The latest articles on DEV Community by Sergey Volkodav (@volkodavs). https://dev.to/volkodavs https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F360636%2Fa4a646a4-4968-402c-a48c-8d2224538a67.png https://dev.to/volkodavs en Sergey Volkodav Sat, 04 Apr 2020 13:58:02 +0000 https://dev.to/volkodavs/dropwizard-dependency-injection-di-frameworks-54jf https://dev.to/volkodavs/dropwizard-dependency-injection-di-frameworks-54jf <h1> Introduction </h1> <p>Dropwizard does not provide dependency injection (DI) out of the box, which makes the developer free to choose the DI framework he likes. </p> <p>Dependency injection is a technique whereby one object supplies the dependencies of another object. A dependency is an object that can be used (a service).</p> <h2> Benefits </h2> <ul> <li>Helps in Unit testing </li> <li>Boilerplate code is reduced, as initializing of dependencies is done by the injector component</li> <li>Extending the application becomes easier</li> <li>It helps to enable loose coupling, which is important in application programming</li> </ul> <h2> Disadvantages </h2> <ul> <li>It’s a bit complex to learn, and if overused can lead to management issues and other problems</li> <li>Сompile-time errors are pushed to run-time</li> <li>Most of Dependency injection frameworks implemented with reflection</li> <li>This can hinder the use of IDE automation, such as “find references”, “show call hierarchy” and safe refactoring</li> </ul> <h2> Dependency injection types </h2> <ul> <li> <strong>constructor injection:</strong> the dependencies are provided through a class constructor. </li> <li> <strong>setter injection:</strong> the client exposes a setter method that the injector uses to inject the dependency</li> <li> <strong>interface injection:</strong> the dependency provides an injector method that will inject the dependency into any client passed to it. Clients must implement an interface that exposes a setter method that accepts the dependency</li> </ul> <h1> Options </h1> <ul> <li>Vanilla Java</li> <li>Google Guice</li> <li>Dagger</li> </ul> <h2> Vanilla Java </h2> <p>The process to manage dependencies manually requires extra work and harms code legibility. </p> <h3> Advantages </h3> <ul> <li>No third-party dependency</li> <li>Application start time is not affected</li> <li>Type-safe idiomatic configuration</li> <li>There is more traceability to the code when not using a DI framework since we know exactly where the instance is coming from.</li> </ul> <h3> Disadvantages </h3> <ul> <li>Building object graphs by hand are labor-intensive, error-prone, and makes testing difficult.</li> <li>Hard to maintain </li> <li>Leaky abstractions</li> </ul> <h2> Google Guice </h2> <p>Guice is an open-source software framework for the Java platform released by Google under the Apache License. It provides support for dependency injection using annotations to configure Java objects. </p> <p>Google Guice is fairly simple to use and will help with the maintainability of the code. It’s also possible to scan a whole package of classes to inject them.</p> <h3> Advantages </h3> <ul> <li>Support JSR-330 annotations</li> <li>Mature functionality </li> <li>Auto-scanning functionality </li> <li>Lightweight</li> <li>Support multiple scopes</li> <li>Type-safe idiomatic configuration</li> <li>A lot of guidance and best practices</li> <li>Very clean implementation of constructor Injection</li> <li>It encourages the use of interfaces and well-defined API’s</li> <li>Large community ~9.1K starts on Github, and &gt;10K posts on Stackoverflow </li> </ul> <h3> Disadvantages </h3> <ul> <li>Use java reflection for dependency lookup, but you can avoid it by providing manually instance </li> <li>Extra third party dependency </li> </ul> <h3> Dropwizard Guice extension </h3> <ul> <li>Hubspot: <a href="https://github.com/HubSpot/dropwizard-guice">https://github.com/HubSpot/dropwizard-guice</a> </li> <li>Intercom: <a href="https://github.com/intercom/dropwizard-guice">https://github.com/intercom/dropwizard-guice</a> </li> </ul> <h2> Google Dagger </h2> <p>Dagger is a fully static, compile-time dependency injection framework for both Java and Android. It is an adaptation of an earlier version created by Square and now maintained by Google.</p> <p>Dagger requires more work with code due to be a compile-time dependency injection framework but also gains in boot time since there is no need to use reflection. </p> <h3> Advantages </h3> <ul> <li>Support JSR-330 annotations </li> <li>Supposedly faster than Guice, because Dagger works by generating code up-front, whereas Guice uses Reflection at runtime.</li> <li>Optional maven compiler plugin can flag various errors at compile-time, which can be extremely useful.</li> <li>Detect cyclic dependenciesDetect unused and duplicate bindings. </li> <li>Detect incomplete modules (that don’t provide all bindings required to construct the object graph)</li> <li>Simpler API compared to Guice</li> </ul> <h3> Disadvantages </h3> <ul> <li>Limited API compared to Guice</li> <li>Overly restrictive</li> <li>Dagger will not inject objects that are not annotated with @Inject. May a problem when you dealing with 3rd party libraries</li> <li>Young compares to other DI frameworks </li> <li>Extra third party dependency </li> </ul> <p>Most dependency injectors rely on reflection to create and inject dependencies. Reflection is awesome, but is very time-consuming on low-end devices, and especially on old android versions. Dagger, however, uses a pre-compiler that creates all the classes it needs to work. That way, no reflection is needed. Dagger is less powerful than other dependency injectors, but it’s the most efficient.</p> <h1> Summary </h1> <p>Consider all three options I believe that Google Guice is the preferable option as a DI framework for Dropwizard because it will allow the developer to focus on functional requirements. Google Guice supports JSR-330 standardizes annotations that make the replacement of DI Framework easier if we decide to do that in the future. </p> <h1> References </h1> <ul> <li><a href="https://github.com/google/guice/wiki">https://github.com/google/guice/wiki</a></li> <li><a href="https://www.journaldev.com/2403/google-guice-dependency-injection-example-tutorial">https://www.journaldev.com/2403/google-guice-dependency-injection-example-tutorial</a></li> <li><a href="https://www.programcreek.com/java-api-examples/?api=com.hubspot.dropwizard.guice.GuiceBundle">https://www.programcreek.com/java-api-examples/?api=com.hubspot.dropwizard.guice.GuiceBundle</a></li> <li><a href="https://www.baeldung.com/guice">https://www.baeldung.com/guice</a></li> <li><a href="https://dagger.dev/users-guide">https://dagger.dev/users-guide</a></li> <li><a href="https://dzone.com/articles/dagger-2-tutorial-dependency-injection-made-easy">https://dzone.com/articles/dagger-2-tutorial-dependency-injection-made-easy</a></li> </ul> dropwizard