This document demonstrates how to use expression filters in Mule applications. It shows an example Mule configuration file with two flows, one that sets a session property and logs it, and another that is called conditionally by the first flow via a VM endpoint based on the expression filter evaluation of the session property. The output log shows the session property being set and logged in both flows, demonstrating the expression filter functionality.

1. Expression Filter In Mule Demo

2. Abstract
• The main motto of this PPT is how to use
Expression filter in our applications.

3. Example

4. • .mflow
• <?xml version="1.0" encoding="UTF-8"?>
• <mule xmlns:tracking="http://www.mulesoft.org/schema/mule/ee/tracking" xmlns:http="http://www.mulesoft.org/schema/mule/http"
xmlns:vm="http://www.mulesoft.org/schema/mule/vm" xmlns="http://www.mulesoft.org/schema/mule/core"
xmlns:doc="http://www.mulesoft.org/schema/mule/documentation" xmlns:spring="http://www.springframework.org/schema/beans" version="EE-
3.4.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-current.xsd
• http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
• http://www.mulesoft.org/schema/mule/vm http://www.mulesoft.org/schema/mule/vm/current/mule-vm.xsd
• http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
• http://www.mulesoft.org/schema/mule/ee/tracking http://www.mulesoft.org/schema/mule/ee/tracking/current/mule-tracking-ee.xsd">
• <flow name="MessagePropertiesFlow1" doc:name="MessagePropertiesFlow1">
• <http:inbound-endpoint exchange-pattern="request-response" host="localhost" port="8089" path="expressionfilter" doc:name="HTTP"/>
• <message-properties-transformer scope="session" doc:name="Message Properties">
• <add-message-property key="property1" value="mule studio"/>
• </message-properties-transformer>
• <logger message="--flow1--#[sessionVars['property1']]" level="INFO" doc:name="Logger"/>
• <expression-filter expression="#[sessionVars['property1']!='mule']" doc:name="Expression"/>
• <vm:outbound-endpoint exchange-pattern="request-response" path="messageproperties" doc:name="VM"/>
• </flow>
• <flow name="MessagePropertiesFlow2" doc:name="MessagePropertiesFlow2">
• <vm:inbound-endpoint exchange-pattern="request-response" path="messageproperties" doc:name="VM"/>
• <logger message="---flow2--#[sessionVars['property1']]" level="INFO" doc:name="Logger"/>
• </flow>
• </mule>

5. • Output:
• INFO 2015-10-03 16:00:23,705 [[messageproperties].config.change.14.thread.1] org.mule.DefaultMuleContext:
• **********************************************************************
• * Application: messageproperties *
• * OS encoding: Cp1252, Mule encoding: UTF-8 *
• * *
• * Agents Running: *
• * Clustering Agent *
• * JMX Agent *
• **********************************************************************
• INFO 2015-10-03 16:00:23,706 [[messageproperties].config.change.14.thread.1]
org.mule.module.launcher.MuleDeploymentService:
• ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
• + Started app 'messageproperties' +
• ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
• INFO 2015-10-03 16:00:26,480 [[messageproperties].connector.http.mule.default.receiver.02]
org.mule.api.processor.LoggerMessageProcessor: --flow1--mule--studio
• INFO 2015-10-03 16:00:26,482 [[messageproperties].connector.http.mule.default.receiver.02]
org.mule.lifecycle.AbstractLifecycleManager: Initialising: 'connector.VM.mule.default.dispatcher.771015974'.
Object is: VMMessageDispatcher
• INFO 2015-10-03 16:00:26,482 [[messageproperties].connector.http.mule.default.receiver.02]
org.mule.lifecycle.AbstractLifecycleManager: Starting: 'connector.VM.mule.default.dispatcher.771015974'. Object
is: VMMessageDispatcher
• INFO 2015-10-03 16:00:26,489 [[messageproperties].connector.http.mule.default.receiver.02]
org.mule.api.processor.LoggerMessageProcessor: ---flow2--mule--studio

6. • Flow of execution:
1. URL to trigger the service from browser
http://localhost:8089/expressionfilter
2. session property is created using message
property component In flow1
3. Service displays session properties in flow1
4. VM component in flow1 will call flow2 if the
value of the session property is other then mule.
5. In the POC the session property value is “mule
studio” so flow1 calls flow2 and displays session
property value in flow2

7. References
• https://docs.mulesoft.com/mule-
fundamentals/v/3.7/mule-filters-scopes-and-
routers