Using the CDI API framework to implement the program driver programming mode
Using the CDI API framework to implement the program driver programming mode
Event -driven programming mode is a common software design mode. It realizes decoupled decoupled between the components of the software through the trigger and processing of the event.In the development of Java, with the help of ContenTs and Dependency Inject (CDI) API framework, we can easily implement the program -driven programming mode.
CDI is part of Javaee and can also be used in Javase.It provides a flexible mechanism to manage the dependence between JavaBeans and realize communication between components through the event mechanism.
Below we will introduce how to implement event -driven programming mode in the CDI framework.
First, we need to define an event.The incident is a simple POJO (ordinary Java object), which describes a specific state or action.For example, we can define an event called "Orderevent" to represent the creation of orders.
public class OrderEvent {
private String orderId;
public OrderEvent(String orderId) {
this.orderId = orderId;
}
public String getOrderId() {
return orderId;
}
}
Next, we need to create an event product.The event trigger is responsible for the event release event.We use CDI's `Event` type to define event triggers.
import javax.enterprise.inject.spi.CDI;
import javax.enterprise.event.Event;
public class OrderEventProducer {
private Event<OrderEvent> event;
public OrderEventProducer() {
CDI<Object> cdi = CDI.current();
event = cdi.getEvent();
}
public void createOrder(String orderId) {
OrderEvent orderEvent = new OrderEvent(orderId);
event.fire(orderEvent);
}
}
In the above example, we use the `cdi.current ()` method to obtain the current CDI container object, and use the `getevent ()` method to obtain the `Event` object.Then, we create an object and call the `Fire () method to publish an event.
Finally, we need to create an event listener to deal with the event.Event listener implements the CDI's `Observer` interface, and use the@observes` annotation to declare the type of event that needs to be received.
import javax.enterprise.event.Observes;
public class OrderEventListener {
public void onOrderCreated(@Observes OrderEvent event) {
String orderId = event.getOrderId();
// Processing the logic of the order creation event
System.out.println ("The order has been created:" + orderid);
}
}
In the above examples, the `OnorderCreated` method uses the`@observes` annotation to identify it as an event monitor and declare that the type of event it to be received is `Ordrevent`.
To enable CDI to automatically discover and manage event listeners, we also need to configure some additional CDI configurations in the code.The specific configuration method depends on the implementation of the use of CDI. For example, in Javaee, we can use the `Beans.xml` file to configure it.
Now, when we call the `Createorder ()" method of the `OrdereventProducer` to create an order, the event monitor` OrdereventListener `will automatically respond and handle the event.
public class Main {
public static void main(String[] args) {
OrderEventProducer producer = new OrderEventProducer();
producer.createOrder("12345");
}
}
In the above examples, we can see that when the method of calling the `Createorder ()` method creates an order, the method of the event monitor `OnorderCreated ()` method will be automatically called and output the information created by the order.
To sum up, using the CDI API framework to implement event -driven programming patterns can help us realize decoupling between software components and improve the maintenance of code and scalability.By defining events, creating event triggers, and writing incident monitors, we can easily achieve the release and processing of the event.
