This document discusses how to use expression filters in Mule ESB to filter messages based on query parameter values. An expression filter is configured on an HTTP inbound endpoint to only allow messages through if the "name" query parameter equals "User". Postman tests are run to verify that messages are passed or blocked based on the name parameter.

1. Mule ESB
How to use Expression Filters

2. In this tutorial we will be using the expression filter, which is a filter against a range of
expressions.
As usual, let’s begin creating the http inbound component to trigger the flow
The goal is to send a query param called ‘name’, with a value based on which the flow will
continue or end after the http inbound component

3. For this purpose we will use the ‘expression filter’ configured in the following way:
Expression: #[message.inbounfProperties.’http.query.params’.name == ‘User’]
The meaning of the expression is to let the incoming messages pass through the filter only
if the expression is evaluated to true. In this case, so, if the passed ‘name’ param value is
set to ‘Gennaro’.
Let’s add a set Payload and a logger to see the results, and show the message pass through
the filter. Settings: Value = User Passed!

4. Let’s dive into postman to test it out.
Test #1. Message not passed:
Test #2. Message passed:
User Passed!
ENJOY WITH THE MULE!