Spring Cloud Config Server提供了微服务获取配置的功能，这些配置文件（application.yml或者application.properties）通常维护在git或者数据库中，而且支持通过RefreshScope动态刷新，使用起来还是比较灵活的。但是当微服务越来越多时，会遇到下面几个问题：

1. 配置文件的敏感数如数据库地址和账号信息，据呈现在每个配置文件中，替换起来需要一个个配置文件进行修改。
2. 各个微服务配置文件存在很多冗余配置（如Eureka，Feign），一旦这些部分调整，需要针对每个微服务进行调整，运维压力大增。

为了解决上述问题，我们可以从configServer服务着手进行改造，示意如下：

不同的服务ABC，不管是在配置中心仓库端配置了多少个文件，从ConfigServer返回的，一定是服务最终应用的配置。获取配置的方式，通常是调用ConfigServer的一个地址，如：

http://localhost:8021/common_rent/dev/aliyun_dev

common_rent是application name，dev是profile，aliyun_dev是label（git的分支）。这个地址的处理接口，是ConfigServer的EnvironmentController，所以通过拦截这个接口，将敏感信息或者公共配置抽取到configServer的application.yml, 返回前进行替换或者拼接，即可实现上述目的。

代码示例：

1. 拦截器实现

   @Component
   @Aspect
   public class ResourceLoaderInterceptor {
   
   private static Log logger = LogFactory.getLog(ResourceLoaderInterceptor.class);
   @Resource
   ExternalProperties externalProperties;
   
   @Around("execution(* org.springframework.cloud.config.server..*Controller.*(..)) ")
   public Object commonPropertiesResolve(ProceedingJoinPoint joinPoint) throws Throwable {
       Object returnObj = null;
       Object[] args = joinPoint.getArgs();
       StopWatch stopWatch = new StopWatch();
       try {
           stopWatch.start();
           returnObj = joinPoint.proceed(args);
           if (Environment.class.isInstance(returnObj)) {
               Environment environment = (Environment) returnObj;
               if (environment.getPropertySources() != null && environment.getPropertySources().size() > 0) {
                   for (PropertySource propertySource : environment.getPropertySources()) {
                       placeHolderResolve((Map) propertySource.getSource());
                   }
               }
           }
       } catch (Throwable throwable) {
           logger.error(ExceptionUtils.getStackTrace(throwable));
       } finally {
           stopWatch.stop();
           System.out.println(stopWatch.getTotalTimeMillis());
       }
       return returnObj;
   
   }
   
   private void placeHolderResolve(Map source) {
       Map placeHolders = collectConfigSet();
       for (String key : source.keySet()) {
           Object value = source.get(key);
           Object valueAfterReplace = null;
           if (value != null) {
               if (String.class.isInstance(value) && ((String) value).contains("${ext.")) {
                   String varExp = (String) value;
                   for (String variable : placeHolders.keySet()) {
                       String vk = "${" + variable + "}";
                       if (varExp.contains(vk)) {
                           Object replaceValue = placeHolders.get(variable);
                           if (replaceValue != null) {
                               if (varExp.equalsIgnoreCase(vk)) {
                                   valueAfterReplace = replaceValue;
                                   break;
                               } else {
                                   varExp = StringUtils.replace(varExp, vk, "" + replaceValue);
                                   if (!varExp.contains("${")) {
                                       break;
                                   }
                               }
                           } else {
                               logger.error("Property " + vk + " is not properly configured!");
                           }
                       }
                   }
                   if (valueAfterReplace != null) {
                       source.put(key, valueAfterReplace);
                   } else if (varExp.contains("${")) {
                       logger.error("Property " + varExp + " is not properly configured!");
                   } else {
                       source.put(key, varExp);
                   }
               }
           }
       }
   }
   
