1.说明

本文详细介绍配置中心客户端使用方法，
即Config Client到Config Server读取配置，
这里以创建Config Client服务为例，
基于已经创建好的Config Server模块，
请参考SpringCloud创建Config模块,
到配置中心读取配置。

2.创建工程，添加依赖

在父工程下面创建一个Maven模块config-client，
在pom.xml中增加config client的依赖：

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-config</artifactId>
    </dependency>
    
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
</dependencies>

其中spring-boot-starter-web是spring boot应用，
可以对外提供Rest服务，
下面会通过Rest接口查询客户端读取到的配置。

3.新增配置文件

新增配置文件bootstrap.yml:

server:
  port: 8001

spring:
  application:
    name: config-client
  cloud:
    config:
      label: master
      name: config-client-demo
      profile: test
      uri: http://localhost:9009

上面的spring.cloud.config配置,
指定了配置中心http://localhost:9009，
拉取master分支下的config-client-demo.yml中的test配置。

4.git仓库增加配置

由于http://localhost:9009配置中心，
指定了spring-cloud-config仓库的地址：

https://gitee.com/bugzeroman/spring-cloud-config.git

需要把config-client-demo.yml上传到仓库，
这样客户端才能通过配置中心拉取到配置文件。
config-client-demo.yml内容：

spring:
  profiles:
    active:
    - test
    
---
# 开发环境
spring:
  profiles: dev
  application:
    name: config-server-dev

config:
  info: config info dev

---
# 测试环境
spring:
  profiles: test
  application:
    name: config-server-test
config:
  info: config info test

5.新增查询接口

ConfigClientController.java对外提供config.info参数的查询，
config.info是从配置中心读取的。

package com.yuwen.spring.config.client.controller;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ConfigClientController {

    @Value("${config.info}")
    private String configInfo;

    @GetMapping("/configInfo")
    public String getConfigInfo() {
        return configInfo;
    }
}

6.新增启动类

主启动类ConfigClientApplication.java，
只要加上SpringBootApplication注解：

package com.yuwen.spring.config.client;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ConfigClientApplication {
    public static void main(String[] args) {
        SpringApplication.run(ConfigClientApplication.class, args);
    }
}

7.启动服务

Config Client服务启动日志如下，
注意要先启动Config Server服务：

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.1.RELEASE)

2020-09-11 15:59:00.454  INFO 19236 --- [           main] c.c.c.ConfigServicePropertySourceLocator : Fetching config from server at : http://localhost:9009
2020-09-11 15:59:01.868  INFO 19236 --- [           main] c.c.c.ConfigServicePropertySourceLocator : Located environment: name=config-client-demo, profiles=[dev], label=master, version=befaf0fdb3897ac7b7de2a8df3192decb0192cb7, state=null
2020-09-11 15:59:01.869  INFO 19236 --- [           main] b.c.PropertySourceBootstrapConfiguration : Located property source: [BootstrapPropertySource {name='bootstrapProperties-configClient'}, BootstrapPropertySource {name='bootstrapProperties-https://gitee.com/bugzeroman/spring-cloud-config.git/config-client-demo.yml (document #1)'}, BootstrapPropertySource {name='bootstrapProperties-https://gitee.com/bugzeroman/spring-cloud-config.git/application.yml (document #1)'}, BootstrapPropertySource {name='bootstrapProperties-https://gitee.com/bugzeroman/spring-cloud-config.git/config-client-demo.yml (document #0)'}, BootstrapPropertySource {name='bootstrapProperties-https://gitee.com/bugzeroman/spring-cloud-config.git/application.yml (document #0)'}]
2020-09-11 15:59:01.874  INFO 19236 --- [           main] c.y.s.c.client.ConfigClientApplication   : No active profile set, falling back to default profiles: default
2020-09-11 15:59:02.239  INFO 19236 --- [           main] o.s.cloud.context.scope.GenericScope     : BeanFactory id=7db33b17-4254-3471-a240-faf5a3bf9fa9
2020-09-11 15:59:02.660  INFO 19236 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8001 (http)
2020-09-11 15:59:02.668  INFO 19236 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-09-11 15:59:02.668  INFO 19236 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.36]
2020-09-11 15:59:02.750  INFO 19236 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-09-11 15:59:02.750  INFO 19236 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 865 ms
2020-09-11 15:59:02.847  INFO 19236 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-09-11 15:59:03.248  INFO 19236 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8001 (http) with context path ''
2020-09-11 15:59:03.531  INFO 19236 --- [           main] c.y.s.c.client.ConfigClientApplication   : Started ConfigClientApplication in 4.184 seconds (JVM running for 4.49)
2020-09-11 15:59:30.056  INFO 19236 --- [nio-8001-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2020-09-11 15:59:30.056  INFO 19236 --- [nio-8001-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2020-09-11 15:59:30.060  INFO 19236 --- [nio-8001-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 4 ms

8.测试服务

访问Config Client提供的Rest服务：
http://localhost:8001/configInfo

修改bootstrap.yml中spring.cloud.config.profile为dev，
然后重新启动，再次访问上面的接口：

可以看到两次分别拉取到了config-client-demo.yml中对应的配置。

9.参考文章

Spring Cloud Config Server 官方手册
Spring Cloud Config 中文手册