anton-liauchuk#11 use axon event handlers

README.md

@@ -104,7 +104,52 @@ Definition of common formats for API.
 ### 3.2. Communications between bounded contexts
 Communication between bounded contexts is asynchronous. Bounded contexts don't share data, it's forbidden to create a transaction which spans more than one bounded context.
 
-This solution reduces coupling of bounded contexts through data replication across contexts which results to higher bounded contexts independence.
+This solution reduces coupling of bounded contexts through data replication across contexts which results to higher bounded contexts independence. Event publishing/subscribing is used from Axon Framework. The example of implementation:
+```java
+@RequiredArgsConstructor
+@Component
+public class ApproveCourseProposalCommandHandler {
+
+    private final TransactionTemplate transactionTemplate;
+    private final CourseProposalRepository repository;
+    private final EventBus eventBus;
+
+    /**
+     * Handles approve course proposal command. Approves and save approved course proposal
+     *
+     * @param command command
+     * @throws ResourceNotFoundException              if resource not found
+     * @throws CourseProposalAlreadyApprovedException course proposal already approved
+     */
+    @CommandHandler
+    @PreAuthorize("hasRole('ADMIN')")
+    public void handle(ApproveCourseProposalCommand command) {
+        final CourseProposal proposal = transactionTemplate.execute(transactionStatus -> {
+            // the logic related to approving the proposal inside the transaction
+        });
+
+        final CourseProposalDTO dto = Objects.requireNonNull(proposal).toDTO();
+        // publishing integration event outside the transaction
+        eventBus.publish(GenericEventMessage.asEventMessage(new CourseApprovedByAdminIntegrationEvent(dto.getUuid())));
+    }
+}
+```
+
+The listener for this integration event:
+```java
+@Component
+@RequiredArgsConstructor
+public class SendCourseToApproveIntegrationEventHandler {
+
+    private final CommandGateway commandGateway;
+
+    @EventHandler
+    public void handleSendCourseToApproveEvent(SendCourseToApproveIntegrationEvent event) {
+        commandGateway.send(new CreateCourseProposalCommand(event.getCourseId()));
+    }
+
+}
+```
 
 ### 3.3. Validation
 Always valid approach is used. So domain model will be changed from one valid state to another valid state. Technically, validation rules are defined on `Command` models and executed during processing the command. Javax validation-api is used for defining the validation rules via annotations.
@@ -300,7 +345,7 @@ ArchUnit are used for implementing architecture tests. These tests are placed in
 **LayerTest** - tests for validating the dependencies between layers of application.
 
 ### 3.11. Axon Framework
-Axon Framework is used as DDD library for not creating custom building block classes.
+Axon Framework is used as DDD library for not creating custom building block classes. Also, more functionality for event publishing/event sourcing is used from Axon functionality.
 
 ### 3.12. Bounded context map
 ![](docs/bounded_context_map.png)

administration/application/src/main/java/com/educational/platform/administration/course/approve/ApproveCourseProposalCommandHandler.java

@@ -9,7 +9,8 @@
 import lombok.RequiredArgsConstructor;
 
 import org.axonframework.commandhandling.CommandHandler;
-import org.springframework.context.ApplicationEventPublisher;
+import org.axonframework.eventhandling.EventBus;
+import org.axonframework.eventhandling.GenericEventMessage;
 import org.springframework.security.access.prepost.PreAuthorize;
 import org.springframework.stereotype.Component;
 import org.springframework.transaction.support.TransactionTemplate;
@@ -26,7 +27,7 @@ public class ApproveCourseProposalCommandHandler {
 
     private final TransactionTemplate transactionTemplate;
     private final CourseProposalRepository repository;
-    private final ApplicationEventPublisher eventPublisher;
+    private final EventBus eventBus;
 
     /**
      * Handles approve course proposal command. Approves and save approved course proposal
@@ -52,6 +53,6 @@ public void handle(ApproveCourseProposalCommand command) {
         });
 
         final CourseProposalDTO dto = Objects.requireNonNull(proposal).toDTO();
-        eventPublisher.publishEvent(new CourseApprovedByAdminIntegrationEvent(dto, dto.getUuid()));
+        eventBus.publish(GenericEventMessage.asEventMessage(new CourseApprovedByAdminIntegrationEvent(dto.getUuid())));
     }
 }

administration/application/src/main/java/com/educational/platform/administration/course/create/SendCourseToApproveIntegrationEventListener.java → administration/application/src/main/java/com/educational/platform/administration/course/create/SendCourseToApproveIntegrationEventHandler.java

