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Publish Order Created Event using Outbox Pattern
Explain the challenge of implementing "database operations and sending a message" as a single atomic operation. Explain how "Outbox Pattern" tries to solve this problem. Create order_events table, Entity, Repository, Service Create order even models Implement Order Event Mapper Store Order events into order_events table Create a Scheduled Job to publish order events to RabbitMQ
1 parent b775f8f commit a47b369

14 files changed

+326
-56
lines changed

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/OrderServiceApplication.java

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@@ -3,9 +3,11 @@
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import org.springframework.boot.SpringApplication;
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import org.springframework.boot.autoconfigure.SpringBootApplication;
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import org.springframework.boot.context.properties.ConfigurationPropertiesScan;
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import org.springframework.scheduling.annotation.EnableScheduling;
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@SpringBootApplication
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@ConfigurationPropertiesScan
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@EnableScheduling
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public class OrderServiceApplication {
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public static void main(String[] args) {

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/domain/OrderEventEntity.java

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package com.codebykavindu.bookstore.orders.domain;
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import com.codebykavindu.bookstore.orders.domain.models.OrderEventType;
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import jakarta.persistence.Column;
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import jakarta.persistence.Entity;
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import jakarta.persistence.EnumType;
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import jakarta.persistence.Enumerated;
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import jakarta.persistence.GeneratedValue;
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import jakarta.persistence.GenerationType;
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import jakarta.persistence.Id;
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import jakarta.persistence.SequenceGenerator;
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import jakarta.persistence.Table;
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import java.time.LocalDateTime;
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/**
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* @author Kavindu Perera
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*/
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@Entity
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@Table(name = "order_events")
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class OrderEventEntity {
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@Id
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@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "order_event_id_generator")
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@SequenceGenerator(name = "order_event_id_generator", sequenceName = "order_event_id_seq")
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private Long id;
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@Column(nullable = false)
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private String orderNumber;
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@Column(nullable = false, unique = true)
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private String eventId;
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@Enumerated(EnumType.STRING)
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private OrderEventType eventType;
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@Column(nullable = false)
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private String payload;
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@Column(name = "created_at", nullable = false, updatable = false)
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private LocalDateTime createdAt = LocalDateTime.now();
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@Column(name = "updated_at")
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private LocalDateTime updatedAt;
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public Long getId() {
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return id;
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}
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public void setId(Long id) {
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this.id = id;
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}
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public String getOrderNumber() {
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return orderNumber;
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}
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public void setOrderNumber(String orderNumber) {
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this.orderNumber = orderNumber;
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}
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public String getEventId() {
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return eventId;
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}
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public void setEventId(String eventId) {
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this.eventId = eventId;
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}
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public OrderEventType getEventType() {
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return eventType;
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}
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public void setEventType(OrderEventType eventType) {
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this.eventType = eventType;
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}
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public String getPayload() {
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return payload;
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}
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public void setPayload(String payload) {
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this.payload = payload;
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}
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public LocalDateTime getCreatedAt() {
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return createdAt;
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}
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public void setCreatedAt(LocalDateTime createdAt) {
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this.createdAt = createdAt;
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}
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public LocalDateTime getUpdatedAt() {
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return updatedAt;
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}
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public void setUpdatedAt(LocalDateTime updatedAt) {
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this.updatedAt = updatedAt;
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}
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}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/domain/OrderEventMapper.java

