Merge pull request #13 from ralf-ueberfuhr-ars/features/interceptors

Introduce interceptors

src/main/java/de/sample/schulung/spring/blog/domain/BlogPostService.java

@@ -1,9 +1,9 @@
 package de.sample.schulung.spring.blog.domain;
 
+import de.sample.schulung.spring.blog.domain.interceptors.PublishEvent;
 import jakarta.validation.Valid;
 import jakarta.validation.constraints.NotNull;
 import lombok.RequiredArgsConstructor;
-import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.stereotype.Service;
 import org.springframework.validation.annotation.Validated;
 
@@ -17,7 +17,6 @@
 @RequiredArgsConstructor
 public class BlogPostService {
 
-  private final ApplicationEventPublisher eventPublisher;
   private final BlogPostSink sink;
 
   public long count() {
@@ -32,11 +31,10 @@ public Optional<BlogPost> findById(UUID id) {
     return sink.findById(id);
   }
 
+  @PublishEvent(BlogPostCreatedEvent.class)
   public void create(@Valid @NotNull BlogPost blogPost) {
     blogPost.setTimestamp(LocalDateTime.now());
     this.sink.create(blogPost);
-    this.eventPublisher.publishEvent(new BlogPostCreatedEvent(blogPost));
   }
 
-
 }

src/main/java/de/sample/schulung/spring/blog/domain/BlogPostSink.java

@@ -11,4 +11,9 @@ public interface BlogPostSink {
   Stream<BlogPost> findAll();
   Optional<BlogPost> findById(UUID id);
 
+  default void createAll(BlogPost... blogposts) {
+    Stream.of(blogposts)
+      .forEach(this::create);
+  }
+
 }

src/main/java/de/sample/schulung/spring/blog/domain/interceptors/PublishEvent.java

@@ -0,0 +1,21 @@
+package de.sample.schulung.spring.blog.domain.interceptors;
+
+import java.lang.annotation.*;
+
+/**
+ * Annotate a method to get an event fired after method execution.
+ */
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+@Inherited
+@Documented
+public @interface PublishEvent {
+
+  /**
+   * The event class. This class needs a constructor with the same parameters as the method.
+   *
+   * @return the event class
+   */
+  Class<?> value();
+
+}

src/main/java/de/sample/schulung/spring/blog/domain/interceptors/PublishEventInterceptor.java

@@ -0,0 +1,53 @@
+package de.sample.schulung.spring.blog.domain.interceptors;
+
+import org.aopalliance.intercept.MethodInterceptor;
+import org.springframework.aop.Pointcut;
+import org.springframework.aop.framework.autoproxy.AbstractBeanFactoryAwareAdvisingPostProcessor;
+import org.springframework.aop.support.DefaultPointcutAdvisor;
+import org.springframework.aop.support.annotation.AnnotationMatchingPointcut;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.stereotype.Component;
+
+@Component
+public class PublishEventInterceptor
+  extends AbstractBeanFactoryAwareAdvisingPostProcessor
+  implements InitializingBean {
+
+  private final MethodInterceptor publishEventAdvice;
+
+  public PublishEventInterceptor(final ApplicationEventPublisher eventPublisher) {
+    this.publishEventAdvice = invocation -> {
+      // create event object
+      Object event = null;
+      // find @PublishEvent annotation on invoked method
+      final var annotation = AnnotationUtils.findAnnotation(invocation.getMethod(), PublishEvent.class);
+      if(null != annotation) {
+        event = annotation.value() // event type
+          // event type must have a constructor with the same type as the invoked method
+          // service.create(blogPost) -> new BlogPostCreatedEvent(blogPost)
+          .getConstructor(invocation.getMethod().getParameterTypes())
+          .newInstance(invocation.getArguments());
+      }
+      // if something is wrong until here, we do not invoke the service's create-method
+      // now, we invoke the service
+      final var result = invocation.proceed();
+      // if an exception occured, the event is not fired
+      // now, we fire the event
+      if(null != event) {
+        eventPublisher.publishEvent(event);
+      }
+      // and we need to return the service's result to the invoker (the controller)
+      return result;
+    };
+  }
+
+  @Override
+  public void afterPropertiesSet() {
+    Pointcut pointcut = new AnnotationMatchingPointcut(null, PublishEvent.class, true);
+    this.advisor = new DefaultPointcutAdvisor(pointcut, publishEventAdvice);
+  }
+
+
+}

src/main/java/de/sample/schulung/spring/blog/persistence/JpaBlogPostSink.java

@@ -4,6 +4,7 @@
 import de.sample.schulung.spring.blog.domain.BlogPostSink;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Transactional;
 
 import java.util.Optional;
 import java.util.UUID;
@@ -29,6 +30,12 @@ public void create(BlogPost post) {
     mapper.copy(savedEntity, post);
   }
 
+  @Transactional
+  @Override
+  public void createAll(BlogPost... blogposts) {
+    BlogPostSink.super.createAll(blogposts);
+  }
+
   @Override
   public Stream<BlogPost> findAll() {
     return repo.findAll()

src/test/java/de/sample/schulung/spring/blog/boundary/BlogPostControllerTests.java

@@ -4,8 +4,6 @@
 import de.sample.schulung.spring.blog.domain.InMemoryBlogPostSink;
 import org.junit.jupiter.api.Test;
 import org.mapstruct.factory.Mappers;
-import org.mockito.Mockito;
-import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.http.HttpStatus;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -14,8 +12,7 @@ public class BlogPostControllerTests {
 
   @Test
   void shouldCreateBlogPostSuccessfully() {
-    final var eventPublisher = Mockito.mock(ApplicationEventPublisher.class);
-    final var service = new BlogPostService(eventPublisher, new InMemoryBlogPostSink());
+    final var service = new BlogPostService(new InMemoryBlogPostSink());
     final var mapper = Mappers.getMapper(BlogPostDtoMapper.class);
     final var controller = new BlogPostController(service, mapper);
     final var blogPost = new BlogPostDto();