Tutorial: Use dynamic configuration in a Java Spring app

App Configuration has two libraries for Spring. azure-spring-cloud-appconfiguration-config requires Spring Boot and takes a dependency on spring-cloud-context. azure-spring-cloud-appconfiguration-config-web requires Spring Web along with Spring Boot. Both libraries support manual triggering to check for refreshed configuration values. azure-spring-cloud-appconfiguration-config-web also adds support for automatic checking of configuration refresh.

Refresh allows you to refresh your configuration values without having to restart your application, though it will cause all beans in the @RefreshScope to be recreated. The client library caches a hash ID of the currently loaded configurations to avoid too many calls to the configuration store. The refresh operation doesn't update the value until the cached value has expired, even when the value has changed in the configuration store. The default expiration time for each request is 30 seconds. It can be overridden if necessary.

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

Use manual refresh

App Configuration exposes AppConfigurationRefresh which can be used to check if the cache is expired and if it is expired trigger a refresh.

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

...

@Autowired
private AppConfigurationRefresh appConfigurationRefresh;

...

public void myConfigurationRefreshCheck() {
    Future<Boolean> triggeredRefresh = appConfigurationRefresh.refreshConfigurations();
}

AppConfigurationRefresh's refreshConfigurations() returns a Future 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.

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 azure-spring-cloud-appconfiguration-config-web using the following code.

Spring Boot

<dependency>
    <groupId>com.azure.spring</groupId>
    <artifactId>azure-spring-cloud-appconfiguration-config-web</artifactId>
    <version>2.0.0</version>
</dependency>

Note

If you need support for older dependencies see our previous library.

  1. Update bootstrap.properties to enable refresh

    spring.cloud.azure.appconfiguration.stores[0].monitoring.enabled=true
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 will 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 will trigger the application to refresh all configuration keys once the refresh interval has passed.

    Key Value
    Sentinel 2

  8. Refresh the browser page to see the new message displayed.

Next steps

In this tutorial, you enabled your Spring Boot app to dynamically refresh configuration settings from App Configuration. To learn how to use an Azure managed identity to streamline the access to App Configuration, continue to the next tutorial.

Managed identity integration