Accessing and Modifying Mule Events10% of the exam
Enriching events with target and target value
How the Target and Target Value parameters on operations and Flow Reference store a result in a variable while the payload and attributes pass through unchanged, what the variable holds by default versus with `#[message]`, `#[attributes...]` or a selection, and how to read it later in DataWeave and in input parameters.
Apply correct processors/DataWeave expressions to enrich Mule events using Mule 4 connector targets, and predict outcomes.
~7 min read · 7 practice questions ·
What the exam expects
- Identify which processors accept a Target (non-void operations such as HTTP Request, File Read and Database Select, and Flow Reference) and which do not (Logger, Set Payload, Remove Variable).
- Predict the payload, the attributes and the target variable after an operation or Flow Reference with a target.
- Choose a Target Value: the default
payload,#[message],#[attributes.statusCode]or a selection such as#[payload[0].name], and write a valid target name. - Read a target variable later:
vars.name,vars.name.payloadfor a stored message, in a Transform Message or an operation's input parameters. - Key terms: Target (
target, name of the variable that stores the result); Target Value (targetValue, what to store, defaultpayload); enrichment (adding data to the event without replacing the payload); non-void operation (an operation that returns a message).
Key facts
Effect on the message
- Detail
- The next component receives the same message the operation received
Target Value default
- Detail
payload(the operation's result payload)
Target Value keywords
- Detail
payload,attributes,messageallowed;varsnot allowed
Target names
- Detail
- Numbers, characters and underscores only; no hyphens
Stored message
- Detail
targetValue="#[message]"; readvars.x.payloadandvars.x.attributes
Other variables
- Detail
- Variables the operation changed revert after it finishes
On error
- Detail
- Target variables are not set
Flow Reference target
- Detail
- Target Value evaluates against the referenced flow's output; caller's message unchanged
Flow Reference, no target
- Detail
- Payload and variable changes in the referenced flow persist
++ on objects- Detail
- Combines the key-value pairs of both objects into one
- Why does a Database Bulk Insert with
target="bulkInsertResult"leave the records as the payload? - Why do a referenced flow's variable changes disappear when the Flow Reference has a target?
- What happens to changes a referenced flow makes to the payload or variables when the Flow Reference has no target?
- When are target variables not set?
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