Spring MVC Plugin Architecture

I am a novice with JavaEE but have some experience with ASP.NET MVC. With ASP.NET MVC, I know we can make a plugin architecture with ASP.NET MVC web app so you can make a dll with MVC structure and put it into the existing ASP.NET MVC web app to make it work without compiling the web app. http://www.wynia.o开发者_运维问答rg/wordpress/2008/12/05/aspnet-mvc-plugins/

I wonder if this kind of architecture is possible with Spring MVC. For example, when I make a jar (or war) file with MVC structure and put it into existing Spring MVC web app, it should work without recompiling the web app. If this is possible, how can I achieve that? Any reference would be appreciated.

It is possible without recompiling, but probably not without restarting. You could create a .jar which you drop into the WEB-INF/lib directory. By using classpath scanning you should be able to deploy your new controllers on start-up. You can skip the view entirely and directly output data to the ServletResponse. Rendering a view from a jar may or may not be possible, I don't know.

Sounds like you want to search for "hotdeploy".

What you are asking for is not a feature of Spring, but rather a feature of JVM and the application server. The application server is able to see that indeed your classes have changed and using some clever ClassLoader trickery it can load new versions to the runinng JVM as they become available. Java was not actually designed to work like this so there are some issues (ClassLoader, memory leak, hotdeploy are good keywords for finding more about the potential problems and possible solutions). I would not recommend this for production use but it can be handy during development.

Since this is a feature of the application servers, the actual details depend on the particular application server and are explained in it's documentation.

If you simply want some plugin-magic, not actual hotdeploy, there are other things you could do. A custom ClassLoader can load classes from whatever source (file, network, database..) you want and then you can instantiate and use these with reflection. (This is what happens when you deploy the war to Tomcat/JBoss or whatever). Accessing and dynamically reloading non-class resources inside jar/war files is way easier.