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On submission of this form, we would like to start a process instance for each of the rows from this grid.
We would like to start a process instance of the process definition "travel_approver_process".
We will need to pick up the grid data by matching the current batch record ID in gda_batch and list down records from gda_travel.
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In the batch form itself, we can make use of "Post Form Submission Processing" to capture event of "Data Creation" or "Both data creation and update", whichever suits your own use case, to execute bean shell Java code to achieve this.
Bean shell Java code to iterate through grid data and start a process instance for each of the rows.
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