Synapse handler is new feature which come with the ESB 4.9.0. It provide abstract handler implementation to the users. User can create their own concrete handlers which is executing in the synapse layer. Main intention of this blog post is to explain how to write synapse handler and explain basic theoretical background. 1. What is the handler? Handlers are basically talking with the chain of responsibility pattern. Chain of responsibility allows a number of classes to attempt to handle a request independently of any other object along the chain. Once the request is handled, it completes it's journey through the chain. The Handler defines the interface which required to handle the request and concreteHandlers handle request in a specific manner that they are responsible for. 2. What is Synapse handler? Synapse handler is providing abstract handle implementation which executes in the following four scenarios. 1. Request in flow This is exe