What's new in version 2.1


In the next sections, you will get a synthesis of the major changes done to the Restlet Framework in version 2.1.

For more details, you can read the the full list of changes.

Better documentation

Restlet in Action book

Finished writing the Restlet in Action book, published by Manning. We made sure that the printed version was available at the same time as the 2.1.0 release.

Scalable internal connector

Non blocking NIO

In version 2.0, we have added support for asynchronous processing of calls as a preview feature, including provisional responses (1xx status code in HTTP). This feature was only usable with the internal HTTP connector that is part of the Restlet engine (org.restlet.jar file), relying on message queues to support asynchronous handling. However, its IO processing was still done in a blocking manner, requiring two threads per connection which limits its scalability, even if persistent connections and pipelining and now supported.

There, we have started work on a new NIO version of this internal connector that leverages the non-blocking features of NIO to support a large number of concurrent connections and messages with only a single IO thread! The first results were very promising and we want to complete this connector in version 2.1 to replace the current internal connector with a lighter, faster and more scalable one.

SIP connector

SIP is a core protocol for Voice of IP (VoIP) to control multimedia session. It has been designed based on the HTTP protocol, using the same syntax for request and messages and with a similar processing flow, leveraging a lot provisional responses. We explored over the past months the possibility to provide a SIP connector based on the same internal connector that we use for HTTP and already we have a prototype working in the Restlet Incubator.

For version 2.1, we want to complete this initial work and make sure its works and scales properly on top of the new NIO based connector mentioned above. This will ship as an org.restlet.ext.sip extension. We also plan to explore a higher-level SIP application API that would provide a  REST-minded alternative to the SIP Servlets.

Security enhancements

Google SDC connector

This protocol allows tunnelling HTTP calls from a public cloud such as GAE, AWS or any other IaaS, to an intranet protected by a firewall, without requiring changes to this firewall.

Google App Engine extension

This extension integrates GAE’s authentication service with Restlet’s security API.

OAuth 2.0 and OpenID 2.0 extensions

See user guide for details.


Added to the Crypto extension.

Multipart HTML forms

The support for composite representations such as multi-part forms, on both the client and the server side is a recurrent need expressed by users, we should address it directly in the API or via an extension.

Currently, users rely on the FileUpload extension on the server-side and on alternative HTTP clients such as Apache HTTP Client 3.1 on the client-side. It would be much better to have a built-in consistent solution.

There will also be a focus on facilitating the validation of form submissions.

Conneg service

Content negotiation has always been a strong feature of the Restlet Framework. In version 2.0, its implementation and negotiation algorithm is fixed in the Restlet Engine. In this new version, we want to make it customizable via a new ConnegService.

Eclipse integration

Eclipse is more than an IDE and now provides a comprehensive runtime platform via the Eclipse RT project. In addition, OSGi and model-driven technologies developed by the Eclipse foundation nicely fit with the Restlet Framework. In version 2.1, we will help developers to bridge the Restlet and the Eclipse worlds.

Model-driven REST

Based on our experience with customers, we believe that the combination of Restlet and the pragmatic model-driven technologies developed by the Eclipse Modeling project adds a lot of value. In version 2.1, we will add those new related extensions:

  • EMF extension: to convert EMF representation beans into XML, XMI or HTML representations

Eclipse update site

In addition to our Maven repository, Zip archives and Windows installers, we want to add a possibility to install and update Restlet modules and dependent libraries via the Eclipse IDE directly. For this we will provide an update site. Restlet modules are already OSGi bundles so this should be straightforward.

Migration guide from version 2.0 to 2.1

This section intends to explain the main differences between the Restlet 2.0 and 2.1 releases and to help you migrate your existing applications. Both releases are meant to be compatible at the API level, so you should at most observe deprecate features while upgrading.

Note that if you intend to migrate directly from 1.1 to 2.1, you should really consider migrating first from 1.1 to 2.0 and then from 2.0 to 2.1. For migration instructions between 1.1 and 2.0, you can check this page.

Replace all JAR files

Restlet JARs and dependencies

Deprecated API features

The next step is to look at each deprecated feature and look in the Javadocs at the preferred alternative in version 2.1.