The VM transport in Mule allows for asynchronous communication within a JVM using in-memory queues. Messages can be delivered directly between request-response endpoints or through non-blocking queues. The document demonstrates creating two flows, one that receives an HTTP request and sends the payload to a VM queue, and another that receives messages from the same VM queue and logs the payload.

1. VM TRANSPORT
VM Transport is based on in-memory Queues
available within Mule JVM. These can also be
persisted to Files should we require more
reliable storage. These are just like JMS
Queues

2. • The in memory (VM) transport has two modes of
operation: One for use with request-response and another
for use with one-way endpoints.
• request-response:
• When using request-response endpoints, messages are
delivered directly from an outbound vm endpoint to the
inbound vm endpoint that is listening on the same path.
This delivery is blocking and occurs in the same thread.
• one-way:
• When using one-way endpoints, messages are delivered
to the corresponding inbound endpoint via a queue. This
delivery is non-blocking.

3. • Asynchronous communication is desired but external
message broker (such as Active MQ) can’t be used. This
can be for for performance or non-availability reasons.
• Create VM endpoints.
• Messages will be received on inbound endpoints.
• Messages will be sent to outbound endpoints.
• Both kinds of endpoints are identified by a path name or
address.

4. Lets create an example to understand how VM transport works.
• Create a HTTP inbound endpoint with port as “8081” and
path as “vm”. Then drag and drop a VM endpoint next to
HTTP. Select “request-response” as exchange pattern.
Also, specify “VM1” as Queue Path.
• Drag and drop another VM endpoint below
vmdemoFlow1. Mule Studio automatically creates another
flow named vmFlow2. Select “request-response” as
exchange pattern. Also, specify “VM1” as Queue Path.
This ensures messages passed from vmFlow1 are read in
vmdemoFlow1 since Queue paths are same.

5. vmdemoflow

6. Http configuration

7. Set Payload configuration

8. XML code
• <?xml version="1.0" encoding="UTF-8"?>
• <mule xmlns:vm="http://www.mulesoft.org/schema/mule/vm"
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/vm http://www.mulesoft.org/schema/mule/vm/current/mule-vm.xsd">
• <http:listener-config name="HTTP_Listener_Configuration" host="0.0.0.0" port="8081" doc:name="HTTP
Listener Configuration"/>
• <flow name="vmdemoFlow">
• <http:listener config-ref="HTTP_Listener_Configuration" path="vm" doc:name="HTTP"/>
• <set-payload value="Hello" doc:name="Set Payload"/>
• <vm:outbound-endpoint exchange-pattern="request-response" path="VM1" doc:name="VM"/>
• </flow>
• <flow name="vmdemoFlow1">
• <vm:inbound-endpoint exchange-pattern="request-response" path="VM1" doc:name="VM"/>
• <set-payload value="#[message.payload]......MULE" doc:name="Set Payload"/>
• <logger message="#[message.payload]" level="INFO" doc:name="Logger"/>
• </flow>
• </mule>

9. Output:Using the url
http://localhost:8081/vm

10. Http://localhost:8081/vm
• If it is a one-way communication
• We can get the following output
“Hello” only