Java library for OpenStack Storage, aka Swift

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JOSS is a Java client for the OpenStack Storage component REST interface. In order to use it you must have an account with an OpenStack Storage provider, such as the CloudVPS Object Store.

In order to use JOSS in your project, simply add the following dependency:


You can also download the artifact on Maven Search

Getting Started

Your Object Store provider will have provided you with the following information in order to authenticate yourself:

  • tenantId (or tenantName)
  • username
  • password
  • authentication URL

We start by opening up a stateful client and authenticating ourselves:

    AccountConfig config = new AccountConfig()
            .setUsername( username)
    Account account = new AccountFactory(config).createAccount();

Note that you do not have to pass both tenant ID and tenant name; passing either tenant ID or tenant name is sufficient.

On failure, the client will throw an exception. On success, the account can now be used to execute actions on the Object Store. The account takes care of adding the token to the calls, so you don't have to worry about that. You should be aware, however, that tokens expire after 24 hours. The client will get a new token when it encounters a 401 and retry the original command just once.

Next, we want to create a public container, where we can store our images:

    Container container = account.getContainer("images");

A container is private by default, so you will have to explicitly set it to public to be able to access it through its public URL.

To check whether the creation succeeded, list the containers.

    Collection<Container> containers = account.list();
    for (Container currentContainer : containers) {

Now it is time to upload a file to the Object Store. In this example, we take an image located in the root directory of the file system.

    StoredObject object = container.getObject("dog.png");
    object.uploadObject(new File("/dog.png"));
    System.out.println("Public URL: "+object.getPublicURL());

If you fire up your browser, you can navigate to the public URL to see your resource for real. This is only possible because the container has been set to public. If it was private, you would not be able to do this.

You can also check whether the upload succeeded by listing the objects in a container or by fetching the object information.

    System.out.println("Last modified:  "+object.getLastModified());
    System.out.println("ETag:           "+object.getEtag());
    System.out.println("Content type:   "+object.getContentType());
    System.out.println("Content length: "+object.getContentLength());

    Collection<StoredObject> objects = container.list();
    for (StoredObject currentObject : objects) {

Alternatively, besides File, you could also use a byte[] or an InputStream to upload a file.

It is time to download what you just uploaded. Here we go.

    object.downloadObject(new File("/dog2.png"));

Open the file "/dog2.png" on the file system to verify that the operation worked. Again, also byte[] and InputStream are at your disposal. On using InputStream be aware that you are responsible for closing the stream by calling close() on the wrapper.

Now, if you want the object to be retrievable through another URL, you will have to move the object. This is accomplished by executing first a copy, then a delete action.

    StoredObject newObject = container.getObject("new-dog.png");
    object.copyObject(container, newObject);
    System.out.println("Public URL: "+object.getPublicURL()); // no longer retrievable
    System.out.println("Public URL: "+newObject.getPublicURL()); // the new URL

You can once more use the browser to access both resources. You will see that the first URL gives you a 404, while the second one now gives you the original resource.

It is possible to add metadata to both containers and objects.

    Map<String, Object> metadata = new TreeMap<String, Object>();
    metadata.put("title", "Some Title");
    metadata.put("department", "Some Department");

Likewise, this information can be retrieved, as seen above.

    Map<String, Object> returnedMetadata = container.getMetadata();
    for (String name : returnedMetadata.keySet()) {
        System.out.println("META / "+name+": "+returnedMetadata.get(name));

There are many situations in which it is not necessary, not possible, or even plain clumsy, to be connected to external dependencies. For those situations, JOSS offers the InMemory implementation of the OpenStackClient.

    AccountConfig config = new AccountConfig()
            .setUsername( username)
    Account account = new AccountFactory(config).createAccount();

All the operations work basically in the same way. It is possible to run the in-memory client and have it hold the resources for a local run of your application.

Presumably, you are using Spring or something similar, in which case it will be easy to configure your profiles to either use the real client or the mock client.

This wraps up the tutorial. Good luck using JOSS.


JOSS provides access to the Container part of the OpenStack API. It is a specialized utility for this purpose. You will be able to:

  • access your account
  • handle containers
  • handle objects, including upload and download

Generally, Java developers want to be able to isolate their applications from the target servers during development, which is why JOSS support an in-memory mode. Simply have your application instantiate OpenStackClientInMemory (instead of OpenStackClientImpl) and you have a fully fledged in-memory Storage container, useful for testing your application on your own development system and isolating your application during various test stages.

Done and To-do

Things JOSS can do for you:

  • Java-based wrapper library for OpenStack, so REST calls do not have to be made directly
  • option to switch between real (ie, HTTPS target) and mock mode
  • in-memory storage of objects for unit testing and local application run purposes
  • auto-reconnecting your Swift session
  • documentation and tutorials to help you get started


Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

More information


On Cloud VPS Object Store

On the OpenStack API

Keep up to date on the library development by joining the Java OpenStack Storage discussion group Google Group

or follow us on Twitter

Special thanks to Oscar Westra van Holthe - Kind and Erik Hooijmeijer for premium advice and support.


This component was graciously donated by 42 BV 42 logo