apollo-core/src/main/java/com/ctrip/framework/foundation/internals/provider/DefaultServerProvider.java/DefaultServerProvider/getProperty
class DefaultServerProvider:  @Override
  public String getProperty(String name, String defaultValue) {
    if ("env".equalsIgnoreCase(name)) {
      String val = getEnvType();
      return val == null ? defaultValue : val;
    }
    if ("dc".equalsIgnoreCase(name)) {
      String val = getDataCenter();
      return val == null ? defaultValue : val;
    }
    String val = m_serverProperties.getProperty(name, defaultValue);
    return val == null ? defaultValue : val.trim();
  }