What is the failed validation?

Throws an error that is always a child of VALIDATION:VALIDATION.

What is the validate size?

Inclusive min (default 0) and max; String size is its length.

What is the is number?

Out-of-range or unparsable value throws VALIDATION:INVALIDNUMBER.

What is the is true / Is false?

Both throw VALIDATION:INVALIDBOOLEAN; expression defaults to false.

What is the all scope?

Runs every validation; any failure gives one VALIDATION:MULTIPLE.

What is the any scope?

VALIDATION:MULTIPLE only if all nested validations failed.

Routing Events8% of the exam

Validation module and idempotent message validation

Pick the right Validation module operation and predict the `VALIDATION:*` error it throws, combine checks with the All and Any scopes, and reject repeated messages with the Idempotent Message Validator and `MULE:DUPLICATE_MESSAGE`.

Official exam objective

Apply correct processors/syntax to validate Mule events, and predict outcomes.

~7 min read · 7 practice questions · updated Oct 28, 2026

What the exam expects

Choose the Validation operation that matches a rule (Is email, Is not blank string, Validate size, Is number, Is true) and write its XML with a custom message.
Predict the error a failed validation throws, and which type values on an On Error component catch it.
Predict the outcome of the All and Any scopes when some or all nested validations fail.
Configure the Idempotent Message Validator's idExpression and object store, and predict MULE:DUPLICATE_MESSAGE.

Key terms:

Validation operation: passes the event on or throws; never returns false.
VALIDATION:VALIDATION: the parent of every Validation module error type.
All / Any scope: group validations behind one VALIDATION:MULTIPLE error.
Idempotent Message Validator: lets only messages with an unseen ID continue.
idExpression: produces the message ID.

Key facts

Fact	Detail	Source
Failed validation	Throws an error that is always a child of `VALIDATION:VALIDATION`	Validation Module Documentation Reference (opens in a new tab)
Is not blank string	Throws `VALIDATION:BLANK_STRING`	Validation Module Documentation Reference (opens in a new tab)
Validate size	Inclusive `min` (default 0) and `max`; String size is its length	Validation Module Documentation Reference (opens in a new tab)Validation Module Examples 2.0 (opens in a new tab)
Is number	Out-of-range or unparsable value throws `VALIDATION:INVALID_NUMBER`	Validation Module Documentation Reference (opens in a new tab)
Is true / Is false	Both throw `VALIDATION:INVALID_BOOLEAN`; `expression` defaults to `false`	Validation Module Documentation Reference (opens in a new tab)
All scope	Runs every validation; any failure gives one `VALIDATION:MULTIPLE`	Validation Module Examples 2.0 (opens in a new tab)
Any scope	`VALIDATION:MULTIPLE` only if all nested validations failed	Validation Module Documentation Reference (opens in a new tab)
Idempotent `idExpression`	Defaults to `#[correlationId]`	Idempotent Message Validator (opens in a new tab)
Idempotent default store	Not persistent, entry TTL of 5 MINUTES	Idempotent Message Validator (opens in a new tab)
Duplicate message	Throws `MULE:DUPLICATE_MESSAGE`	Idempotent Message Validator (opens in a new tab)

Failed validation

Detail: Throws an error that is always a child of VALIDATION:VALIDATION
Source: Validation Module Documentation Reference (opens in a new tab)

Is not blank string

Detail: Throws VALIDATION:BLANK_STRING
Source: Validation Module Documentation Reference (opens in a new tab)

Validate size

Detail: Inclusive min (default 0) and max; String size is its length
Source: Validation Module Documentation Reference (opens in a new tab)Validation Module Examples 2.0 (opens in a new tab)

Is number

Detail: Out-of-range or unparsable value throws VALIDATION:INVALID_NUMBER
Source: Validation Module Documentation Reference (opens in a new tab)

Is true / Is false

Detail: Both throw VALIDATION:INVALID_BOOLEAN; expression defaults to false
Source: Validation Module Documentation Reference (opens in a new tab)

All scope

Detail: Runs every validation; any failure gives one VALIDATION:MULTIPLE
Source: Validation Module Examples 2.0 (opens in a new tab)

Any scope

Detail: VALIDATION:MULTIPLE only if all nested validations failed
Source: Validation Module Documentation Reference (opens in a new tab)

Idempotent idExpression

Detail: Defaults to #[correlationId]
Source: Idempotent Message Validator (opens in a new tab)

Idempotent default store

Detail: Not persistent, entry TTL of 5 MINUTES
Source: Idempotent Message Validator (opens in a new tab)

Duplicate message

Detail: Throws MULE:DUPLICATE_MESSAGE
Source: Idempotent Message Validator (opens in a new tab)

Sources for this section (3)

Check yourself

What does Validate size's min default to, and which kinds of value can it measure?
Why does setting the Idempotent Message Validator's Value Expression change nothing?
Why does an Is true operation with no expression configured fail?
Where do you find the error type each Validation operation throws?

The questions are free to read. Answers with their sources and self-grading are included with the pack.

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Core concepts
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What the exam expects

Key facts

Check yourself

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