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package com.codebykavindu.bookstore.orders.domain;
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import com.codebykavindu.bookstore.orders.domain.models.OrderCreatedEvent;
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import com.codebykavindu.bookstore.orders.domain.models.OrderItem;
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import java.time.LocalDateTime;
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import java.util.Set;
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import java.util.UUID;
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import java.util.stream.Collectors;
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/**
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* @author Kavindu Perera
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*/
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class OrderEventMapper {
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private OrderEventMapper() {}
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static OrderCreatedEvent buildOrderCreatedEvent(OrderEntity order) {
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return new OrderCreatedEvent(
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UUID.randomUUID().toString(),
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order.getOrderNumber(),
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getOrderItems(order),
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order.getCustomer(),
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order.getDeliveryAddress(),
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LocalDateTime.now());
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}
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private static Set<OrderItem> getOrderItems(OrderEntity order) {
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return order.getItems().stream()
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.map(item -> new OrderItem(item.getCode(), item.getName(), item.getPrice(), item.getQuantity()))
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.collect(Collectors.toSet());
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}
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}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/domain/OrderEventPublisher.java

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package com.codebykavindu.bookstore.orders.domain;
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import com.codebykavindu.bookstore.orders.ApplicationProperties;
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import com.codebykavindu.bookstore.orders.domain.models.OrderCreatedEvent;
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import org.springframework.amqp.rabbit.core.RabbitTemplate;
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import org.springframework.stereotype.Component;
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/**
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* @author Kavindu Perera
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*/
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@Component
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class OrderEventPublisher {
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private final RabbitTemplate rabbitTemplate;
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private final ApplicationProperties properties;
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OrderEventPublisher(RabbitTemplate rabbitTemplate, ApplicationProperties properties) {
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this.rabbitTemplate = rabbitTemplate;
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this.properties = properties;
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}
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public void publish(OrderCreatedEvent event) {
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this.send(properties.newOrdersQueue(), event);
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}
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private void send(String routingKey, Object payload) {
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rabbitTemplate.convertAndSend(properties.orderEventsExchange(), routingKey, payload);
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}
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}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/domain/OrderEventRepository.java

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package com.codebykavindu.bookstore.orders.domain;
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import org.springframework.data.jpa.repository.JpaRepository;
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/**
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* @author Kavindu Perera
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*/
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interface OrderEventRepository extends JpaRepository<OrderEventEntity, Long> {}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/domain/OrderEventService.java

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package com.codebykavindu.bookstore.orders.domain;
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import com.codebykavindu.bookstore.orders.domain.models.OrderCreatedEvent;
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import com.codebykavindu.bookstore.orders.domain.models.OrderEventType;
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import com.fasterxml.jackson.core.JsonProcessingException;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import java.util.List;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.data.domain.Sort;
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import org.springframework.stereotype.Service;
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import org.springframework.transaction.annotation.Transactional;
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/**
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* @author Kavindu Perera
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*/
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@Service
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@Transactional
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public class OrderEventService {
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private static final Logger log = LoggerFactory.getLogger(OrderEventService.class);
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private final OrderEventRepository orderEventRepository;
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private final OrderEventPublisher orderEventPublisher;
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private final ObjectMapper objectMapper;
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OrderEventService(
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OrderEventRepository orderEventRepository,
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ObjectMapper objectMapper,
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OrderEventPublisher orderEventPublisher) {
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this.orderEventRepository = orderEventRepository;
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this.objectMapper = objectMapper;
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this.orderEventPublisher = orderEventPublisher;
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}
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void save(OrderCreatedEvent event) {
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OrderEventEntity orderEvent = new OrderEventEntity();
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orderEvent.setEventId(event.eventId());
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orderEvent.setEventType(OrderEventType.ORDER_CREATED);
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orderEvent.setOrderNumber(event.orderNumber());
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orderEvent.setCreatedAt(event.createdAt());
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orderEvent.setPayload(toJsonPayload(event));
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this.orderEventRepository.save(orderEvent);
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}
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public void publishOrderEvents() {
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Sort sort = Sort.by("createdAt").ascending();
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List<OrderEventEntity> events = orderEventRepository.findAll(sort);
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log.info("Found {} Order Events to publish", events.size());
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for (OrderEventEntity event : events) {
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this.publishEvent(event);
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orderEventRepository.delete(event);
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}
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}
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private void publishEvent(OrderEventEntity event) {
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OrderEventType eventType = event.getEventType();
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switch (eventType) {
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case ORDER_CREATED:
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OrderCreatedEvent orderCreatedEvent = fromJsonPayload(event.getPayload(), OrderCreatedEvent.class);
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orderEventPublisher.publish(orderCreatedEvent);
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break;
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default:
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log.warn("Unknown Event Type: {}", eventType);
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}
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}
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private String toJsonPayload(Object object) {
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try {
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return objectMapper.writeValueAsString(object);
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} catch (JsonProcessingException e) {
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throw new RuntimeException(e);
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}
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}
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private <T> T fromJsonPayload(String json, Class<T> type) {
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try {
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return objectMapper.readValue(json, type);
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} catch (JsonProcessingException e) {
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throw new RuntimeException(e);
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}
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}
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}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/domain/OrderService.java

