One of the most important concepts that you need to know about Java EE is: it is a standard. If you go to the Java Community Process (JCP) website, you will find the Java Specification Request (JSR) for the Java EE platform (for Version 8 it is JSR 366).

A standard... for what? Well, for an application server! For instance, a Java EE application server.

It means that you can develop your Java EE application knowing it will run in an environment that provides a bunch of resources that you can rely on.

It also means you can easily move from one application server to another, as long as you stick to the Java EE patterns instead of some vendor-specific feature (considered a bad practice). Your application should have the same behavior no matter what Java EE-compatible server you are using.

Oh, yes! Beyond being a standard, Java EE is also a certification. For a Java EE server to be considered compatible, it has to pass through a number of tests to guarantee it implements every single point of the specification (JSR).

This amazing ecosystem allows for less coding of your application and gives you the chance to focus on what really matters to you or to your client. Without a standard environment, you would need to implement your own code for request/response management, queues, connection pooling, and other stuff.

You can definitely do it if you want, but you don't have to. Actually you can even write your own Java EE application server, if you want to.

Having said that let's move on with the chapter! In the following recipes, you are going to learn how to take advantage of some cool features already implemented on your favorite Java EE application server.

Examples will be based on GlassFish 5 but, as I mentioned before, they should have the same behavior for any other compatible implementation.