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The objective of this session is to introduce the subject of software engineering. When you have read this session you will understand what software engineering is and why it is important, know the answers to key questions which provide an introduction to software engineering, understand ethical and professional issues which are important for software engineers.


Virtually all countries now depend on complex computer-based systems. More and more products incorporate computers and controlling software in some form. The software in these systems represents a large and increasing proportion of the total system costs. Therefore, producing software in a cost-effective way is essential for the functioning of national and international economies.

Software engineering is an engineering discipline whose goal is the cost-effective development of software systems. Software is abstract and intangible. It is not constrained by materials, governed by physical laws or by manufacturing processes. In some ways, this simplifies software engineering as there are no physical limitations on the potential of software. In other ways, however, this lack of natural constraints means that software can easily become extremely complex and hence very difficult to understand.

Software engineering is still a relatively young discipline. The notion of ‘software engineering’ was first proposed in 1968 at a conference held to discuss what was then called the ‘software crisis’. This software crisis resulted directly from the introduction of powerful, third generation computer hardware. Their power made hitherto unrealisable computer applications a feasible proposition. The resulting software was orders of magnitude larger and more complex than previous software systems.

Early experience in building these systems showed that an informal approach to software development was not good enough. Major projects were sometimes years late. They cost much more than originally predicted, were unreliable, difficult to maintain and performed poorly. Software development was in crisis. Hardware costs were tumbling whilst software costs were rising rapidly. New techniques and methods were needed to control the complexity inherent in large software systems.

These techniques have become part of software engineering and are now widely although not universally used. However, there are still problems in producing complex software which meets user expectations, is delivered on time and to budget. Many software projects still have problems and this has led to some commentators (Pressman, 1997) suggesting that software engineering is in a state of chronic affliction.

As our ability to produce software has increased so too has the complexity of the software systems required. New technologies resulting from the convergence of computers and communication systems place new demands on software engineers. For this reason and because many companies do not apply software engineering techniques effectively, we still have problems. Things are not as bad as the doomsayers suggest but there is clearly room for improvement.

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Sample Questions from the Enterprise JavaBeans Quiz

Question: What is true about EJB ?


In a deployed application, both session and entity beans are managed by what is called a session container

In a deployed application, both session and entity beans are managed by what is called EJB container

In a deployed application, session beans are managed by what is called SessionContext

In a deployed application, entity beans are managed by what is called EntityContext

Question: What is an Entity Bean?


It is an object representing data which is fetched from and can be stored to a persistent data store

It holds the state of the associated stateful session bean

It is the facade to access the system data store

Question: What is the difference between stateful session beans and stateless session beans?


Stateless session beans are lighter in weight and easier to manage than their stateful counterparts

Stateful session beans are pooled to increase performance due to their heavy content, whereas stateless beans are not pooled for the opposite reason

Both stateful session beans and stateless session beans can survive a server crash.

As the name implies, a Stateful session bean can remember its state with a client, in contrast to a Stateless session bean, which cannot

Question: A Stateful session bean can remember its state and the conversation with the client, but sometimes due to performance issues, the container needs to remove the Stateful session bean from the memory releasing its attached resources, what is true about this process?


The Stateful session bean itself persists itself for later activation

The EJB container is the one responsible for managing and serializing the state of the Stateful Session bean

Just before this process (passivating), the container calls the ejbPassivate() method

Just before this process (passivating), the container calls the ejbRemove() method

Question: Managing permissions to methods (securing invoking methods to specific roles), can be applied by:


using the xml deployment descriptor

using annotations (in EJB 3.x)

using digital signature

programmatically using isCallerInRole() and getCallerPrincipal()

Question: The three types of EJBs are :



Transfer object

Session bean

Message-driven bean

Transaction bean

Entity bean

Question: When to opt BMP (bean-managed persistence) over CMP (container-managed persistence)?


when the application developed will serve a large number of users

when the project budget permits

when you would like to add to your CV a BMP experience

when you data is a mix of relational database and legacy data sources

when CMP does not provided the intended tasks

Question: EJB 3.0 specifications are implemented in :


Java EE 3

Java EE 4

Java EE 5

Question: What is NOT true about Entity beans?


Entity beans can survive a system crash

Entity beans are not pooled

Entity beans cannot be stateless

Entity beans are transactional

Question: When to opt an EJB-centric solution for your yet to be developed system?


when the system is distributed

when the system is transactional

to create a data entry system

when you are developing a content-management system, which serves only static pages

Question: What is not a state in the EJB 3 Entity beans life cycle states?


Does not exist




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