Microservices with Java Spring Boot

Github repo for this project:

https://github.com/linhtch90/microservices-java-demo-zoo-devto

Introduction

Microservice is the concept of decomposing a large monolith application into small, independent, distributed services. This could improve the flexibility, scalability and resiliency of the whole system.

The introduction of Spring Cloud framework makes it easier for developers to build and deploy microservices to private and public clouds. This framework has wrapped a wide varieties of popular cloud-management microservices frameworks under a well-organized framework.

In this blog post, I want to help you have an overview about Spring Cloud framework by building a simple microservices system with Spring Cloud step by step. This system includes the following components:

• Configuration server
• Service discovery with Eureka
• 2 demo microservices called Tiger and Panther
• Gateway server
• RabbitMQ for messaging between microservices

The relationships between those services are described as the following figure.

Let's begin building this system!

Configuration server

Go to start.spring.io and generate a new project with the following information:

• Group ID: com.microservices.zooconfsvr
• Artifact ID: microservice-zoo-config-server
• Name: microservice-zoo-config-server
• Description: zoo microservices config server
• JDK: I am using JDK 17 for this tutorial. I have not tested this project with older JDKs yet!
• Dependencies: Config Server (So other services can get their configuration information from this service)

Your pom.xml should look like this:

<dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-config-server</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

• In folder src/main/resources/, add a file called bootstrap.properties
• In folder src/main/resources/, add a folder called config/ and create 4 configuration files eureka-server.properties, gateway-server.properties, panther-service.properties, tiger-service.properties
• The content of those .properties files could be found in my Github repo I put the link on top of this blog post)

Add @EnableConfigServer annotation to the main entrance class MicroserviceZooConfigServerApplication.java.

Service discovery (with Eureka)

Go to start.spring.io and generate a new project with the following information:

• Group ID: com.microservices.zooeurekasvr
• Artifact ID: microservice-zoo-services-discovery
• Name: microservice-zoo-services-discovery
• Description: zoo microservices services discovery
• Dependencies: Eureka server, config client

Your pom.xml should look like this:

<properties>
        <java.version>17</java.version>
        <spring-cloud.version>2021.0.0</spring-cloud.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

• In folder src/main/resources/, add a file called bootstrap.properties
• The content of those .properties files could be found in my Github repo (I put the link on top of this blog post)

Add @EnableEurekaServer annotation to MicroserviceZooServicesDiscoveryApplication.java

Gateway server

Gateway server is the service that handles all request from client. Go to start.spring.io and generate a new project with the following information:

• Group ID: com.microservices.zoogateway
• Artifact ID: microservice-zoo-gateway
• Name: microservice-zoo-gateway
• Description: microservice gateway for the zoo demo
• Dependencies: Eureka client, config client, gateway

Your pom.xml should look like this:

<properties>
        <java.version>17</java.version>
        <spring-cloud.version>2021.0.0</spring-cloud.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

• In folder src/main/resources/, add a file called bootstrap.properties
• The content of those .properties files could be found in my Github repo (I put the link on top of this blog post)

Add @EnableEurekaServer annotation to MicroserviceZooGatewayApplication.java

Tiger service

Go to start.spring.io and generate a new project with the following information:

• Group ID: com.microservices.tigerservice
• Artifact ID: microservice-tiger
• Name: microservice-tiger
• Description: microservice tiger
• Dependencies: Eureka client, config client, web, client load balancer, open feign (also for load balancer), RabbitMQ

Your pom.xml should look like this:

<dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework.cloud/spring-cloud-starter-openfeign -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
            <version>3.1.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-amqp</artifactId>
    </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

• In folder src/main/resources/, add a file called bootstrap.properties
• The content of those .properties files could be found in my Github repo (I put the link on top of this blog post)

Add @EnableFeignClients annotation to MicroserviceTigerApplication.java

• Create com.microservices.tigerservice.service package and add 2 files ClientToPantherService.java for directly call Panther service and RabitMQSender.java for sending a string message to Panther via RabbitMQ.
• Create com.microservices.tigerservice.controller package and add TigerController.java, specifying controllers for calling Panther service.
• Create com.microservices.tigerservice.component package and add RabitMQSenderComponent.java for creating Beans related to messaging service.
• Please refer to my Github repo for the content of these files.

Panther service

Go to start.spring.io and generate a new project with the following information:

• Group ID: com.microservices.pantherservice
• Artifact ID: microservice-panther
• Name: microservice-panther
• Description: microservice panther
• Dependencies: Eureka client, config client, web, client load balancer, RabbitMQ

Your pom.xml should look like this:

<dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-amqp</artifactId>
    </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

• In folder src/main/resources/, add a file called bootstrap.properties
• The content of those .properties files could be found in my Github repo (I put the link on top of this blog post)

Create controller and other components for the services as follow.

• Create com.microservices.pantherservice.controller package and add TigerCallPanther.java for directly respond to calls from Tiger service in the form of a string.
• Create com.microservices.pantherservice.component package and add 2 files RabbitMQComponent.java and RabbitMQReceiver.java for settings related to listening and responding to messages sent from Tiger service. Right after receiving the message from Tiger service, Panther service print the message into the Log.
• Please refer to my Github repo for the content of these files.

RabbitMQ

Please refer to this tutorial for using RabbitMQ with Docker.

Running the whole system

Please follow this order:

• Start RabbitMQ with Docker (see above section)
• Start Configuration server
• Start Discovery service
• Start Tiger service
• Start Panther service
• Start Gateway server

Testing microservices with Postman

• Direct call from Tiger service to Panther service: Open Postman and send a request to

http://localhost:8074/tiger-service/tiger/callpantherservice

The result should look like the following figure.

• Send message from Tiger service to Panther service: Open Postman and send a request to

http://localhost:8074/tiger-service/tiger/sendmessagetopanther

There is not any response in Postman. It is okay. Please go to the terminal screen where you are running Panther service. You will see a log message saying:

Received message is: Message from Tiger to Panther via RabbitMQ

And that is all everybody!

If you feel this project is useful for you, please give my project a Github star ⭐ as an encouragement!

Thank you so much!