Application cases of CDI API in the Java library
CDI (Contexts and Dependency Injection) is a dependent injection framework introduced by Java Ee 6 in Java Ee 6. It has the ability to decide and loosen the loose coupling of components in the commentary Java class.CDI API supports dependencies injection in the Java library, providing a flexible and scalable way to manage the dependency relationship between Bean.
Below is the application case of the CDI API in the Java class library:
Case 1: Dependent injection
CDI API allows us to use dependencies injected to manage objects in the Java library to manage the dependencies.For example, we can define a simple service interface and implementation class, and use the @Inject annotation to inject the implementation class into other classes.
public interface GreetingService {
void greet(String name);
}
@ApplicationScoped
public class SimpleGreetingService implements GreetingService {
public void greet(String name) {
System.out.println("Hello, " + name + "!");
}
}
public class GreetingController {
@Inject
private GreetingService greetingService;
public void greetUser(String name) {
greetingService.greet(name);
}
}
In the above example, we injected the SimplegreetingService class into the GreetingController class.In this way, we can use the GreetingService objects anywhere in the GreetingController class.
Case 2: Event trigger and monitoring
The CDI API also provides a mechanism for triggering and monitoring.We can define a custom event object, and then use the @Inject annotation to inject the event trigger into other classes.Other classes can be triggered to trigger events, and can monitor the event by adding an observer method.
public class OrderEvent {
private String orderId;
public OrderEvent(String orderId) {
this.orderId = orderId;
}
public String getOrderId() {
return orderId;
}
}
public class OrderProcessor {
@Inject
private Event<OrderEvent> orderEvent;
public void processOrder(String orderId) {
// Processing the logic of the order
orderEvent.fire(new OrderEvent(orderId));
}
}
public class OrderListener {
public void onOrderProcessed(@Observes OrderEvent event) {
// The logic after processing the order is completed
System.out.println ("The order has been processed:" + event.getOrderid ());
}
}
In the above example, the OrderProcessor class uses the Event object to trigger the OrderEvent event, and then the OrderListener class to monitor the incident by adding an observer method onORDERPROCESED.
Through the CDI API, we can easily implement the event release and subscription mode to perform specific operations or respond to specific events.
Summarize:
The application of CDI API in the Java library is very wide. It provides the characteristics of dependency injection, event triggering and monitoring, giving us greater flexibility and scalability to manage the dependent relationship between components.Through these characteristics, we can decouple the code and improve the testability of the code, and achieve more efficient business logic.
