1. Go to em console page and navigate to Deployed Composites.
Click on the Composite that you want to export.
Click on the Composite Drop down menu and click Export.
In the next screen, leave the default options and click on "Export" button.
It'll generate the jar file.
Click on Save File after the jar file is ready.
2. Now, import the file from your JDeveloper. Click on the File>Import.
Select SOA Archive Into SOA Project option and click OK.
Give it a name and click Next.
In the Composite Archive, browse the location where your jar file is located and click Finish. Now you can view the composite in JDeveloper and see the flow.
Happy learning. Cheers!!