apollo-portal/src/main/java/com/ctrip/framework/apollo/openapi/v1/controller/NamespaceBranchController.java/NamespaceBranchController/findBranch
class NamespaceBranchController:    @GetMapping(value = "/apps/{appId}/clusters/{clusterName}/namespaces/{namespaceName}/branches")
    public OpenNamespaceDTO findBranch(@PathVariable String appId,
                                       @PathVariable String env,
                                       @PathVariable String clusterName,
                                       @PathVariable String namespaceName) {
        NamespaceBO namespaceBO = namespaceBranchService.findBranch(appId, Env.valueOf(env.toUpperCase()), clusterName, namespaceName);
        if (namespaceBO == null) {
            return null;
        }
        return OpenApiBeanUtils.transformFromNamespaceBO(namespaceBO);
    }