apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/controller/PrefixPathController.java/PrefixPathController/getPrefixPath
class PrefixPathController:  @GetMapping("/prefix-path")
  public String getPrefixPath() {
    if (Strings.isNullOrEmpty(prefixPath)) {
      return servletContext.getContextPath();
    }
    return prefixPath;
  }