ESIGate

ESIGate is a website assembling toolkit. It was created by a number of specialist J2EE engineers at Smile, the leading European integrator of open source solutions.

ESIGate acts like a reverse proxy for existing websites and webapps, whose HTML pages it can retrieve, convert and reassemble on the fly. The various bits of pages obtained from different servers are then served to the user as if they came from a single website. The major strength of this approach is the fact that it is technologically agnostic, capable of integrating any PHP, .NET or Java web application with no, or very few, modifications to that application (just the addition of ESI tags).
ESIGate is distributed under the Apache License. It is currently the only complete open source implementation of the W3C's Edge Side Include standard (other tools like Varnish offer partial implementations). ESIGate is written in Java and includes an API, as well as various extension points that make it possible to adapt it to each project's needs and to the special features of integrated solutions (cookie management, Single Sign On, URL rewriting and more).