![A diagram illustrates the process of converting a JSON payload to a string output](_images/using-dataweave-in-studio-8e6e0.png)
Graphically Construct a Mapping
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 diagram illustrates the process of converting a JSON payload to a string output](_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 diagram that displays the data fields for items and their respective data types](_images/using-dataweave-in-studio-6b171.png)
Set a Fixed Value or Function
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Double click on a field in the output tree. This adds a function icon
next to it.
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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:
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A fixed string value by using " ".
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A reference to an input field.
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A DataWeave statement that includes functions.
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