In -depth interpretation of the principle of implementation of Dagger framework technology in the Java class library
In -depth interpretation of the principle of implementation of Dagger framework technology in the Java class library
Dagger is a dependencies injection, developed by Google and used to manage dependency relationships in Java applications.Dagger's design concept is to automatically generate code to reduce manual writing and maintain the workload of relying on the injection code.This article will deeply interpret the technical implementation principle of the Dagger framework and provide Java code examples for description.
In the traditional dependency injection framework, we usually need to manually configure dependency and provide corresponding injection points.This approach will lead to increased code coupling and increased maintenance costs.Dagger automated these tasks by using annotations and automatically generating code.
In Dagger, we must first define the dependencies of the injection object, that is, Module.The Module class uses @module annotations to mark, where the method is used to provide dependent objects by using @Provides annotations.The following is a simple module example:
@Module
public class MyModule {
@Provides
public MyDependency provideMyDependency() {
return new MyDependency();
}
}
In the above examples, the MyModule class uses @Module annotations to mark, and the PROVIDEMYDEPENDENCY method uses @Provides annotations to provide MyDependency objects.This means that when the MyDependency object is needed, Dagger will automatically call this method to provide an instance of the object.
Next, we need to mark places where need to be injected.This can be achieved through @Inject annotations.The following is a simple example:
public class MyClass {
@Inject
MyDependency myDependency;
public void doSomething() {
myDependency.doSomething();
}
}
In the above example, we can see that the MyDependency field in the MyClass class is marked by @Inject Note.This means that when creating MyClass objects, Dagger will automatically inject the MyDependency object.
In order to use Dagger, we also need a component class to coordinate the process of dependence in injection.We can think of the Component class as a bridge between the Module and the need to rely on injects.The following is a simple example:
@Component(modules = MyModule.class)
public interface MyComponent {
void inject(MyClass myClass);
}
In the above example, we can see that the Mycomponent interface uses the @Component annotation mark and specify the Module class through the Modules property.The Inject method is used to inject dependencies into the MyClass object.
In order to use Dagger, we need to create Mycomponent objects in the application entry point and call the corresponding injection method.The following is a simple example:
public class Main {
public static void main(String[] args) {
MyComponent component = DaggerMyComponent.create();
MyClass myClass = new MyClass();
component.inject(myClass);
myClass.doSomething();
}
}
In the above example, we created the Mycomponent object through the DaggerMycomPonent.create () method and injected the object into the MyClass instance.We then call MyClass's Dosomething method to perform the corresponding operation.
By using the DAGGER framework, we can improve the efficiency of dependency injection and reduce manual writing and maintaining the workload of relying on the injection code.The principle of Dagger's technical implementation is to use annotations and automatic generating code to achieve dependency injection.Through @module annotations to provide an example of dependent objects, through the @Inject annotation marking dependent object that needs to be injected, and to create a component class to coordinate the dependent injection process through the @Component annotation of the component class.
To sum up, the technical implementation principle of the Dagger framework is to automatically generate code to reduce the workload of manual writing and maintaining dependency injecting code, thereby improving the efficiency of dependence injection.Through annotations and component categories, we can easily define dependency relationships and provide injection points to make the code more modular and maintained.
