At its core, the Java Enterprise Edition (Java EE), formerly known as J2EE, is a collection of abstract, standardized specifications that prescribe solutions to commonly faced challenges in software development.
It is important to note the word abstract in this definition. This means that Java EE is simply a set of interfaces and contracts that provide a public-facing API for developers.
These abstract specs are also said to be standardized. What does that mean? It means that the entire collection of Java EE APIs are published according to well-defined criteria set by experts in the subject field of the API1.
By standardized, it also means that every Java EE API has gone through the rigorous process of the Java Community Process’s Java Spec Request program. The result of this process is a set of APIs that are industry-tried and -tested and are deemed to be here to stay.
However, remember that I said Java EE is abstract, right? Well, even though you will generally code against the Java EE APIs in the javax.* packages, you can’t run your application on Java EE per se.
How Do You Run a Java EE App?
To run a Java EE application, you need a concrete implementation of the Java EE spec. Remember that they are abstract. The official name given to the concrete implementation of Java EE is an application server. I bet you have heard that phrase before, right?
An application server is basically a concrete implementation of the Java EE abstract specs. This means that you run your application code using Java EE API implementations on an application server.
There are many application servers out there, including Payara Server, Apache TomEE, JBoss Wildfly, and IBM OpenLiberty, among others.
Footnotes