Java client for Kubernetes & OpenShift 3
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Kubernetes & OpenShift 3 Java Client Join the chat at

This client provides access to the full Kubernetes & OpenShift 3 REST APIs via a fluent DSL.

CircleCI Dependency Status

  • kubernetes-client: Maven Central Javadocs
  • kubernetes-model: Maven Central Javadocs
  • openshift-client: Maven Central Javadocs


Creating a client

The easiest way to create a client is:

KubernetesClient client = new DefaultKubernetesClient();

DefaultOpenShiftClient implements both the KubernetesClient & OpenShiftClient interface so if you need the OpenShift extensions, such as Builds, etc then simply do:

OpenShiftClient osClient = new DefaultOpenShiftClient();

Configuring the client

This will use settings from different sources in the following order of priority:

  • System properties
  • Environment variables
  • Kube config file
  • Service account token & mounted CA certificate

System properties are preferred over environment variables. The following system properties & environment variables can be used for configuration:

  • kubernetes.master / KUBERNETES_MASTER
  • kubernetes.api.version / KUBERNETES_API_VERSION
  • kubernetes.oapi.version / KUBERNETES_OAPI_VERSION
  • kubernetes.disable.hostname.verification / KUBERNETES_DISABLE_HOSTNAME_VERIFICATION
  • kubernetes.certs.client.file / KUBERNETES_CERTS_CLIENT_FILE
  • kubernetes.certs.client.key.file / KUBERNETES_CERTS_CLIENT_KEY_FILE
  • kubernetes.certs.client.key.algo / KUBERNETES_CERTS_CLIENT_KEY_ALGO
  • kubernetes.certs.client.key.passphrase / KUBERNETES_CERTS_CLIENT_KEY_PASSPHRASE
  • kubernetes.auth.basic.username / KUBERNETES_AUTH_BASIC_USERNAME
  • kubernetes.auth.basic.password / KUBERNETES_AUTH_BASIC_PASSWORD
  • kubernetes.auth.tryKubeConfig / KUBERNETES_AUTH_TRYKUBECONFIG
  • kubernetes.auth.tryServiceAccount / KUBERNETES_AUTH_TRYSERVICEACCOUNT
  • kubernetes.auth.token / KUBERNETES_AUTH_TOKEN
  • kubernetes.user.agent / KUBERNETES_USER_AGENT
  • kubernetes.tls.versions / KUBERNETES_TLS_VERSIONS
  • kubernetes.truststore.file / KUBERNETES_TRUSTSTORE_FILE
  • kubernetes.truststore.passphrase / KUBERNETES_TRUSTSTORE_PASSPHRASE
  • kubernetes.keystore.file / KUBERNETES_KEYSTORE_FILE
  • kubernetes.keystore.passphrase / KUBERNETES_KEYSTORE_PASSPHRASE

Alternatively you can use the ConfigBuilder to create a config object for the Kubernetes client:

Config config = new ConfigBuilder().withMasterUrl("").build();
KubernetesClient client = new DefaultKubernetesClient(config);

Using the DSL is the same for all resources.

List resources:

NamespaceList myNs = client.namespaces().list();

ServiceList myServices =;

ServiceList myNsServices ="default").list();

Get a resource:

Namespace myns = client.namespaces().withName("myns").get();

Service myservice ="default").withName("myservice").get();


Namespace myns = client.namespaces().withName("myns").delete();

Service myservice ="default").withName("myservice").delete();

Editing resources uses the inline builders from the Kubernetes Model:

Namespace myns = client.namespaces().withName("myns").edit()
                     .addToLabels("a", "label")

Service myservice ="default").withName("myservice").edit()
                       .addToLabels("another", "label")

In the same spirit you can inline builders to create:

Namespace myns = client.namespaces().createNew()
                     .addToLabels("a", "label")

Service myservice ="default").createNew()
                       .addToLabels("another", "label")

You can also set the apiVersion of the resource like in the case of SecurityContextConstraints :

SecurityContextConstraints scc = new SecurityContextConstraintsBuilder()

Following events

Use io.fabric8.kubernetes.api.model.Event as T for Watcher: Watcher<Event>() {

  public void eventReceived(Action action, Event resource) {
    System.out.println("event " + + " " + resource.toString());

  public void onClose(KubernetesClientException cause) {
    System.out.println("Watcher close due to " + cause);


Working with extensions

The kubernetes API defines a bunch of extensions like daemonSets, jobs, ingresses and so forth which are all usable in the extensions() DSL:

e.g. to list the jobs...

jobs = client.batch().jobs().list();

Loading resources from external sources

There are cases where you want to read a resource from an external source, rather than defining it using the clients DSL. For those cases the client allows you to load the resource from:

  • A file (Supports both and java.lang.String)
  • A url
  • An input stream

Once the resource is loaded, you can treat it as you would, had you created it yourself.

