Jakarta CDI - After Intermediate Lab 1

In this lab, we will explore the CDI decorator using Workers as the sample, and we will decorate it with a manager.

1. Create the LoggerProducer class

Steps

1. Create a new package called decorator in the expert.os.labs.persistence.cid package
2. Create an interface called Worker
3. Create the worker method which will set a job

Solution

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public interface Worker {

    String work(String job);
}

2. Create the Programmer Class

1. Create a class called Programmer in the expert.os.labs.persistence.cid.decorator package
2. Implements Worker and the method work()
   • the Consumer class is from the java.util.function package
3. Define a private attribute Logger from the java.util.logging package
4. In the method work(), return a String based on its job

Solution

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import jakarta.enterprise.context.ApplicationScoped;

import java.util.logging.Logger;

@ApplicationScoped
public class Programmer implements Worker {

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

    @Override
    public String work(String job) {
        return "A programmer has received a job, it will convert coffee in code: " + job;
    }
}

3. Create the Manager Class (Decorator)

Steps

1. Create a class called Manager in the expert.os.labs.persistence.cid.decorator package
2. Implements the Worker interface
3. Annotate the class with @Decorator from the jakarta.decorator package
4. Add a priority to the decorator using the @Priority from the jakarta.annotation package
   • the priority must be set as Interceptor.Priority.APPLICATION
5. Add a private field Worker annotating it with:
   • @Inject from the jakarta.inject package
   • @Delegate from the jakarta.decorator package
   • @Any from the jakarta.enterprise.inject package

Solution

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import jakarta.annotation.Priority;
import jakarta.decorator.Decorator;
import jakarta.decorator.Delegate;
import jakarta.enterprise.inject.Any;
import jakarta.inject.Inject;
import jakarta.interceptor.Interceptor;

@Decorator
@Priority(Interceptor.Priority.APPLICATION)
public class Manager implements Worker {

    @Inject
    @Delegate
    @Any
    private Worker worker;

    @Override
    public String work(String job) {
        return "A manager has received a job and it will delegate to a programmer -> " + worker.work(job);
    }
}

6. Create the app class

Steps

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

2. Add a main method

   public static void main(String[] args) {
   }
   

3. Set up a try-with-resources block, inside the main method, to manage the Jakarta EE SeContainer that is responsible for dependency injection and managing resources

   try (SeContainer container = SeContainerInitializer.newInstance().initialize()) {     
   }
   

4. Obtain the value of the Worker through the container instance

5. Define a work from the worker instance
6. Printout the work

Expected results

• The following output

  <the output you defined>
  

Solution

Click to see...

import expert.os.labs.persistence.cdi.decorator.Worker;
import jakarta.enterprise.inject.se.SeContainer;
import jakarta.enterprise.inject.se.SeContainerInitializer;

public class AppWorker {

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

            String work = worker.work("Just a single button");
            System.out.println("The work result: " + work);
        }
    }
}