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Tutorial: Use dynamic configuration in a Java Spring app

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App Configuration has two libraries for Spring.

  • spring-cloud-azure-appconfiguration-config requires Spring Boot and takes a dependency on spring-cloud-context.
  • spring-cloud-azure-appconfiguration-config-web requires Spring Web along with Spring Boot, and also adds support for automatic checking of configuration refresh.

Both libraries support manual triggering to check for refreshed configuration values.

Refresh allows you to update your configuration values without having to restart your application, though it causes all beans in the @RefreshScope to be recreated. It checks for any changes to configured triggers, including metadata. By default, the minimum amount of time between checks for changes, refresh interval, is set to 30 seconds.

spring-cloud-azure-appconfiguration-config-web's automated refresh is triggered based on activity, specifically Spring Web's ServletRequestHandledEvent. If a ServletRequestHandledEvent isn't triggered, spring-cloud-azure-appconfiguration-config-web's automated refresh doesn't trigger a refresh even if the cache expiration time has expired.

Use manual refresh

To use manual refresh, start with a Spring Boot app that uses App Configuration, such as the app you create by following the Spring Boot quickstart for App Configuration.

App Configuration exposes AppConfigurationRefresh, which can be used to check if the cache is expired. If it's expired, a refresh is triggered.

  1. To use AppConfigurationRefresh, update HelloController.

    import com.azure.spring.cloud.config.AppConfigurationRefresh;

@RestController
public class HelloController {
    private final MessageProperties properties;

    @Autowired(required = false)
    private AppConfigurationRefresh refresh;

    public HelloController(MessageProperties properties) {
        this.properties = properties;
    }

    @GetMapping
    public String getMessage() throws InterruptedException, ExecutionException {
        if (refresh != null) {
            refresh.refreshConfigurations();
        }
        return "Message: " + properties.getMessage();
    }
}

    AppConfigurationRefresh's refreshConfigurations() returns a Mono that is true if a refresh has been triggered, and false if not. False means either the cache expiration time hasn't expired, there was no change, or another thread is currently checking for a refresh.

  2. Update bootstrap.properties to enable refresh:

    spring.cloud.azure.appconfiguration.stores[0].monitoring.enabled=true
spring.cloud.azure.appconfiguration.stores[0].monitoring.refresh-interval= 30s
spring.cloud.azure.appconfiguration.stores[0].monitoring.triggers[0].key=sentinel

  3. Open the Azure Portal and navigate to your App Configuration resource associated with your application. Select Configuration Explorer under Operations and create a new key-value pair by selecting + Create > Key-value to add the following parameters:

    Key Value
    sentinel 1

    Leave Label and Content Type empty for now.

  4. Select Apply.

  5. Build your Spring Boot application with Maven and run it.

    mvn clean package
mvn spring-boot:run

  6. Open a browser window, and go to the URL: http://localhost:8080. You see the message associated with your key.

    You can also use curl to test your application, for example:

    curl -X GET http://localhost:8080/

  7. To test dynamic configuration, open the Azure App Configuration portal associated with your application. Select Configuration Explorer, and update the value of your displayed key, for example:

    Key Value
    /application/config.message Hello - Updated

  8. Update the sentinel key you created earlier to a new value. This change triggers the application to refresh all configuration keys once the refresh interval has passed.

    Key Value
    sentinel 2

  9. Refresh the browser page twice to see the new message displayed. The first time triggers the refresh, the second loads the changes.

Note

The library only checks for changes on the after the refresh interval has passed. If the period hasn't passed then no change is displayed. Wait for the period to pass, then trigger the refresh check.

Use automated refresh

To use automated refresh, start with a Spring Boot app that uses App Configuration, such as the app you create by following the Spring Boot quickstart for App Configuration.

Then, open the pom.xml file in a text editor and add a <dependency> for spring-cloud-azure-appconfiguration-config-web using the following code.

Spring Boot

<dependency>
    <groupId>com.azure.spring</groupId>
    <artifactId>spring-cloud-azure-appconfiguration-config-web</artifactId>
    <version>5.8.0</version>
</dependency>

  1. Update bootstrap.properties to enable refresh

    spring.cloud.azure.appconfiguration.stores[0].monitoring.enabled=true
spring.cloud.azure.appconfiguration.stores[0].monitoring.refresh-interval= 30s
spring.cloud.azure.appconfiguration.stores[0].monitoring.triggers[0].key=sentinel

  2. Open the Azure Portal and navigate to your App Configuration resource associated with your application. Select Configuration Explorer under Operations and create a new key-value pair by selecting + Create > Key-value to add the following parameters:

    Key Value
    sentinel 1

    Leave Label and Content Type empty for now.

  3. Select Apply.

  4. Build your Spring Boot application with Maven and run it.

    mvn clean package
mvn spring-boot:run

  5. Open a browser window, and go to the URL: http://localhost:8080. You now see the message associated with your key.

    You can also use curl to test your application, for example:

    curl -X GET http://localhost:8080/

  6. To test dynamic configuration, open the Azure App Configuration portal associated with your application. Select Configuration Explorer, and update the value of your displayed key, for example:

    Key Value
    /application/config.message Hello - Updated

  7. Update the sentinel key you created earlier to a new value. This change triggers the application to refresh all configuration keys once the refresh interval has passed.

    Key Value
    sentinel 2

  8. Refresh the browser page twice to see the new message displayed. The first time triggers the refresh, the second loads the changes, as the first request returns using the original scope.

Note

The library only checks for changes on after the refresh interval has passed. If the refresh interval hasn't passed, then it doesn't check for changes. Wait for the interval to pass, then trigger the refresh check.

Next steps

In this tutorial, you enabled your Spring Boot app to dynamically refresh configuration settings from App Configuration. For further questions see the reference documentation, it has all of the details on how the Spring Cloud Azure App Configuration library works. To learn how to use an Azure managed identity to streamline the access to App Configuration, continue to the next tutorial.

Managed identity integration