@@ -4,21 +4,19 @@
 import lombok.RequiredArgsConstructor;
 
 import org.axonframework.commandhandling.gateway.CommandGateway;
-import org.springframework.context.event.EventListener;
-import org.springframework.scheduling.annotation.Async;
+import org.axonframework.eventhandling.EventHandler;
 import org.springframework.stereotype.Component;
 
 /**
  * Event listener for {@link SendCourseToApproveIntegrationEvent}, executes the logic for creating course proposal by {@link CreateCourseProposalCommandHandler}.
  */
 @Component
 @RequiredArgsConstructor
-public class SendCourseToApproveIntegrationEventListener {
+public class SendCourseToApproveIntegrationEventHandler {
 
     private final CommandGateway commandGateway;
 
-    @Async
-    @EventListener
+    @EventHandler
     public void handleSendCourseToApproveEvent(SendCourseToApproveIntegrationEvent event) {
         commandGateway.send(new CreateCourseProposalCommand(event.getCourseId()));
     }

administration/application/src/main/java/com/educational/platform/administration/course/decline/DeclineCourseProposalCommandHandler.java

@@ -9,7 +9,8 @@
 import lombok.RequiredArgsConstructor;
 
 import org.axonframework.commandhandling.CommandHandler;
-import org.springframework.context.ApplicationEventPublisher;
+import org.axonframework.eventhandling.EventBus;
+import org.axonframework.eventhandling.GenericEventMessage;
 import org.springframework.security.access.prepost.PreAuthorize;
 import org.springframework.stereotype.Component;
 import org.springframework.transaction.support.TransactionTemplate;
@@ -26,7 +27,7 @@ public class DeclineCourseProposalCommandHandler {
 
     private final TransactionTemplate transactionTemplate;
     private final CourseProposalRepository repository;
-    private final ApplicationEventPublisher eventPublisher;
+    private final EventBus eventBus;
 
     /**
      * Handles decline course proposal command. Declines and save declined course proposal
@@ -52,7 +53,7 @@ public void handle(DeclineCourseProposalCommand command) {
         });
 
         final CourseProposalDTO dto = Objects.requireNonNull(proposal).toDTO();
-        eventPublisher.publishEvent(new CourseDeclinedByAdminIntegrationEvent(dto, dto.getUuid()));
+        eventBus.publish(GenericEventMessage.asEventMessage(new CourseDeclinedByAdminIntegrationEvent(dto.getUuid())));
     }
 
 }

administration/application/src/test/java/com/educational/platform/administration/course/approve/ApproveCourseProposalCommandHandlerTest.java

@@ -7,13 +7,14 @@
 import com.educational.platform.administration.integration.event.CourseApprovedByAdminIntegrationEvent;
 import com.educational.platform.common.exception.ResourceNotFoundException;
 import org.assertj.core.api.ThrowableAssert;
+import org.axonframework.eventhandling.EventBus;
+import org.axonframework.eventhandling.GenericEventMessage;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
-import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.test.util.ReflectionTestUtils;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.support.TransactionTemplate;
@@ -39,14 +40,14 @@ public class ApproveCourseProposalCommandHandlerTest {
     private TransactionTemplate transactionTemplate;
 
     @Mock
-    private ApplicationEventPublisher eventPublisher;
+    private EventBus eventBus;
 
     private ApproveCourseProposalCommandHandler sut;
 
     @BeforeEach
     void setUp() {
         transactionTemplate = new TransactionTemplate(transactionManager);
-        sut = new ApproveCourseProposalCommandHandler(transactionTemplate, repository, eventPublisher);
+        sut = new ApproveCourseProposalCommandHandler(transactionTemplate, repository, eventBus);
     }
 
     @Test
@@ -70,9 +71,9 @@ void handle_existingCourseProposal_courseProposalSavedWithStatusApproved() {
         assertThat(proposal)
                 .hasFieldOrPropertyWithValue("status", CourseProposalStatus.APPROVED);
 
