Find Workflow instance by WorkflowId

Let’s say I have two API endpoints:

POST /Executions
POST /Executions/{ExecutionId}

In the first, I create a new workflowClient.newWorkflowStub and use the option to define the workflowId and I return this Id back to the requester.

With the second API endpoint, I want to find this workflow instance so I can send data via a Signal.

Can you link me to some documentation please?

Use workflowClient.newWorkflowStub(<workflow class>, WorkflowId) to get a stub for an already running workflow:

FileProcessingWorkflow workflow = workflowClient.newWorkflowStub(FileProcessingWorkflow.class, workflowId);