Module 3 — DataWeave 2.0 Crash Course
Module 3 — DataWeave 2.0 Crash Course
This is probably the highest-value module for your interview.
DataWeave is MuleSoft’s transformation and expression language. It reads structured data, transforms it, and emits another structure or format. It is also used inside Mule expressions, not only inside full Transform Message components.
For your interview, think of DataWeave as:
JavaScript
.map(),.filter(), object construction, type conversion, and JSON/XML serialization combined into one language.
The syntax looks unusual for about an hour. Then it starts becoming predictable.
3.1The basic structureA DataWeave script usually looks like:3.2Your first transformationInput:3.3Salesforce field mappingExternal input:3.4Nested propertiesInput:3.5VariablesRemember Mule variables from Module 2:3.6DataWeave variables vs Mule `vars`Important interview distinction.3.7Arrays: the really important partSuppose payload is:3.8`$` shorthandDataWeave lets you write:3.9Real Salesforce bulk mappingIncoming:3.10FilteringInput:3.11Filter + mapThis is common.3.12`default`This is incredibly useful.3.13Null versus missing fieldThis matters in integration work.3.14Conditional valuesSimple example:3.15Conditional fieldsThis is different and extremely useful.3.16Another realistic conditional Salesforce mappingThis prevents accidental Salesforce field clearing.3.17Type conversion with `as`Incoming:3.18String → Number exampleInput:3.19DatesYou don't need to become a DataWeave date guru before the interview.3.20StringsYou'll frequently need basic cleanup.3.21String concatenationSuppose:3.22`mapObject`map transforms arrays.3.23`pluck`Useful mental model:3.24`flatten`Suppose:3.25`distinctBy`Integration developers frequently receive duplicate data.3.26`groupBy`Imagine orders:3.27Object merging with `++`++ isn't only string concatenation.3.28FunctionsYou can define reusable functions:3.29A more realistic reusable functionSay several fields need defaults:3.30Transform XML → JSONMule integrations aren't always JSON.3.31CSV → SalesforceInput:3.32A realistic Salesforce Account + Contact transformationInput:3.33Handling arrays of nested contactsNow Acme has several contacts:3.34Safe navigation / null handlingThis is where developers get bitten.3.35DataWeave isn't validationThis distinction will make you sound mature.3.36Salesforce relationship fieldsThis becomes important.3.37Transforming Salesforce query resultsSuppose Salesforce Query returns records conceptually like:3.38A DataWeave interview exerciseInterviewer gives you:3.39Harder exerciseInput:3.40What NOT to memorizeDon't spend tonight trying to memorize:•Your DataWeave survival setMemorize these:•Next: Module 4 — Salesforce ConnectorThis is where your existing experience becomes especially useful. We should cover Query, Query All, Create, Update, Upsert, Delete, SOQL…