-        final ArgumentCaptor<CourseApprovedByAdminIntegrationEvent> eventArgument = ArgumentCaptor.forClass(CourseApprovedByAdminIntegrationEvent.class);
-        verify(eventPublisher).publishEvent(eventArgument.capture());
-        final CourseApprovedByAdminIntegrationEvent event = eventArgument.getValue();
+        final ArgumentCaptor<GenericEventMessage<CourseApprovedByAdminIntegrationEvent>> eventArgument = ArgumentCaptor.forClass(GenericEventMessage.class);
+        verify(eventBus).publish(eventArgument.capture());
+        final CourseApprovedByAdminIntegrationEvent event = eventArgument.getValue().getPayload();
         assertThat(event)
                 .hasFieldOrPropertyWithValue("courseId", uuid);
     }

administration/application/src/test/java/com/educational/platform/administration/course/create/SendCourseToApproveIntegrationEventListenerTest.java → administration/application/src/test/java/com/educational/platform/administration/course/create/SendCourseToApproveIntegrationEventHandlerTest.java

@@ -16,19 +16,19 @@
 import static org.mockito.Mockito.verify;
 
 @ExtendWith(MockitoExtension.class)
-public class SendCourseToApproveIntegrationEventListenerTest {
+public class SendCourseToApproveIntegrationEventHandlerTest {
 
     @Mock
     private CommandGateway commandGateway;
 
     @InjectMocks
-    private SendCourseToApproveIntegrationEventListener sut;
+    private SendCourseToApproveIntegrationEventHandler sut;
 
     @Test
     void handleCourseApprovedByAdminEvent_approveCourseCommandExecuted() {
         // given
         final UUID uuid = UUID.fromString("123e4567-e89b-12d3-a456-426655440001");
-        final SendCourseToApproveIntegrationEvent event = new SendCourseToApproveIntegrationEvent(new Object(), uuid);
+        final SendCourseToApproveIntegrationEvent event = new SendCourseToApproveIntegrationEvent(uuid);
 
         // when
         sut.handleSendCourseToApproveEvent(event);

administration/application/src/test/java/com/educational/platform/administration/course/decline/DeclineCourseProposalCommandHandlerTest.java

@@ -4,16 +4,16 @@
 import com.educational.platform.administration.course.CourseProposalRepository;
 import com.educational.platform.administration.course.CourseProposalStatus;
 import com.educational.platform.administration.course.create.CreateCourseProposalCommand;
-import com.educational.platform.administration.integration.event.CourseDeclinedByAdminIntegrationEvent;
 import com.educational.platform.common.exception.ResourceNotFoundException;
 import org.assertj.core.api.ThrowableAssert;
+import org.axonframework.eventhandling.EventBus;
+import org.axonframework.eventhandling.GenericEventMessage;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
-import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.test.util.ReflectionTestUtils;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.support.TransactionTemplate;
@@ -39,14 +39,14 @@ public class DeclineCourseProposalCommandHandlerTest {
     private TransactionTemplate transactionTemplate;
 
     @Mock
-    private ApplicationEventPublisher eventPublisher;
+    private EventBus eventBus;
 
     private DeclineCourseProposalCommandHandler sut;
 
     @BeforeEach
     void setUp() {
         transactionTemplate = new TransactionTemplate(transactionManager);
-        sut = new DeclineCourseProposalCommandHandler(transactionTemplate, repository, eventPublisher);
+        sut = new DeclineCourseProposalCommandHandler(transactionTemplate, repository, eventBus);
     }
 
     @Test
@@ -70,9 +70,9 @@ void handle_existingCourseProposal_courseProposalSavedWithStatusDeclined() {
         assertThat(proposal)
                 .hasFieldOrPropertyWithValue("status", CourseProposalStatus.DECLINED);
 
-        final ArgumentCaptor<CourseDeclinedByAdminIntegrationEvent> eventArgument = ArgumentCaptor.forClass(CourseDeclinedByAdminIntegrationEvent.class);
-        verify(eventPublisher).publishEvent(eventArgument.capture());
-        final CourseDeclinedByAdminIntegrationEvent event = eventArgument.getValue();
+        var eventArgument = ArgumentCaptor.forClass(GenericEventMessage.class);
+        verify(eventBus).publish(eventArgument.capture());
+        var event = eventArgument.getValue().getPayload();
         assertThat(event)
                 .hasFieldOrPropertyWithValue("courseId", uuid);
     }

administration/integration-events/src/main/java/com/educational/platform/administration/integration/event/CourseApprovedByAdminIntegrationEvent.java