   private Map collectConfigSet() {
       Map placeHolders = new HashMap<>();
       Field[] fields = ExternalProperties.class.getDeclaredFields();
       for (int i = 0; i < fields.length; i++) {
           try {
               Field propertiesField = fields[i];
               ResourcePrefix resourcePrefix = propertiesField.getAnnotation(ResourcePrefix.class);
               String prefix = resourcePrefix.value();
               ExtDataSource extDataSource = (ExtDataSource) BeanUtils.getPropertyDescriptor(ExternalProperties.class, propertiesField.getName()).getReadMethod().invoke(externalProperties);
               if (extDataSource != null) {
                   Field[] fields2 = ExtDataSource.class.getDeclaredFields();
                   for (Field datasourceField : fields2) {
                       try {
                           ResourcePrefix annotation = datasourceField.getAnnotation(ResourcePrefix.class);
                           String suffix = annotation.value();
                           Object sourceFieldValue = BeanUtils.getPropertyDescriptor(ExtDataSource.class, datasourceField.getName()).getReadMethod().invoke(extDataSource);
                           if (sourceFieldValue != null) {
                               placeHolders.put(prefix + "." + suffix, sourceFieldValue);
                           }
                       } catch (Exception e) {
                           logger.error(ExceptionUtils.getStackTrace(e));
                       }
                   }
               }
           } catch (Exception e) {
               logger.error(ExceptionUtils.getStackTrace(e));
           }
       }
       return placeHolders;
   }
   }

2. ExternalProperites实现

@ConfigurationProperties(prefix = "external", ignoreUnknownFields = true)
public class ExternalProperties implements Serializable {

    @ResourcePrefix(value = "ext.spring.datasource")
    private ExtDataSource datasource;
    @ResourcePrefix(value = "ext.spring.data.mongodb")
    private ExtDataSource mongodb;
    @ResourcePrefix(value = "ext.spring.redis")
    private ExtDataSource redis;
    @ResourcePrefix(value = "ext.spring.rabbitmq")
    private ExtDataSource rabbitmq;

    public ExtDataSource getDatasource() {
        return datasource;
    }

    public void setDatasource(ExtDataSource datasource) {
        this.datasource = datasource;
    }

    public ExtDataSource getRabbitmq() {
        return rabbitmq;
    }

    public void setRabbitmq(ExtDataSource rabbitmq) {
        this.rabbitmq = rabbitmq;
    }

    public ExtDataSource getMongodb() {
        return mongodb;
    }

    public void setMongodb(ExtDataSource mongodb) {
        this.mongodb = mongodb;
    }

    public ExtDataSource getRedis() {
        return redis;
    }

    public void setRedis(ExtDataSource redis) {
        this.redis = redis;
    }
}

3. ExtDataSource实现

   public class ExtDataSource {
   @ResourcePrefix(value = "host")
   private String host;
   @ResourcePrefix(value = "port")
   private Integer port;
   @ResourcePrefix(value = "url")
   private String url;
   @ResourcePrefix(value = "uri")
   private String uri;
   @ResourcePrefix(value = "username")
   private String userName;
   @ResourcePrefix(value = "password")
   private String password;
   
   public String getUrl() {
       return url;
   }
   
   public void setUrl(String url) {
       this.url = url;
   }
   
   public String getHost() {
       return host;
   }
   
   public void setHost(String host) {
       this.host = host;
   }
   
   public Integer getPort() {
       return port;
   }
   
   public void setPort(Integer port) {
       this.port = port;
   }
   
   public String getUri() {
       return uri;
   }
   
   public void setUri(String uri) {
       this.uri = uri;
   }
   
   public String getUserName() {
       return userName;
   }
   
   public void setUserName(String userName) {
       this.userName = userName;
   }
   
   public String getPassword() {
       return password;
   }
   
   public void setPassword(String password) {
       this.password = password;
   }
   }

4. ResourcePrefix实现

   @Target({ElementType.FIELD, ElementType.TYPE})
   @Retention(RetentionPolicy.RUNTIME)
   public @interface ResourcePrefix {
   String value();
   }

然后在configServer的application.yml中增加相关信息，如

external:
  datasource:
    host: 122.122.111.111
    port: 3307
    userName: usr
    password: pwd
  mongodb:
    host: 122.122.111.111
    port: 20467
    uri: 122.122.111.111:20467,122.122.111.112:20467,122.122.111.112:20467
    userName: usr
    password:  pwd
  redis:
    uri: 122.122.111.113:6379,122.122.112.113:6379,122.122.111.113:6379
    password: redispassword
  rabbitmq:
    host: 122.122.111.113
    port: 20467
    userName: usr
    password: pwd

将ServiceA的配置文件serviceA_dev.yml中的数据库相关信息替换成变量，以mysql为例
spring.datasource.uri: url: jdbc:mysql://#{ext.spring.datasource.host}:#{ext.spring.datasource.port}/dbName?useUnicode=true&characterEncoding=utf8,
serviceB和serviceC配置文件做同样处理，即可实现一次性替换。

后续如果需要增加公共配置，可以直接在ConfigServer的配置中间中增加，调整下拦截器的实现逻辑即可。