Scala Guice: How to achieve dependency injection in the Java class library

Scala Guice (also known as "SCALANG" or "Scala dependency injection") is a powerful framework for relying in injecting in the Java library.This article will introduce the basic concepts, usage methods and example code of Scala Guice. ## What is dependent injection? Dependent injection is a design pattern that allows us to manage the dependencies between categories more flexibly.In traditional dependency management methods, categories usually create the dependent objects they need directly.However, this tight coupling method makes the relationship between classes very complicated and difficult to maintain. The dependency injection is transferred from the class to external containers by relying on the management responsibility of dependencies to reduce the coupling between classes.In this way, we can more conveniently create, replace and reuse the dependencies, thereby improving the maintenance and testability of the code. ## Why choose Scala Guice? SCALA Guice is developed based on Google Guice. It is a lightweight dependency injection framework for Java.Scala Guice uses the same dependency injection principle as Google Guice, and is optimized and adapted for the Scala language.It provides a set of powerful features that can make us more conveniently achieve dependent injection in the Java class library. The following are several reasons for selecting Scala Guice: 1. Elegant SCALA support: Scala Guice provides special support for the SCALA language, such as dependency injection to SCALA objects and functions. 2. Easy -to -use: Scala Guice has a simple and consistent API, allowing us to rely on the injecting configuration quickly and easily. 3. High scalability: Scala Guice allows us to create customized binders and modules to meet specific dependent injection needs. ## How to use SCALA Guice in the Java library? It is very simple to use Scala Guice to inject dependencies in the Java library.The following is the general step: ### Step 1: Add Scala Guice dependence First, we need to add the Scala Guice library to our project.We can easily add Scala Guice dependencies through building tools such as Maven or Gradle. <dependency> <groupId>net.codingwell</groupId> <artifactId>scala-guice_2.13</artifactId> <version>4.2.6</version> </dependency> ### Step 2: Definition dependency relationship Then we need to define the dependence between our class.Suppose we have a class named `userService`, which depends on the` userRepository` class.We can achieve dependency injection by injection in `userReserVice`. public class UserService { private UserRepository userRepository; @Inject public UserService(UserRepository userRepository) { this.userRepository = userRepository; } } ### Step 3: Configuration dependencies Next, we need to configure our dependence.We can create a module inherited from the `AbstractModule` and bind our dependence in it. public class MyModule extends AbstractModule { @Override protected void configure() { bind(UserRepository.class).to(UserRepositoryImpl.class); } } ### Step 4: Create a dependent injectioner Finally, we need to create a dependent injectioner to obtain instances we need through it. public class MyApp { public static void main(String[] args) { Injector injector = Guice.createInjector(new MyModule()); UserService userService = injector.getInstance(UserService.class); // Use useervice ... } } Now, we can use the `UseRSERVICE` class without explicitly creating the` userRepository` instance it depends on.Scala Guice will automatically handle the injection of dependencies. ## Summarize This article introduces the basic concepts, usage methods and example code of Scala Guice.By using Scala Guice, we can more conveniently achieve dependent injection in the Java class library, thereby improving the maintenance and testability of the code.I hope this article can help you understand and use Scala Guice.