CDI and the Java EE ecosystem

@Transactional @Interceptor
public class TransactionInterceptor {
   @Resource UserTransaction transaction;

   @AroundInvoke public Object manageTransaction(InvocationContext ctx) throws Exception { ... }
}

@SessionScoped
public class Login implements Serializable {
   @Inject Credentials credentials;
   @PersistenceContext EntityManager userDatabase;
    ...
}

public class LoginServlet extends HttpServlet {
   @Inject Credentials credentials;
   @Inject Login login;

   @Override
   public void service(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
      credentials.setUsername(request.getParameter("username")):
      credentials.setPassword(request.getParameter("password")):
      login.login();
      if ( login.isLoggedIn() ) {
         response.sendRedirect("/home.jsp");
      }
      else {
         response.sendRedirect("/loginError.jsp");
      }
   }

}

@Transactional @MessageDriven
public class ProcessOrder implements MessageListener {
   @Inject Inventory inventory;
   @PersistenceContext EntityManager em;

   public void onMessage(Message message) {
      ...
   }
}

import jakarta.jms.ConnectionFactory;
import jakarta.jms.Queue;

public class OrderResources {
   @Resource(name="jms/ConnectionFactory")
   private ConnectionFactory connectionFactory;

   @Resource(name="jms/OrderQueue")
   private Queue orderQueue;

   @Produces @Order
   public Connection createOrderConnection() throws JMSException {
    return connectionFactory.createConnection();
   }

   public void closeOrderConnection(@Disposes @Order Connection connection)
         throws JMSException {
      connection.close();
   }

   @Produces @Order
   public Session createOrderSession(@Order Connection connection)
         throws JMSException {
      return connection.createSession(true, Session.AUTO_ACKNOWLEDGE);
   }

   public void closeOrderSession(@Disposes @Order Session session)
         throws JMSException {
      session.close();
   }

   @Produces @Order
   public MessageProducer createOrderMessageProducer(@Order Session session)
         throws JMSException {
      return session.createProducer(orderQueue);
   }

   public void closeOrderMessageProducer(@Disposes @Order MessageProducer producer)
         throws JMSException {
      producer.close();
   }
}

@Inject Order order;
@Inject @Order MessageProducer producer;
@Inject @Order Session orderSession;

public void sendMessage() {
   MapMessage msg = orderSession.createMapMessage();
   msg.setLong("orderId", order.getId());
   ...
   producer.send(msg);
}

 import jakarta.enterprise.inject.spi.Extension;

class MyExtension implements Extension { ... }

org.mydomain.extension.MyExtension

@Inject
MyBean(MyExtension myExtension) {
   myExtension.doSomething();
}

import jakarta.enterprise.inject.spi.Extension;

class MyExtension implements Extension {

   void beforeBeanDiscovery(@Observes BeforeBeanDiscovery bbd) {
      Logger.global.debug("beginning the scanning process");
   }

   <T> void processAnnotatedType(@Observes ProcessAnnotatedType<T> pat) {
      Logger.global.debug("scanning type: " + pat.getAnnotatedType().getJavaClass().getName());
   }

   void afterBeanDiscovery(@Observes AfterBeanDiscovery abd) {
      Logger.global.debug("finished the scanning process");
   }

}

import jakarta.enterprise.inject.spi.Extension;

class MyExtension implements Extension {

   <T> void processAnnotatedType(@Observes @WithAnnotations({Ignore.class}) ProcessAnnotatedType<T> pat) {
      /* tell the container to ignore the type if it is annotated @Ignore */
      if ( pat.getAnnotatedType().isAnnotationPresent(Ignore.class) ) pat.veto();
   }

}

<T> void processAnnotatedType(@Observes ProcessAnnotatedType<T> pat, BeanManager beanManager) { ... }

void afterBeanDiscovery(@Observes AfterBeanDiscovery event, BeanManager beanManager) { ... }

@Inject BeanManager beanManager;

CDI.current().getBeanManager()

BeanManager manager = CDI.current().getBeanManager();

CDI.select(Foo.class).get()

import jakarta.enterprise.inject.spi.CDI;

...

