A Mule4 message is composed of a payload and its attributes. Mule event is immutable, so every change to an instance of a Mule event results in the creation of a new instance.
A Mule 4 Event is composed of these objects:
While we have already seen in Mule 3, Mule message is, itself, embedded within a Mule message object and it may contain variables, attachments, and exception payloads.
In Mule 3, When the request is received by Mule message source. It is then converted into a Mule message or flow and starts processing it when it receives an inbound endpoint in a flow.
In Mule 4, flows triggered by an event are generated when a trigger reaches the event source of flow. This trigger could be an external event triggered by a resource that might be external to the Mule app.
You can create, or update, variables in these ways:
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Using the Set Variable component.
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Using a Target Variable from within an operation, such as the Read operation to the File connector or the Store operation to the Database connector.
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Using the Datwave Transform Component (EE-Only).
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Using Scripting Component (in scripting module)
You can also delete/remove:
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Using the Remove Variable component.
After creating a variable, you can access and use it within the scope of a Mule flow where you created it, which includes any flows that are joined with it through a Flow Ref component.
vars: Keyword for accessing a variable, for example, if the name of your variable is myVar, you can access it like this:vars.myVar
Message Collections:
One of the major changes to the new Mule Message structure is when dealing with collections. In Mule 3, components that returned multiple payloads, used a special structure called the
MuleMessageCollection. But in Mule 4, any component that needs to deal with multiple messages can simply set the payload of the message to a List of Mule Messages. We can then iterate over these messages using DataWeave, For Each, or other components based on requirement.Comparison between Mule 3 Structure and Mule 4 Structure
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Mule 3
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Syntax
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Mule 4
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Syntax
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Description
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Mule Message
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#[message]
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Simplified
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#[message]
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Consists of payload and attributes
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Inbound properties
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#[message.inboundProperties.’http.version’]
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Replaced by Attributes
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#[attributes.header]
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Replaced with attributes and have advantage that we can store it in variables to access throughout your flow.
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Outbound properties
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#[message.outboundProperties.’MULE_ENCODING’]
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Removed
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We can achieve it by using dataweave expression.
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Flow Variables
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#[flowVars.varName]
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Replaced
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#[vars.varName]
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Replaced with variables but acts same as Mule 3
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| Session Variables |
#[sessionVars.varName]
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removed | | Removed as transport barriers are no more exists. We can store values in variables itselves. |
| Record Variables |
#[recordVars.varName]
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removed | | Removed as batch jobs is a scope which lives inside flow, we can store in variables. |
| Attachements |
#[message.inboundAttachements]
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removed | |
Inbound and outbound attachments have been removed. The affected connectors now handles the attachment using Dataweave.
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List of predefined keyword used in
- vars
- app
- attributes
- authentication
- correlationId
- dataType
- error
- message
- mule
- payload
- server
Happy Learning 🙂
Happy Learning 🙂
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Nice article…!