Session Variable in Mule
Use a session variable transformer to set or remove a variable that is tied to a message for its entire lifecycle, potentially across multiple flows, applications, and even servers. Session variables can be easily propagated from one flow to another through the VM transport, or a flow reference, but not through the HTTP Connector. By contrast, variables specified through the variable transformer persist only as long as the message with which they are associated remains within the same flow.
Session variables cannot cross all transport barriers, but in some cases, they can cross barriers and become accessible in another flow.
Example: Session Variables cannot cross HTTP CONNECTOR but they can cross VM CONNECTOR.
Session variable is accessible by : #[sessionVars.variablename]
In dataweave flow variable is accessible by : sessionVars.variablename
Here is basic flow for session variable and here we can see session variable is accessible in subflow and again in main flow when control goes back to main flow. It is also accessible in transform message component as mentioned in code below.
URL : http://localhost:8085/api/sessionvar
Method : GET
XML project code :
<?xml version="1.0" encoding="UTF-8"?>
<mule xmlns:tracking="http://www.mulesoft.org/schema/mule/ee/tracking" xmlns:vm="http://www.mulesoft.org/schema/mule/vm" xmlns:dw="http://www.mulesoft.org/schema/mule/ee/dw" xmlns:http="http://www.mulesoft.org/schema/mule/http" 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"
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/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
http://www.mulesoft.org/schema/mule/ee/dw http://www.mulesoft.org/schema/mule/ee/dw/current/dw.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/ee/tracking http://www.mulesoft.org/schema/mule/ee/tracking/current/mule-tracking-ee.xsd">
<http:listener-config name="HTTP_Listener_Configuration" host="0.0.0.0" port="8085" basePath="/api" doc:name="HTTP Listener Configuration"/>
<vm:connector name="VM" validateConnections="true" doc:name="VM"/>
<flow name="testsessionvarFlow">
<http:listener config-ref="HTTP_Listener_Configuration" path="/sessionvar" doc:name="HTTP"/>
<set-session-variable variableName="sessionvar" value="Himanshu" doc:name="Session Variable"/>
<logger message="Value of Session var is : #[sessionVars.sessionvar]" level="INFO" doc:name="Logger"/>
<flow-ref name="testsessionvarSub_Flow" doc:name="testsessionvarSub_Flow"/>
<logger message="Logger back in main flow : #[sessionVars.sessionvar]" level="INFO" doc:name="Logger"/>
<dw:transform-message doc:name="Transform Message">
<dw:set-payload><![CDATA[%dw 1.0
%output application/json
---
{
var1 : sessionVars.sessionvar
}]]></dw:set-payload>
</dw:transform-message>
<logger message="Dataweave output is : #[payload]" level="INFO" doc:name="Logger"/>
<set-payload value="#[payload]" doc:name="Set Payload"/>
</flow>
<sub-flow name="testsessionvarSub_Flow">
<logger message="Value of Session variable in subflow is : #[sessionVars.sessionvar]" level="INFO" doc:name="Logger"/>
</sub-flow>
</mule>
Session variable example using VM Connector :
URL : http://localhost:8085/api/sessionvm
Method : GET
XML project code :
<?xml version="1.0" encoding="UTF-8"?>
<mule xmlns:tracking="http://www.mulesoft.org/schema/mule/ee/tracking" xmlns:vm="http://www.mulesoft.org/schema/mule/vm" xmlns:dw="http://www.mulesoft.org/schema/mule/ee/dw" xmlns:http="http://www.mulesoft.org/schema/mule/http" 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"
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/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
http://www.mulesoft.org/schema/mule/ee/dw http://www.mulesoft.org/schema/mule/ee/dw/current/dw.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/ee/tracking http://www.mulesoft.org/schema/mule/ee/tracking/current/mule-tracking-ee.xsd">
<http:listener-config name="HTTP_Listener_Configuration" host="0.0.0.0" port="8085" basePath="/api" doc:name="HTTP Listener Configuration"/>
<vm:connector name="VM" validateConnections="true" doc:name="VM"/>
<flow name="testsessionvarFlow1">
<http:listener config-ref="HTTP_Listener_Configuration" path="/sessionvm" doc:name="HTTP"/>
<set-session-variable variableName="sessionvar" value="Himanshu" doc:name="Session Variable"/>
<vm:outbound-endpoint exchange-pattern="request-response" path="vmpath" doc:name="VM"/>
<logger message="Session variable value back in main flow : #[sessionVars.sessionvar]" level="INFO" doc:name="Logger"/>
<set-payload value="#[payload]" doc:name="Set Payload"/>
</flow>
<flow name="testsessionsubFlow">
<vm:inbound-endpoint exchange-pattern="request-response" path="vmpath" doc:name="VM"/>
<logger message="Session variable in VM flow : #[sessionVars.sessionvar]" level="INFO" doc:name="Logger"/>
</flow>
</mule>