In ServiceBus 12c you get a 'composite'-alike service overview for your project. It shows you how the proxy services (like Exposed Services in SOASuite) via pipelines are 'wired'to business services (like Referenced Services). This is nice!

If you upgrade a project from 11g or 12cR1 (12.1.3) to 12cR2 (12.2.1) this fails. Initially you might see a (correct) diagram, but after restarting JDeveloper this is empty. You'll get a Class cast exception:

java.lang.ClassCastException: oracle.tip.tools.ide.fabric.addin.CompositeNode cannot be cast to oracle.sb.tooling.ide.sca.internal.sca.SbCompositeNode
at
oracle.sb.tooling.ide.sca.internal.sync.CompositeEditorListener.editorOpened(CompositeEditorListener.java:72)

Also after opening a earlier upgraded project, OSB diagrams fail to open and instead generate this java.lang.ClassCastException.
I search on support.oracle.com  and found this document: 'Unable to open OSB Diagrams upgraded from 12.1.3 to 12.2.1 (Doc ID 2124208.1)'
It refers to the patch:

• 22226040: java.lang.NullPointer for XQuery File ver 1.0 in JDEV 12.2.1 OSB Proj

 Apply this patch (for instance via my patch script in my previous article). The document suggests to backup and remove the user-data folder of your JDeveloper QuickStart installation. I found that not necessary. But you do need to re-import the projects from the earlier versions. I would empty the .data folders on application and project levels before starting JDeveloper again. Then delete the upgraded projects and reimport them again. Now after restarting JDeveloper the overviews should remain.