SCALA Guice: The best practice of using the framework in the Java class library
SCALA Guice is a framework used in the Java library to achieve the characteristics of dependency injection and control reversal.In this article, we will introduce the best practice using Scala Guice, and provide some Java code examples.
1. What is SCALA Guice?
Scala Guice is the Scala version of Google Guice. It is a lightweight dependency injection framework.It allows developers to define dependency relationships by declaration and automatically inject dependent objects when the program is running.Scala Guice provides an elegant and type security way to solve the dependency relationship in the application and improve the testability and maintenance of the code.
2. The best practice of using Scala Guice
1. Definition dependency relationship
When using Scala Guice, you first need to define dependencies.You can declare the dependencies by using annotation or provider.
Example code:
scala
trait Greeting {
def sayHello(): Unit
}
class EnglishGreeting extends Greeting {
override def sayHello(): Unit = {
println("Hello!")
}
}
class ChineseGreeting extends Greeting {
override def sayHello(): Unit = {
Println ("Hello!")
}
}
class MyApp(greeting: Greeting) {
def start(): Unit = {
greeting.sayHello()
}
}
2. Definition module
Next, you need to define a module, which contains binding and configuration of dependencies.In the module, we can establish a dependency relationship by binding interfaces and specific implementation classes.
Example code:
scala
import com.google.inject.AbstractModule
class MyAppModule extends AbstractModule {
override def configure(): Unit = {
bind(classOf[Greeting]).to(classOf[EnglishGreeting])
// Or use @implementedby annotations to specify the default implementation:
bind(classOf[Greeting]).to(classOf[EnglishGreeting]).asEagerSingleton()
}
}
3. Create Injector
When using Scala Guice, we need to create an Injector object to initialize the dependent dependency injecting container.Injector will be responsible for managing dependency relationships and providing instantiated objects.
Example code:
scala
import com.google.inject.Guice
object MyAppRunner {
def main(args: Array[String]): Unit = {
val injector = Guice.createInjector(new MyAppModule)
val myApp = injector.getInstance(classOf[MyApp])
myApp.start()
}
}
4. Running program
Now, we can start the program by running the main method of MyApprunner.When the program is running, the Scala Guice will automatically inject instances of Greeting to the constructor of MyApp and execute the Sayhello method.
3. Conclusion
Using Scala Guice can help us manage and solve the dependency relationship in the Java class library more conveniently.This article introduces the best practice of Scala Guice and provides some example code to help understand.I hope this content will help you use Scala Guice in the Java library.
