Apache Synapse - Lightweight ESB engine and XML router.
Apache Synapse is a simple and highly effective ESB, Web Services intermediary and SOA framework. It can be added to your existing network very simply either as a services gateway or as an HTTP proxy. Once Apache Synapse is mediating your service requests it can perform many functions including routing, load-balancing, transformation and protocol switching. Apache Synapse can be used to build an Enterprise Service Bus (ESB) or Service Oriented Architecture (SOA). Apache Synapse has been designed to support very fast XML routing with a streaming XML design based upon Apache Axiom. in addition, the use of a completely asynchronous architecture and non-blocking IO based on Java NIO ensures that Synapse has very low overhead and can scale to support thousands of concurrent clients without dropping messages.