How to do it...

This recipe will take you through three scenarios. Let's get started:

1. 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++;
    }

}

2. In the second scenario, LockType is defined at the method level:

@Singleton
@ConcurrencyManagement(ConcurrencyManagementType.CONTAINER)
@AccessTimeout(value = 10000)
public class UserMethodLevelBean {

    private int userCount;
    
    @Lock(LockType.READ)
    public int getUserCount(){
        return userCount;
    }
    
    @Lock(LockType.WRITE)
    public void addUser(){
        userCount++;
    }
}

3. The third scenario is a self-managed bean:

@Singleton
@ConcurrencyManagement(ConcurrencyManagementType.BEAN)
public class UserSelfManagedBean {

    private int userCount;

    public int getUserCount() {
        return userCount;
    }
    
    public synchronized void addUser(){
        userCount++;
    }
}

Now, let's see how this recipe works.