {
        return userCount;
    }

    public void addUser(){
        userCount++;
    }

}

In...