Many ESBs does not natively support REST, and may try to map or convert native REST calls into SOAP models. The UltraESB has been designed to support many different message formats natively, over multiple transports.
It supports all HTTP methods such as GET, PUT, DELETE, POST, OPTIONS, etc, and can even be extended to support other methods as well if required. By support both HTTP and HTTP, and HTTP authentication mechanisms such as Basic authentication, Digest authentication, Amazon AWS S3 Authentication and NTLM authentication, it can support any payload (XML, Text, Binary etc) extremely well, and handle thousands of concurrent connections with a few worker threads due to its ability to use Zero-copy proxying and Java Non-Blocking IO.
The UltraESB is possibly the fastest ESB around, and is available under the OSI approved AGPL License, as well as a Zero Dollar commercial license without any AGPL/GPL licensed artifacts.
The UltraESB distribution is around 30MB - including all documentation, samples and many optional libraries used to demonstrate the samples, and runs on both Windows and Linux/Unix environments, although other platforms that support JDK 1.6 and above maybe supported as well.
To get started with REST, it is suggested that the reader first follow the sample described here that shows the main HTTP methods used in REST being invoked, against a proxy service deployed on the UltraESB. The configuration forwards these requests to a RESTful service implemented with the RESTEasy framework from JBoss.
Check out the UltraESB samples index for more advanced examples, such as those demonstrating JTA XA transactions, mock services and using the UltraESB as a security gateway for REST services!