CODEWITHSUNDEEP
javajakarta-ee
Luciano Marti
Luciano Marti

Reputation: 45

Why are some Java EE APIs implemented in Java SE?

I've noticed recently about some APIs that are supposed to be part of Java EE, but seem to be implemented in Java SE. For example, there's JAX-WS, which is a Java EE API, but can be used completely in a Java SE project.

Is there anything I'm getting wrong? There are some APIs from Java EE implemented in Java SE out of the box? Where can I find information about what JEE APIs are available in JSE as well?

Upvotes: 1

Views: 306

Answers (1)

Renato
Renato

Reputation: 13690

Java SE APIs are basically the Java Standard Library. There's a nice diagram on the Java Platform Docs

And here is a list of the "Base Libraries": https://docs.oracle.com/javase/8/docs/technotes/guides/index.html#langutil

which includes java.lang, math, collections, reflection, concurrency, logging, preferences, io, net .... (notice that many of these are not even widely used by the Java community, like logging - where slf4j-api is the de-factor standard).

Then, there's also the "Integration Libraries" that include things like JDBC (Database Access) and JNDI (things like LDAP), and "User Interface Libraries" (used to be Swing and JavaFX, but now it's back to only Swing).

The Java EE APIs include many other things, like email and JAX-RS as you mention, which extend the Java libraries and in theory, should interact and work on top of the SE APIs, providing a comprehensive whole suited for enterprisey development.

They are not implemented by the JavaSE runtime!

However, each JavaEE API can be implemented independently by independent organisations (or anyone that has enough spare time to spend on the effort) and be used from a mostly Java SE application on their own. This is why there's lots of Servlet containers (Tomcat, Jetty, GlassFish and many others) available which implement the Servlet API and not much else!

It should be noted that quite recently, JavaEE has become officially the JakartaEE project. There's a searchable list of projects here.

I'd also like to mention there's another big set of APIs that were developed in parallel with JavaEE in the OSGi world, by the OSGi Alliance, that focussed on modularity of dynamic Java applications.

Finally, a competing framework, Spring is quite dominant in the Java world (and has actually influenced a lot the development of JavaEE itself), and even today, with beginner-friendly projects like Spring Boot is probably more popular than JavaEE itself!

Myself, I like to stick with only Java SE, a few EE APIs like Servlets and JDBC (EDIT: jdbc is in the standard lib!) for essentials, and community driven projects (see for example Micronaut and Vert.x) which are really cool stuff and are not based on any standards at all!

In summary, the Java world is big and there's a lot of variety! JavaEE is but a small part of it.

Upvotes: 1

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