I think, in general, GlassFish will tolerate a JAR with no manifest, but I'm not positive about that and it's not truly a valid JAR without one.
This particular part of GlassFish prepares to allow launching the app client using the automatic built-in support for Java Web Start. To do that, it needs to know all the JARs that the client depends on, either directly or indirectly. And to do that it needs to scan the manifest of each JAR so all the JARs on which the client indirectly depends are discovered.
In this case, a JAR without a manifest cannot refer to other JARs using its Class-Path (since that would appear in the missing manifest) so with the changes I've checked in this part of the server should tolerate the missing manifest. There could be other areas that I'm not aware of (or am not remembering) that might also have trouble with this.
I'd urge you to lean on the 3rd-party that provides the JAR to make it a valid JAR by including the manifest!
- Tim
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