Reviewing and Changing the Assigned Source for an Operation Parameter
Designer assigns each parameter a source. The source value for a parameter indicates how the input parameter is sent in a request. Designer usually assigns operation parameters a source of FORMDATA, except in the following situations:
If an input parameter for a service associated with a resource operation is a document or a document reference,
Designer assigns the parameter a source of BODY.
For a REST V2 resource, if an input parameter for a service associated with the resource operation is referenced as a dynamic parameter in the URL format,
Designer assigns the parameter a source of PATH. If the input parameter is referenced as a static parameter in the URL format,
Designer assigns the parameter a source of HEADER.
When you add a REST resource to a REST API descriptor, you should verify that each parameter uses the source value that matches the service implementation exposed by the operation.
Important:
For a REST API descriptor containing resources created using the legacy approach, you cannot change the assigned source for a parameter if the source value is BODY. For a REST API descriptor containing REST V2 resources, you cannot change the assigned source for a parameter if the value is either BODY or PATH.
To review and change the source for a parameter
1. In the Package Navigator view, lock and open the REST API descriptor that contains the REST resource operation for which you want to change the parameter source.
2. Click the REST Resources tab.
3. Expand the REST resource for which you want to view and change the parameter source.
4. Expand the operation for which you want to view and/or change the assigned source.
5. Click 
Parameters. Designer displays the parameters for the operation.
6. To change the source for a parameter, click the cell for the parameter in the Source column and select the source you want to assign to the parameter.
7. Repeat step 6 for each parameter in the operation.
8. Click File > Save.