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title: Graphically Construct a Mapping (Anypoint Studio)
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# Graphically Construct a Mapping (Anypoint Studio)

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

Through the graphical UI of the Transform Message component you can do the tasks below. When doing
each, the necessary lines are added to the DataWeave code to describe the action.

## Map a Field

Drag an element on the input structure over to another on the output structure, this casts a line
that joins them.

![A JSON input and output structure](/mulesoft/current/en-us/mule-runtime/4.9/_images/using-dataweave-in-studio-8e6e0.png)

## Map a Structure

Drag a high-level structure that contains lists of elements or inner fields onto another in the
output. This creates a shaded region covering all the mapped structure. Fields that have identical
names in these structures are automatically mapped too.

![A list of items with fields including ItemID and DeliveryMethod](/mulesoft/current/en-us/mule-runtime/4.9/_images/using-dataweave-in-studio-6b171.png)

## Set a Fixed Value or Function

1.  Double click on a field in the output tree. This adds a function icon
    ![Function icon](/mulesoft/current/en-us/mule-runtime/4.9/_images/using-dataweave-in-studio-66cdc.png) next to it.

2.  A new line is added to the DataWeave code that assigns a default `null` value to the field. This
    line is highlighted. Change its value to anything you want.

You can add:

- A fixed string value by using " ".

- A reference to an input field.

- A DataWeave statement that includes functions.

## See Also

- [Transform Message Component](https://docs.mulesoft.com/mule-runtime/4.9/transform-component-about)

- [Workflow: Create a Mapping](https://docs.mulesoft.com/mule-runtime/4.9/transform-workflow-create-mapping-ui-studio)

- [DataWeave Language](https://docs.mulesoft.com/mule-runtime/4.9/dataweave)