apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/NamespaceBranchService.java/NamespaceBranchService/findBranch
class NamespaceBranchService:  public NamespaceBO findBranch(String appId, Env env, String clusterName, String namespaceName) {
    NamespaceDTO namespaceDTO = findBranchBaseInfo(appId, env, clusterName, namespaceName);
    if (namespaceDTO == null) {
      return null;
    }
    return namespaceService.loadNamespaceBO(appId, env, namespaceDTO.getClusterName(), namespaceName);
  }