apollo-core/src/main/java/com/ctrip/framework/apollo/core/internals/LegacyMetaServerProvider.java/LegacyMetaServerProvider/getMetaServerAddress
class LegacyMetaServerProvider:  @Override
  public String getMetaServerAddress(Env targetEnv) {
    String metaServerAddress = domains.get(targetEnv);
    return metaServerAddress == null ? null : metaServerAddress.trim();
  }