Why EJB?

Introduction

When people think of Java EE, they think in first hand of EJB, even though the EE specification contains much than EJB. For example Rod Johnson (founder of Spring) pointed out in the Expert One-on-One J2EE Development without EJB that JDBC, JTA and JMS are successful parts of EE.

But a lot has happen when this book was written and recent EE version starting with 5, but especially 6 and 7 had made EE development even easier than Spring development.

So if you are thinking of choosing EE, you might wonder what EJB contributes with:

1. Pooling
2. Transaction
3. Security
4. Monitoring and Management
5. Asynchronous

Pooling

This makes accessing a EJB faster. Typically usage with Spring is to lazy inject things when a Business Object is requested.

Pooling is also a DOS protection since you cannot request endless number of Business Object. When the pool is empty of non busy EJB, the request will fail fast. This handling is important, since accepting new request when the server is overloaded will only worsen the situation.

Further sizing and resizing the pool and other pool is typically something a application administrator want to do after the deployment in production and this is done from unified interface in the EE container. No need to go in each application and know its inner configuration.

Transaction

Every public method will default start a new transaction if no one exists.

Security

The EE specification contains a good security API and is easy to use and covers all the EE components.

Since the EE 6 the EAR archive is history. Now EJB can be bundle in standard WAR archive.

And standard web.xml security is quite straight forward.

Monitoring and Management

With the emerge of DevOps (Development Operation) the monitoring and management has grown in importance (even though it always has been important).

All modern EE container has today this capability of monitoring and manage EJB as a standard.

Asynchronous

javax.ejb.Asynchronous was introduced in EE 6 and is easy to use. Example to make a method asynchronous:

@Stateless
public class OrderProcessorBean {

    // synchronous method
    public boolean validate(Order order) throws PaymentException {
        ...
    }

    @Asynchronous
    public Future<string> processPayment(Order order) throws PaymentException {
        ...
    }
}