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import com.codebykavindu.bookstore.orders.domain.models.CreateOrderRequest;
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import com.codebykavindu.bookstore.orders.domain.models.CreateOrderResponse;
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import com.codebykavindu.bookstore.orders.domain.models.OrderCreatedEvent;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.stereotype.Service;
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private final OrderRepository orderRepository;
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private final OrderValidator orderValidator;
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private final OrderEventService orderEventService;
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OrderService(OrderRepository orderRepository, OrderValidator orderValidator) {
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OrderService(OrderRepository orderRepository, OrderValidator orderValidator, OrderEventService orderEventService) {
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this.orderRepository = orderRepository;
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this.orderValidator = orderValidator;
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this.orderEventService = orderEventService;
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}
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public CreateOrderResponse createOrder(String userName, CreateOrderRequest request) {
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newOrder.setUserName(userName);
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OrderEntity savedOrder = this.orderRepository.save(newOrder);
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log.info("Created Order with orderNumber={}", savedOrder.getOrderNumber());
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OrderCreatedEvent orderCreatedEvent = OrderEventMapper.buildOrderCreatedEvent(savedOrder);
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orderEventService.save(orderCreatedEvent);
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return new CreateOrderResponse(savedOrder.getOrderNumber());
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}
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}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/domain/models/OrderCreatedEvent.java

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package com.codebykavindu.bookstore.orders.domain.models;
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import java.time.LocalDateTime;
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import java.util.Set;
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/**
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* @author Kavindu Perera
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*/
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public record OrderCreatedEvent(
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String eventId,
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String orderNumber,
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Set<OrderItem> items,
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Customer customer,
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Address deliveryAddress,
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LocalDateTime createdAt) {}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/domain/models/OrderEventType.java

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package com.codebykavindu.bookstore.orders.domain.models;
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/**
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* @author Kavindu Perera
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*/
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public enum OrderEventType {
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ORDER_CREATED,
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ORDER_DELIVERED,
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ORDER_CANCELLED,
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ORDER_PROCESSING_FAILED
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}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/jobs/OrderEventPublishingJob.java

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package com.codebykavindu.bookstore.orders.jobs;
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import com.codebykavindu.bookstore.orders.domain.OrderEventService;
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import java.time.Instant;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.scheduling.annotation.Scheduled;
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import org.springframework.stereotype.Component;
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/**
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* @author Kavindu Perera
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*/
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@Component
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class OrderEventPublishingJob {
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private static final Logger log = LoggerFactory.getLogger(OrderEventPublishingJob.class);
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private final OrderEventService orderEventService;
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OrderEventPublishingJob(OrderEventService orderEventService) {
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this.orderEventService = orderEventService;
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}
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@Scheduled(cron = "${orders.publish-order-events-job-cron}")
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public void publishOrderEvents() {
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log.info("Publishing Order Events at {}", Instant.now());
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orderEventService.publishOrderEvents();
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}
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}

‎order-service/src/main/java/com/codebykavindu/bookstore/orders/web/controllers/RabbitMQController.java

-30
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