Build a Spring Cloud Gateway

  • 7 minutes

In this module, we'll build a Spring Cloud Gateway and deploy it on Azure Spring Apps.

Gateways are used to route public HTTP traffic to microservices:

  • They handle the routing logic.
  • They secure the access to the microservices, which won't be publicly available.
  • They can also have Quality of Service (QoS) capabilities, like doing HTTP rate limiting.

Create a Spring Cloud Gateway

To create our gateway, we use https://start.spring.io with the command line:

curl https://start.spring.io/starter.tgz -d type=maven-project -d dependencies=cloud-gateway,cloud-eureka,cloud-config-client -d baseDir=todo-gateway -d bootVersion=3.1.5.RELEASE -d javaVersion=17 | tar -xzvf -

Note

We use the Cloud Gateway, Eureka Discovery Client, and the Config Client components.

Configure the application

In the src/main/resources/application.properties configuration file, add the following property:

spring.main.allow-bean-definition-overriding=true
spring.cloud.gateway.discovery.locator.enabled=true
  • The spring.main.allow-bean-definition-overriding=true part is to configure Spring Cloud Gateway to use the Spring Cloud Discovery Server bean configured in the Azure Spring Apps Client library.
  • The spring.cloud.gateway.discovery.locator.enabled=true part is to configure Spring Cloud Gateway to use the Spring Cloud Service Registry to discover the available microservices.

Create the application on Azure Spring Apps

As in the previous module, create a specific todo-gateway application in your Azure Spring Apps instance. As this application is a gateway, we add the --assign-endpoint flag so it's exposed publicly.

az spring app create --name todo-gateway --service "$SPRING_CLOUD_NAME" --resource-group "$RESOURCE_GROUP_NAME" --runtime-version Java_17 --assign-endpoint

Deploy the application

You can now build your todo-gateway project and send it to Azure Spring Apps:

cd todo-gateway
./mvnw clean package -DskipTests
az spring app deploy --name todo-gateway --service "$SPRING_CLOUD_NAME" --resource-group "$RESOURCE_GROUP_NAME" --artifact-path target/demo-0.0.1-SNAPSHOT.jar
cd ..

Test the project in the cloud

  1. Go to Apps in your Azure Spring Apps instance.

    1. Verify todo-gateway has a registration status that says 1/1. This information shows that it's correctly registered in the Spring Cloud Service Registry.
    2. Select todo-gateway to have more information on the microservice.

  2. Copy/paste the public URL that's provided. Keep this URL handy for subsequent sections.

    There's a Test Endpoint—like for microservices—but the gateway is directly exposed on the internet, so we'll use the public URL.

As the gateway is connected to the Spring Cloud Service Registry, it should automatically open routes to the available microservices, with URL paths in the form of /MICROSERVICE-ID/**: [The MICROSERVICE-ID must be in capital letters]

Test the todo-service microservice endpoint by doing: curl https://XXXXXXXX-todo-gateway.azuremicroservices.io/TODO-SERVICE/ (replacing XXXXXXXX with the name of your Azure Spring Apps instance).

As in the previous module, the result of this command should be the three items that were initially inserted in the MySQL database:

[{"id":"1","description":"First item","done":true},{"id":"2","description":"Second item","done":true},{"id":"3","description":"Third item","done":false}]