How to Implement Dynamic Distributed Configuration with Nacos in Spring Boot

Welcome to part 4 of the Nacos series, focusing on distributed configuration practice.

Steps:

Create a Spring Boot service using local configuration.

Create configuration in Nacos.

Integrate Nacos configuration into the service.

Enable dynamic refresh of configuration.

1. Create Service

pom.xml:

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.2.5.RELEASE</version>
</parent>
<groupId>com.example</groupId>
<artifactId>configdemo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>configdemo</name>
<description>Demo project for Spring Boot</description>
<properties>
  <java.version>11</java.version>
</properties>
<dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>
  <!-- add dependency nacos-config -->
  <dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
  </dependency>
</dependencies>
<dependencyManagement>
  <dependencies>
    <!-- spring cloud dependency management -->
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-dependencies</artifactId>
      <version>Hoxton.SR3</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
    <!-- spring cloud alibaba dependency management -->
    <dependency>
      <groupId>com.alibaba.cloud</groupId>
      <artifactId>spring-cloud-alibaba-dependencies</artifactId>
      <version>2.2.1.RELEASE</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

Add configuration (application.yaml):

test:
  name: local-config

Add a test controller to output the configuration value:

@RestController
public class TestController {
    @Value("${test.name}")
    private String test_name;

    @GetMapping("/test")
    public String testpriority() {
        return test_name;
    }
}

Start the application and visit http://localhost:8080/test. The response shows the local configuration value.

2. Create Configuration in Nacos

Open the Nacos console configuration list page:

Click “Create Configuration”, set Data ID to configdemo.yaml, choose YAML format, and enter:

test:
  name: nacos-config

Publish the configuration. The new entry appears in the list:

3. Integrate Nacos Config into Service

Rename application.yaml to bootstrap.yaml because bootstrap.yaml has the highest priority.

Add Nacos settings to bootstrap.yaml:

spring:
  application:
    name: configdemo
  cloud:
    nacos:
      config:
        server-addr: localhost:8848
        file-extension: yaml

Now the local test.name entry is removed. Restart the service; the startup log shows that the configuration is loaded from Nacos.

Access http://localhost:8080/test again; the response is now nacos-config, confirming that the service reads the configuration from Nacos.

Explanation: During startup Spring reads bootstrap.yaml, uses spring.application.name and spring.cloud.nacos.config.file-extension to construct the Data ID, which allows it to fetch the corresponding configuration from Nacos.

4. Dynamic Refresh

To enable automatic refresh after modifying Nacos configuration, add the @RefreshScope annotation to the controller.

@RefreshScope
@RestController
public class TestController {
    @Value("${test.name}")
    private String test_name;

    @GetMapping("/test")
    public String testpriority() {
        return test_name;
    }
}

Restart the service, then modify the configuration in the Nacos console (append -new) and publish.

After confirming the change, the new value appears when the endpoint is refreshed, without restarting the service, demonstrating successful dynamic configuration refresh.