Spring Container Queries

[Vaibhav Gargs]

Suppose we have a Spring MVC application running on Tomcat/WAS. I would like to understand

1. how the spring container is loaded ?

2. When is it loaded?


3. Can we have multiple instances of spring container?

[Tim Holloway]

As I said tou you here, I don't think I'd use the term "Container" for Spring. Spring is a provisioner and a configurator, and it supplies a number of frameworks, but the actual "container" for a webapp is the deployed WAR in the webapp server.

And since Spring is not a standard J2EE or JEE service provided by the container, that means that each webapp has to include Spring (or not) if it needs it as part of the WAR.

It's "loaded" as simply another set of classes the same way all classes are loaded. There's no Spring Thread or process, just a Factory that the application can draw upon whenever it needs a particular bean.

And the answer to your third question was given in the other message thread I mentioned.

[Peter Rooke]

You could start here; Spring Framework’s Inversion of Control (IoC) container.  

You could have many instances of the application context (IoC), but I'm not sure why would would do so.  If you wanted different configurations dependant upon runtime environments (for example for development, testing, live production) then springs profiles are designed to offer that functionality.    

Note that the term "container" has became one of the overused terms in computing.  It now has different meanings depending on the subject matter.  
The Spring IoC does not have much in common with other technologies that use the same term (like docker or JEE).  

[Tim Holloway]

Peter Rooke wrote:The Spring IoC does not have much in common with other technologies that use the same term (like docker or JEE).  

Which is why I don't like to call it a container, despite what the official docs say.

As containers go, it's a leaky one. Although technically it can manage beans over their entire lifecycle, in actuality a raw bean, once manufactured and returned to application code is mostly on its own.