//get the BeanManager
BeanManager beanManager = CDI.current().getBeanManager();

//CDI uses an AnnotatedType object to read the annotations of a class
AnnotatedType<SomeFrameworkComponent> type = beanManager.createAnnotatedType(SomeFrameworkComponent.class);

//The extension uses an InjectionTarget to delegate instantiation, dependency injection
//and lifecycle callbacks to the CDI container
InjectionTarget<SomeFrameworkComponent> it = beanManager.createInjectionTarget(type);

//each instance needs its own CDI CreationalContext
CreationalContext ctx = beanManager.createCreationalContext(null);

//instantiate the framework component and inject its dependencies
SomeFrameworkComponent instance = it.produce(ctx);  //call the constructor
it.inject(instance, ctx);  //call initializer methods and perform field injection
it.postConstruct(instance);  //call the @PostConstruct method

...

//destroy the framework component instance and clean up dependent objects
it.preDestroy(instance);  //call the @PreDestroy method
it.dispose(instance);  //it is now safe to discard the instance
ctx.release();  //clean up dependent objects

public interface BeanAttributes<T> {
   public Set<Type> getTypes();
   public Set<Annotation> getQualifiers();
   public Class<? extends Annotation> getScope();
   public String getName();
   public Set<Class<? extends Annotation>> getStereotypes();
   public boolean isAlternative();
}

public interface Bean<T> extends Contextual<T>, BeanAttributes<T> {
   public Class<?> getBeanClass();
   public Set<InjectionPoint> getInjectionPoints();
   public boolean isNullable();
}

Set<Bean<?>> allBeans = beanManager.getBeans(Object.class, new AnnotationLiteral<Any>() {});

import jakarta.enterprise.inject.spi.Extension;
import jakarta.enterprise.event.Observes;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import jakarta.enterprise.inject.spi.InjectionPoint;
...

public class FrameworkManagerExtension implements Extension {

    void afterBeanDiscovery(@Observes AfterBeanDiscovery event, BeanManager bm) {
        event.addBean()
           /* read annotations of the class and create an InjectionTarget used to instantiate the class and inject dependencies */
           .read(bm.createAnnotatedType(FrameworkManager.class))
           .beanClass(FrameworkManager.class)
           .scope(ApplicationScoped.class)
           .name("frameworkManager");
    }

}

import java.lang.reflect.Type;
import jakarta.enterprise.inject.spi.Extension;
import java.lang.annotation.Annotation;
...

public class QualifiedNameExtension implements Extension {

    <X> void processAnnotatedType(@Observes ProcessAnnotatedType<X> event) {

        /* wrap this to override the annotations of the class */
        final AnnotatedType<X> at = event.getAnnotatedType();

        /* Only wrap AnnotatedTypes for classes with @Named packages */
        Package pkg = at.getJavaClass().getPackage();
        if (pkg == null || !pkg.isAnnotationPresent(Named.class) ) {
            return;
        }

        String unqualifiedName = "";
        if (at.isAnnotationPresent(Named.class)) {
            unqualifiedName = at.getAnnotation(Named.class).value();
        }
        if (unqualifiedName.isEmpty()) {
            unqualifiedName = Introspector.decapitalize(at.getJavaClass().getSimpleName());
        }
        final String qualifiedName = pkg.getAnnotation(Named.class).value()
                            + '_' + unqualifiedName;

        event.configureAnnotatedType().remove((a) -> a.annotationType().equals(Named.class)).add(NamedLiteral.of(qualifiedName));
    }

}

import jakarta.enterprise.inject.spi.Extension;
import jakarta.enterprise.inject.Alternative;
...

class ServiceAlternativeExtension implements Extension {

   <T extends Service> void processAnnotatedType(@Observes ProcessAnnotatedType<T> event) {
      event.configureAnnotatedType().add(Alternative.Literal.INSTANCE);
   }
}

public interface BeanAttributes<T> {

   public Set<Type> getTypes();

   public Set<Annotation> getQualifiers();

   public Class<? extends Annotation> getScope();

   public String getName();

   public Set<Class<? extends Annotation>> getStereotypes();

   public boolean isAlternative();