@@ -1,15 +1,14 @@
 package com.educational.platform.administration.integration.event;
 
 import lombok.Getter;
-import org.springframework.context.ApplicationEvent;
 
 import java.util.UUID;
 
 /**
  * Represents course approved by admin integration event, should be published after approval the course by admin.
  */
 @Getter
-public class CourseApprovedByAdminIntegrationEvent extends ApplicationEvent {
+public class CourseApprovedByAdminIntegrationEvent {
 
 
     private final UUID courseId;
@@ -18,12 +17,9 @@ public class CourseApprovedByAdminIntegrationEvent extends ApplicationEvent {
     /**
      * Create a new {@code CourseApprovedByAdminIntegrationEvent}.
      *
-     * @param source   the object on which the event initially occurred or with
-     *                 which the event is associated (never {@code null})
      * @param courseId course id
      */
-    public CourseApprovedByAdminIntegrationEvent(Object source, UUID courseId) {
-        super(source);
+    public CourseApprovedByAdminIntegrationEvent(UUID courseId) {
         this.courseId = courseId;
     }
 }

administration/integration-events/src/main/java/com/educational/platform/administration/integration/event/CourseDeclinedByAdminIntegrationEvent.java

@@ -1,15 +1,14 @@
 package com.educational.platform.administration.integration.event;
 
 import lombok.Getter;
-import org.springframework.context.ApplicationEvent;
 
 import java.util.UUID;
 
 /**
  * Represents course declined by admin integration event.
  */
 @Getter
-public class CourseDeclinedByAdminIntegrationEvent extends ApplicationEvent {
+public class CourseDeclinedByAdminIntegrationEvent {
 
 
     private final UUID courseId;
@@ -18,12 +17,9 @@ public class CourseDeclinedByAdminIntegrationEvent extends ApplicationEvent {
     /**
      * Create a new {@code CourseDeclinedByAdminIntegrationEvent}.
      *
-     * @param source   the object on which the event initially occurred or with
-     *                 which the event is associated (never {@code null})
      * @param courseId course id
      */
-    public CourseDeclinedByAdminIntegrationEvent(Object source, UUID courseId) {
-        super(source);
+    public CourseDeclinedByAdminIntegrationEvent(UUID courseId) {
         this.courseId = courseId;
     }
 }

course-enrollments/application/src/main/java/com/educational/platform/course/enrollments/register/RegisterStudentToCourseCommandHandler.java

@@ -8,7 +8,8 @@
 import lombok.RequiredArgsConstructor;
 
 import org.axonframework.commandhandling.CommandHandler;
-import org.springframework.context.ApplicationEventPublisher;
+import org.axonframework.eventhandling.EventBus;
+import org.axonframework.eventhandling.GenericEventMessage;
 import org.springframework.lang.NonNull;
 import org.springframework.security.access.prepost.PreAuthorize;
 import org.springframework.stereotype.Component;
@@ -29,8 +30,8 @@ public class RegisterStudentToCourseCommandHandler {
     private final TransactionTemplate transactionTemplate;
     private final CourseEnrollmentRepository courseEnrollmentRepository;
     private final CourseEnrollmentFactory courseEnrollmentFactory;
-    private final ApplicationEventPublisher eventPublisher;
     private final CurrentUserAsStudent currentUserAsStudent;
+    private final EventBus eventBus;
 
     /**
      * Creates course enrollment from command.
@@ -49,11 +50,8 @@ public UUID handle(RegisterStudentToCourseCommand command) {
         });
 
         final UUID uuid = Objects.requireNonNull(courseEnrollment).getUuid();
-
-        eventPublisher.publishEvent(
-                new StudentEnrolledToCourseIntegrationEvent(courseEnrollment,
-                        command.getCourseId(),
-                        currentUserAsStudent.userAsStudent().toReference()));
+        eventBus.publish(GenericEventMessage.asEventMessage(new StudentEnrolledToCourseIntegrationEvent(command.getCourseId(),
+                currentUserAsStudent.userAsStudent().toReference())));
 
         return uuid;
     }