For example lets read a pod, from a yml file and work with it:

Pod refreshed = client.load('/path/to/a/pod.yml').fromServer().get();
Boolean deleted = client.load('/workspace/pod.yml').delete();
LogWatch handle = client.load('/workspace/pod.yml').watchLog(System.out);

Passing a reference of a resource to the client

In the same spirit you can use an object created externally (either a a reference or using its string representation.

For example:

Pod pod = someThirdPartyCodeThatCreatesAPod();
Boolean deleted = client.resource(pod).delete();

Adapting the client

The client supports plug-able adapters. An example adapter is the OpenShift Adapter which allows adapting an existing KubernetesClient instance to an OpenShiftClient one.

For example:

KubernetesClient client = new DefaultKubernetesClient();

OpenShiftClient oClient = client.adapt(OpenShiftClient.class);

The client also support the isAdaptable() method which checks if the adaptation is possible and returns true if it does.

KubernetesClient client = new DefaultKubernetesClient();
if (client.isAdaptable(OpenShiftClient.class)) {
    OpenShiftClient oClient = client.adapt(OpenShiftClient.class);
} else {
    throw new Exception("Adapting to OpenShiftClient not support. Check if adapter is present, and that env provides /oapi root path.");

Adapting and close

Note that when using adapt() both the adaptee and the target will share the same resources (underlying http client, thread pools etc). This means that close() is not required to be used on every single instance created via adapt. Calling close() on any of the adapt() managed instances or the original instance, will properly clean up all the resources and thus none of the instances will be usable any longer.

Mocking Kubernetes

Along with the client this project also provide a kubernetes mock server that you can use for testing purposes. The mock server is based on but is empowered by the DSL and features provided by

The Mock Web Server has two modes of operation:

  • Expectations mode
  • CRUD mode

Expectations mode

It's the typical mode where you first set which are the expected http requests and which should be the responses for each request. More details on usage can be found at:

This mode has been extensively used for testing the client itself. Make sure you check kubernetes-test.

To add a Kubernetes server to your test:

 public KubernetesServer server = new KubernetesServer();

CRUD mode

Defining every single request and response can become tiresome. Given that in most cases the mock webserver is used to perform simple crud based operations, a crud mode has been added. When using the crud mode, the mock web server will store, read, update and delete kubernetes resources using an in memory map and will appear as a real api server.

To add a Kubernetes Server in crud mode to your test:

 public KubernetesServer server = new KubernetesServer(true, true);

Then you can use the server like:

public void testInCrudMode() {
KubernetesClient client = server.getClient();
  client.pods().inNamespace("ns1").create(new PodBuilder().withNewMetadata().withName("pod1").endMetadata().build());

  podList = client.pods().inNamespace("ns1").list();
  assertEquals(1, podList.getItems().size());


  podList = client.pods().inNamespace("ns1").list();
  assertEquals(0, podList.getItems().size());

Compatibility Matrix

Kubernetes 1.4.9 Kubernetes 1.6.0 Kubernetes 1.7.0 Kubernetes 1.9.0
kubernetes-client 1.3.92 + + - -
kubernetes-client 3.0.3 - - -
kubernetes-client 3.0.10 -
kubernetes-client 3.0.11 -
kubernetes-client 3.1.12 -
kubernetes-client 3.2.0 -
kubernetes-client 4.0.0 -
OpenShift 3.6.0 OpenShift 3.7.0 OpenShift 3.9.0
kubernetes-client 1.3.92 + - -
kubernetes-client 3.0.3 - -
kubernetes-client 3.0.10
kubernetes-client 3.0.11
kubernetes-client 3.1.12
kubernetes-client 3.2.0
kubernetes-client 4.0.0

Major Changes in Kubernetes Client 4.0.0

All the resource objects used here will be according to OpenShift 3.9.0 and Kubernetes 1.9.0. All the resource objects will give all the fields according to OpenShift 3.9.0 and Kubernetes 1.9.0

  • SecurityContextConstraints has been moved to OpenShift client from Kubernetes Client
  • Job dsl is in both batch and extensions(Extensions is deprecated)
  • DaemonSet dsl is in both apps and extensions(Extensions is deprecated)
  • Deployment dsl is in both apps and extensions(Extensions is deprecated)
  • ReplicaSet dsl is in both apps and extensions(Extensions is deprecated)
  • NetworkPolicy dsl is in both network and extensiosn(Extensions is deprecated)
  • Storage Class moved from client base DSL to storage DSL
  • PodSecurityPolicies moved from client base DSL and extensions to only extensions
  • ThirdPartyResource has been removed.

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