Dagger framework in the Java library explores
The Dagger framework is a dependent injection (Dependency Inject) framework widely used in the Java library.It simplifies the process of dependence in injection by running the time code generation technology, which improves the readability and maintenance of the code.In this article, we will explore the technical principles of the Dagger framework in the Java class library and provide some Java code examples to help readers better understand.
First, let's find out what dependency injection is.Dependent injection is a design pattern. By drawing the dependencies of the object out of the code, the decoupling between objects is achieved.This model allows us to define the dependence between objects and give these dependencies to a independent container to manage.The Dagger framework is exactly a dependent injection container.
Let's look at a simple example to illustrate the usage and technical principles of the Dagger framework.Suppose we have an interface `logger` and an implementation class` consoleLogger`, we want to use this log function in other categories.First of all, we need to define an annotation of dependence `@inject`:
import javax.inject.Inject;
public class ConsoleLogger implements Logger {
@Inject
public ConsoleLogger() {
// Construct function injection
}
// Other methods to implement the logger interface
}
Then, we need to declare a comment that indicates a dependent relationship in a class that uses the log function `@inject`:
import javax.inject.Inject;
public class SomeClass {
private final Logger logger;
@Inject
public SomeClass(Logger logger) {
this.logger = logger;
}
public void doSomething() {
logger.log("Doing something...");
}
}
Next, we need to create a Dagger component that will be responsible for creating and managing the dependence of all objects:
import dagger.Component;
@Component
public interface AppComponent {
SomeClass getSomeClass();
}
Finally, we need to use Dagger components at the entrance of the application to create the required object:
public class Main {
public static void main(String[] args) {
AppComponent component = DaggerAppComponent.create();
SomeClass someClass = component.getSomeClass();
someClass.doSomething();
}
}
In the above examples, we used the@inject` annotation to add the dependency to the `ConsoleLogger` and the` SOMEClass` class.In addition, we obtain an object that has been created through the method of Dagger component's `GetSomeClass ()` method.The Dagger framework will automatically create and manage dependencies, and inject the `Logger` object into the constructor of the` SomeClass` class.
To sum up, the technical principle of the Dagger framework in the Java class library is to generate code by annotating processors, thereby simplifying the process of dependence in injection.It uses the `@inject` annotation to mark the dependency relationship, and automatically create and manage the creation and injection of the management object.This design mode improves the readability and maintenance of the code, allowing us to better organize and manage the dependence of code.