}

public interface ProcessBeanAttributes<T> {

    public Annotated getAnnotated();

    public BeanAttributes<T> getBeanAttributes();

    public BeanAttributesConfigurator<T> configureBeanAttributes();

    public void setBeanAttributes(BeanAttributes<T> beanAttributes);

    public void addDefinitionError(Throwable t);

    public void veto();

}

public <T> BeanAttributes<T> createBeanAttributes(AnnotatedType<T> type);

public BeanAttributes<?> createBeanAttributes(AnnotatedMember<?> type);

firstName=Gavin
lastName=King

import jakarta.enterprise.event.Observes;
import jakarta.enterprise.inject.spi.Extension;
import jakarta.enterprise.inject.spi.InjectionPoint;

public class ConfigExtension implements Extension {

    <X> void processInjectionTarget(@Observes ProcessInjectionTarget<X> pit) {

          /* wrap this to intercept the component lifecycle */
         final InjectionTarget<X> it = pit.getInjectionTarget();

        final Map<Field, Object> configuredValues = new HashMap<Field, Object>();

        /* use this to read annotations of the class and its members */
        AnnotatedType<X> at = pit.getAnnotatedType();

        /* read the properties file */
        String propsFileName = at.getJavaClass().getSimpleName() + ".properties";
        InputStream stream = at.getJavaClass().getResourceAsStream(propsFileName);
        if (stream!=null) {

            try {
                Properties props = new Properties();
                props.load(stream);
                for (Map.Entry<Object, Object> property : props.entrySet()) {
                    String fieldName = property.getKey().toString();
                    Object value = property.getValue();
                    try {
                        Field field = at.getJavaClass().getDeclaredField(fieldName);
                        field.setAccessible(true);
                        if ( field.getType().isAssignableFrom( value.getClass() ) ) {
                            configuredValues.put(field, value);
                        }
                        else {
                            /* TODO: do type conversion automatically */
                            pit.addDefinitionError( new InjectionException(
                                   "field is not of type String: " + field ) );
                        }
                    }
                    catch (NoSuchFieldException nsfe) {
                        pit.addDefinitionError(nsfe);
                    }
                    finally {
                        stream.close();
                    }
                }
            }
            catch (IOException ioe) {
                pit.addDefinitionError(ioe);
            }
        }

        InjectionTarget<X> wrapped = new InjectionTarget<X>() {

            @Override
            public void inject(X instance, CreationalContext<X> ctx) {
                it.inject(instance, ctx);

                /* set the values onto the new instance of the component */
                for (Map.Entry<Field, Object> configuredValue: configuredValues.entrySet()) {
                    try {
                        configuredValue.getKey().set(instance, configuredValue.getValue());
                    }
                    catch (Exception e) {
                        throw new InjectionException(e);
                    }
                }
            }

            @Override
            public void postConstruct(X instance) {
                it.postConstruct(instance);
            }

            @Override
            public void preDestroy(X instance) {
                it.dispose(instance);
            }

            @Override
            public void dispose(X instance) {
                it.dispose(instance);
            }

            @Override
            public Set<InjectionPoint> getInjectionPoints() {
                return it.getInjectionPoints();
            }

            @Override
            public X produce(CreationalContext<X> ctx) {
                return it.produce(ctx);
            }

        };

        pit.setInjectionTarget(wrapped);

    }

}

public interface ProcessInjectionPoint<T, X> {
    public InjectionPoint getInjectionPoint();
    public InjectionPointConfigurator configureInjectionPoint();
    public void setInjectionPoint(InjectionPoint injectionPoint);
    public void addDefinitionError(Throwable t);
}

public interface AfterTypeDiscovery {
    public List<Class<?>> getAlternatives();
    public List<Class<?>> getInterceptors();
    public List<Class<?>> getDecorators();
    public void addAnnotatedType(AnnotatedType<?> type, String id);
}

public interface Context {
   public Class<? extends Annotation> getScope();
   public <T> T get(Contextual<T> contextual, CreationalContext<T> creationalContext);
   public <T> T get(Contextual<T> contextual);
   boolean isActive();
}

import jakarta.enterprise.context.spi.Context;

public interface AlterableContext extends Context {
    public void destroy(Contextual<?> contextual);
}