Spring Framework - Integration with old Java webapp

I'm working on a 10-year-old Java webapp, and I would like to开发者_开发问答 introduce some new technology into the project. One of the things I would like to start doing is dependency injection. I know the Spring Framework has the capability to do dependency injection, but I am having a hard time integrating the framework into the old project.

Could someone provide an example of what I would have to change in my web.xml, other files I would have to add, and other changes I would need to make? I want the smallest Spring footprint while still being bale to do dependency injection.

There are a lot of examples online about starting a new project using Spring, but I can't find any about integrating Spring into an old project.

Thanks.

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You'll have to start by adding a context loader listener into your web.xml, along with the locations of the Spring configuration XML files.

You should configure the Spring DispatcherServlet to accept all URLs that you wish for it to handle.

You should write Controllers to bind and validate HTTP requests, call services, add data to ModelAndView for rendering, and map JSPs to success/failure views as needed.

You should put interfaces in front of your service and persistence tiers. Move implementations into implementation classes that Spring can inject.

Leverage Spring AOP for security and transactions and logging as needed.

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Throwing new technology at a project wont make it faster\better, unless you introduce the new technology to all parts of the project. The idea behind DI is to lose dependencies between objects. The project probably is tightly coupled, so you'd have to rewrite at least parts of the thing. Depending on the size, this can be a monster to beat - ask yourself if this is worth it, if it has any positive effect on the project other than introducing new technology.

The reason why there are little to none tutorials about integrating DI container into an old project is quite simple: it usually doesn't make any sense. Either you use the pattern in all places, or none at all. The bastard child that would be creating by mixing both would be a horror to maintain. I'd really advise you think about why you want to introduce a DI container into that 10 year project. Unless there is a real good reason for doing it (and you are happy with rewriting a lot of code) don't do it.