Dependency injection as a principal is quite easy. The consumer doesn’t provide/instantiates the dependency itself, but it’s rather passed in. Applying the pattern correctly to write better code or using DI frameworks is quite hard. Especially if you already have a code base. More on reddit.com

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I have an example project implemented with a variety of DI frameworks if you want concrete code samples: Avaje Dagger 2 Dirk Feather Guice Glassfish HK2 Inverno Jaywire JBock Spring Weld I have an opinion post in the same repo with shorter descriptions and samples. Anyways my take on the items listed: Dagger 2: Speed is very nice to have, but unless you're running on a toaster, the speed of DI frameworks handling things like constructor injection is not noticeable. Dagger 2 operates off of generated code and thus will be the fastest since there are no reflective lookups or excessive checks needed at runtime. Personally, I find the need to rebuild a project to reference these classes in my IDE a bit annoying. Dirk: Dirk is probably the most feature rich DI framework for its size, and even offers some CDI capabilities if you need them (But it is not fully CDI complaint). Configuring it is almost entirely automatic which is is a plus for lazy developers like me. Another great thing dirk does is the wonderful documentation on its project page README. Its top notch stuff. Feather: If file size is your concern, feather is your guy. Its like Guice if you stripped out all the extra stuff, just keeping barely enough to be JSR-330 compliance. Guice: If you want a bit more configurability on top of what is just required for JSR-330 compliance check out the github wiki page on Guice. It also has examples on how to integrate with some common frameworks like OSGI and struts. Jaywire: Its 100% manual. Don't. Spring: Really only viable if you're building a spring boot application. I've not looked too much in depth to Spring's DI so I can't give a great summary of it. Even though JSR-330 interop is scheduled for v3 you can get support immediately via includeFilters on the @ComponentScan. (Edited comment here) Replies have pointed out some differences in how it handles scope than I originally listed here. Weld: If you need more than just plain injection, namely scoped injection via CDI Weld is great. You don't need a whole SE environment to run a weld instance as they offer a stand-alone artifact. I don't write web-apps so I don't use built in scopes like RequestScoped but instead utilize CDI's ability to create custom scopes. That and extensions/interceptors to handle some automated work on injectable types. Choosing a DI framework is like choosing any other library. You choose the right tool for the job. They all have their pro's and con's. More on reddit.com

Please ensure that: Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions You include any and all error messages in full You ask clear questions You demonstrate effort in solving your question/problem - plain posting your assignments is forbidden (and such posts will be removed) as is asking for or giving solutions. Trying to solve problems on your own is a very important skill. Also, see Learn to help yourself in the sidebar If any of the above points is not met, your post can and will be removed without further warning. Code is to be formatted as code block (old reddit: empty line before the code, each code line indented by 4 spaces, new reddit: https://i.imgur.com/EJ7tqek.png ) or linked via an external code hoster, like pastebin.com, github gist, github, bitbucket, gitlab, etc. Please, do not use triple backticks (```) as they will only render properly on new reddit, not on old reddit. Code blocks look like this: public class HelloWorld { public static void main(String[] args) { System.out.println("Hello World!"); } } You do not need to repost unless your post has been removed by a moderator. Just use the edit function of reddit to make sure your post complies with the above. If your post has remained in violation of these rules for a prolonged period of time (at least an hour), a moderator may remove it at their discretion. In this case, they will comment with an explanation on why it has been removed, and you will be required to resubmit the entire post following the proper procedures. To potential helpers Please, do not help if any of the above points are not met, rather report the post. We are trying to improve the quality of posts here. In helping people who can't be bothered to comply with the above points, you are doing the community a disservice. I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns. More on reddit.com