The role and principle of Javax Inject Note
The role and principle of Javax Inject Note
Javax Inject is one of the annotations used in Java to depend on injection, and it is very commonly used when realizing dependency injection.Dependent injection is a design model that is used to manage the dependency relationship between the objects. It determines the dependency relationship between the objects through external configuration, thereby achieving a loose coupling code design.
The role of Javax Inject comments is to inform the dependencies of injecting containers, and a certain class or field needs to be injected.The container can be automatically discovered and created by the injecting object through the mark, and it is injected into the place that needs to be dependent.Using Javax Inject annotations can make the code more concise and flexible, and improve maintainability and testability.
The principle of Javax Inject comments is achieved by dependent injection containers.There are two main components of dependent injection containers: component scanners and dependent injectionters.
The component scanner is responsible for scanning the project of the Javax Inject annotations and registered it into the container.It is generally implemented through the reflection mechanism. According to the annotation information of the class, find the dependencies that need to be injected and encapsulate it as an object.
The dependencies are responsible for injecting objects into places where dependencies are needed according to the dependent relationship.It first obtains the object that needs to be injected in the facilities, and then injects it into the target class through reflection or setter method.The container can adopt different injection methods according to the different annotations, such as the constructor injection, the setter method injection, or field injection.
The following is a simple example code, which shows how to use Javax inject annotations to achieve dependency injection:
public interface MessageService {
void sendMessage(String message);
}
public class EmailService implements MessageService {
@Override
public void sendMessage(String message) {
System.out.println("Sending email: " + message);
}
}
public class SMSNotification {
@Inject
private MessageService messageService;
public void sendSMS(String message) {
messageService.sendMessage("Sending SMS: " + message);
}
}
public class Main {
public static void main(String[] args) {
SMSNotification notification = new SMSNotification();
Injector injector = Guice.createInjector();
injector.injectMembers(notification);
notification.sendSMS("Hello!");
}
}
In the above example, EmailService implements the MESSAGESERVICE interface and uses the Javax Inject annotation.The SMSNotification class uses @inject annotations to mark the field of MESSAGESERVICE type, indicating that this field needs to be injected and dependent.In the main class, we use Guice to create a dependent injection container and use the Injector.injectMembers () method to depend inject the SMSNotification object.Finally, when calling the notification.sendsms () method, the messageService injection is automatically triggered and sending text messages.
In general, the Javax Inject Note is very useful when realizing dependency injection, which can simplify the code and improve the code's maintenance and testability.By relying on the help of injection containers, using the Javax Inject annotation can achieve automatic injection between objects, and to achieve loose -coupled code design.
