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Centralized configuration using Spring Cloud Config


In this blog we will be focusing on centralized configuration using Spring Cloud Config project.
For single standalone application we can keep all required configuration bundle with application itself.  However, when we have more than one application, say in a microservice architecture, a better alternative would be to manage the configurations centrally.
With the Config Server we have a central place to manage external properties for applications with support for different environments. Configuration files in several formats like YAML or properties are added to a Git repository.

Features

Spring Cloud Config Server features:
  • HTTP, resource-based API for external configuration (name-value pairs, or equivalent YAML content)
  • Encrypt and decrypt property values (symmetric or asymmetric)
  • Embeddable easily in a Spring Boot application using @EnableConfigServer
Config Client features (for Spring applications):
  • Bind to the Config Server and initialize Spring Environment with remote property sources
  • Encrypt and decrypt property values (symmetric or asymmetric)

Use case :
  • We will keep application configuration file on GIT https://github.com/ketan-gote/config
  • Config-Server : This application serves all the application properties on REST.
  • Config-Client : This application talks to Config-Server and get the application properties during bootstrap.
Note : Here we will not focus securing properties files or REST calls, Please check Spring Cloud Config for more on that.

Centralized configuration on GIT:
URL: https://github.com/ketan-gote/config
It contains configclient.yml














Config Server
This application connects to git and serves configuration to required application.
Dependencies:

application.yml (config file) : This will have from cloud config url, in our case its git.


Above URI is public, if its private you will required to provide username/password as below.
For development purpose you will required to keep config files locally, which can be done as below (here we have used properties file instead of yml)


Below is code for Spring-Boot application:



Start the application and enter http://localhost:8081/configclient/default in browser.Config file on git is now available on REST call.



Config-Client
This is also spring boot application, which communicates to config-server for its required configuration.
Here we have created one rest endpoint which will display properties.
Dependencies:


bootstrap.yml – All configuration is required before application boots up, so instead of application.yml we will have bootstrap.yml file. This has application name (needs to exactly same as defined on git) and config-server URL.















Below is code for spring-boot application with one rest endpoint.




Now start the application and enter in browser




Cheers - Happy Learning 
Ketan Gote




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