Message Module

Publisher

First, You must create or have an output port in the application service layer. So, You create an adapter for implement these ports.

Example: a spec with AsyncAPI

flowchart LR
   subgraph application service
       output_port
   end
   subgraph messaging module
     secondary_adapter
   end
    output_port --> secondary_adapter

Part I.

• Models from Event Specification(e.g: Avro Models)
• Mappers

Part II.

• Implementing output ports(Publishers/Producers)
  • Secondary Adapter
• Implementing input ports(Listener/Consumers)
  • Primary Adapter

Dependencies

Message ModelMessage Core

Important add the avro plugin and generate the avro models with mvn -pl blank-message/blank-message-model clean install

<dependency>
    <groupId>com.lg5.spring.kafka</groupId>
    <artifactId>lg5-spring-kafka-model</artifactId>
</dependency>

<!-- Implements OUTPUT ports from application service layer -->
<dependencies>
  <dependency>
    <groupId>com.blanksystem</groupId>
    <artifactId>blank-application-service</artifactId>
  </dependency>
  <dependency>
    <groupId>com.blanksystem</groupId>
    <artifactId>blank-message-model</artifactId>
  </dependency>
  <!-- if you need to produce events-->
  <dependency>
    <groupId>com.lg5.spring.kafka</groupId>
    <artifactId>lg5-spring-kafka-producer</artifactId>
  </dependency>
  <!-- if you need to consume events-->
  <dependency>
    <groupId>com.lg5.spring.kafka</groupId>
    <artifactId>lg5-spring-kafka-consumer</artifactId>
  </dependency>
</dependencies>

Plugins to generate avro models

Only for blank-message-model submodule.
* First, Add avro-maven-plugin for mng the avro model to java objects. * Second, Disable the maven-checkstyle-pluginwith <skip>true</skip>.

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-checkstyle-plugin</artifactId>
            <configuration>
                <skip>true</skip>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.avro</groupId>
            <artifactId>avro-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

Project structure

Message model structureMessage core structure

Important add the avro plugin and generate the avro models with mvn -pl blank-message/blank-message-model clean install

 src/
 ├── main/
 │  ├── java/
 │  │  └── com.blanksystem.message/
 │  │       └── model/
 │  │          └── avro/
 │  │             └── BlankAvroModel.java(autogenerate)
 │  └── resources/
 │     ├── avro/
 │     │  └── blank.avsc
 │     └── spec/
 │        └── asyncapi.yaml

Also, you must add the Async Api definition into resourses/spec/asyncapi.yaml

main/
└── java/
    └── com.blanksystem.blank.service.message
        ├── listener/
        │  └── kafka/
        │     └── BlankKafkaListener.java
        ├── mapper/
        │  └── BlankMessagingDataMapper.java
        └── publisher/
           └── kafka/
               └── BlankEventKafkaPublisher.java

Read more about openapi guidelines

2'DO

• Support for asyncapi definition and a process to avro files automatically generation.