[Java] What is the difference between Tomcat, JBoss and Glassfish?
Tomcat is merely an HTTP server and Java servlet container. JBoss and GlassFish are full-blown Java EE application servers, including an EJB container and all the other features of that stack. On the other hand, Tomcat has a lighter memory footprint (~60-70 MB), while those Java EE servers weigh in at hundreds of megs. Tomcat is very popular for simple web applications, or applications using frameworks such as Spring that do not require a full Java EE server. Administration of a Tomcat server is arguably easier, as there are fewer moving parts.
However, for applications that do require a full Java EE stack (or at least more pieces that could easily be bolted-on to Tomcat)... JBoss and GlassFish are two of the most popular open source offerings (the third one is Apache Geronimo, upon which the free version of IBM WebSphere is built). JBoss has a larger and deeper user community, and a more mature codebase. However, JBoss lags significantly behind GlassFish in implementing the current Java EE specs. Also, for those who prefer a GUI-based admin system... GlassFish's admin console is extremely slick, whereas most administration in JBoss is done with a command-line and text editor. GlassFish comes straight from Sun/Oracle, with all the advantages that can offer. JBoss is NOT under the control of Sun/Oracle, with all the advantages THAT can offer.
I am starting to look into Enterprise Java and the book I am following mentions that it will use JBoss. Netbeans ships with Glassfish. I have used Tomcat in the past.
What are the differences between these three programs?
Both JBoss and Tomcat are Java servlet application servers, but JBoss is a whole lot more. The substantial difference between the two is that JBoss provides a full Java Enterprise Edition (Java EE) stack, including Enterprise JavaBeans and many other technologies that are useful for developers working on enterprise Java applications.
Tomcat is much more limited. One way to think of it is that JBoss is a Java EE stack that includes a servlet container and web server, whereas Tomcat, for the most part, is a servlet container and web server.
jboss and glassfish include a servlet container(like tomcat), however the two application servers (jboss and glassfish) also provide a bean container (and a few other things aswell I imagine)
It seems a bit discouraging to use Tomcat when you read these answers. However what most fail to mention is that you can get to identical or almost identical use cases with tomcat but that requires you to add the libraries needed (through Maven or whatever include system you use).
I have been running tomcat with JPA, EJBs with very small configuration efforts.