Jakarta CDI - Lab 1 - Basic part 1

In this lab, we will explore creating the first injection where the Vehicle interface into a single implementation Car.

1. Defining the interface

Steps

1. Open the 01-jakarta-ee project and navigate to the src/main/java
2. Create an interface called Vehicle in the expert.os.labs.persistence.cid.vehicle package

3. Add a method called move()

   Info

   The move() method represents the action of moving a vehicle. Any class implementing this interface must provide an implementation for this method.

Expected results

• Interface Vehicle created in the src/main/java at the expert.os.labs.persistence.cdi.vehicle

Solution

Click to see...

public interface Vehicle {

    void move();
}

2. Defining the class

Steps

1. Create a class called Car in the expert.os.labs.persistence.cid.vehicle package
2. Implements the Vehicle interface

3. Annotate the Car class with the @ApplicationScoped annotation from jakarta.enterprise.context package

   Info

   This annotation is commonly used in Jakarta EE (formerly Java EE) to define a class as an application-scoped bean. It means that only one instance of this class will be created and managed by the Jakarta EE container throughout the application's lifetime.

4. Declare a logger for this class

   Tip

   You can use the java.util.logging.Logger class

   private static final Logger LOGGER = Logger.getLogger(Car.class.getName());
   

5. Add a field called name of type String

6. Add a constructor to the class associating a random Sxtring to the name field

   Tip

   You can use the UUID.randomUUID().toString() method to generate a random String

7. Override the method move() by logging the name of the vehicle using the logger

Expected results

• Class Car implementing Vehicle created containing a method move()

Solution

Click to see...

import jakarta.enterprise.context.ApplicationScoped;

import java.util.Objects;
import java.util.UUID;
import java.util.logging.Logger;

@ApplicationScoped
public class Car implements Vehicle {

    private static final Logger LOGGER = Logger.getLogger(Car.class.getName());

    private final String name;

    public Car() {
        this.name = UUID.randomUUID().toString();
    }

    @Override
    public void move() {
        LOGGER.info("My car is moving. The car's name is: " + name);
    }
}

3. Explore the class usage

Steps

1. Create a class called AppVehicle in the expert.os.labs.persistence.cid package

2. Add the following code to the class

   import jakarta.enterprise.inject.se.SeContainer;
   import jakarta.enterprise.inject.se.SeContainerInitializer;
   
   public class AppVehicle {
   
       public static void main(String[] args) {
           try (SeContainer container = SeContainerInitializer.newInstance().initialize()) {
               Vehicle vehicle = container.select(Vehicle.class).get();
               vehicle.move();
   
               Car car = container.select(Car.class).get();
               car.move();
           }
       }
   }
   

3. Run the class

Expected results

• Two logs related to the move() method execution, one for the vehicle.move() and another from the car.move() showing:

  INFO: My car is moving. The car's name is: <<UUID>>
  

Solution

Click to see...

import jakarta.enterprise.inject.se.SeContainer;
import jakarta.enterprise.inject.se.SeContainerInitializer;

public class AppVehicle {

    public static void main(String[] args) {
        try (SeContainer container = SeContainerInitializer.newInstance().initialize()) {
            Vehicle vehicle = container.select(Vehicle.class).get();
            vehicle.move();

            Car car = container.select(Car.class).get();
            car.move();
        }
    }
}