The document discusses the Mule HTTP Listener connector in Mule. It defines a listener as an interface that handles events. The Mule HTTP Listener connector listens for HTTP requests and passes the request body and headers to the next flow element. The document provides steps to configure an HTTP listener in Mule by dragging it into a flow and using a set payload transformer to return a message. When a browser calls the flow, the HTTP Listener intercepts the request and returns the message set in the payload.

1. MULE
HTTP Listener tutorial

2. INDEX
What is a listener?
Mule HTTP Listener
Configure one in Mule
Result

3. What is a listener?
A listener is a class or method or interface or any implementation
which is responsible for handling a specific event. It can be any kind of
event like a remote procedure call, a method invocation or anything
like that.

4. Mule HTTP Listener
The HTTP Listener Connector provides the most practical way to listen for HTTP
requests.
The connector can be set up to accept any request, or to only accept requests that
are addressed to a very specific URI. You can choose what methods the connector
can accept (GET, POST, etc). The request body is passed on to the next element you
place in your flow as the message payload of a Mule Message, meanwhile headers,
query parameters, URI parameters and other elements of the HTTP Request are
passed on as inbound properties.

5. Configure one in Mule
Create a new project in Mule Anypoint Studio.
In the mule graphical editor drag and drop menu add HTTP listener to the
canvas. A new flow will be generated automatically. Following diagram depicts
the HTTP connector.
In my example I’ve setup a set payload mule transformer in the flow which will
return a particular message to the calling entity.

6. Result
 When there will be a call to this flow from browser, the Mule HTTP Listener will
intercept it and return the message that is set in payload by set payload mule
transformer.

7. Result
 When there will be a call to this flow from browser, the Mule HTTP Listener will
intercept it and return the message that is set in payload by set payload mule
transformer.