JsonSchemaValidator fails to load schema in OSGi environments

[tim-schneider-elo]

Bug description
When I try to run the MCP Server with version 2.0.0-M3 it does not start, because it can't find the schema.

 SchemaRegistry :775 |  Failed to load json schema from https://json-schema.org/draft/2020-12/schema
java.io.FileNotFoundException: classpath:draft/2020-12/schema
        at com.networknt.schema.resource.ClasspathResourceLoader.lambda$getResource$0(ClasspathResourceLoader.java:75)
        at com.networknt.schema.SchemaRegistry.getMappedSchema(SchemaRegistry.java:749)
        at com.networknt.schema.SchemaRegistry.loadSchema(SchemaRegistry.java:734)
        at com.networknt.schema.SchemaRegistry.getSchema(SchemaRegistry.java:649)
        at io.modelcontextprotocol.json.schema.jackson3.DefaultJsonSchemaValidator.<init>(DefaultJsonSchemaValidator.java:54)

Environment
SDK: 2.0.0-M3

Steps to reproduce

• Try to start the server

Expected behavior

• Server should start normally

[tzolov]

@tim-schneider-elo , could you please elaborate on this issue and explain how to reproduce it?

[tim-schneider-elo]

I had a running project with an MCP Server running as an OSGI-Bundle

I updated the dependency to use version 2.0.0-M3, now it fails to start the plugin, because the server throws this error message I mentioned. I changed nothing else

My code/project works with version 2.0.0-M1, 2.0.0-M2, but not with 2.0.0-M3 and 2.0.0-RC1.

[chemicL]

@tim-schneider-elo thanks for explaining. I changed the name to highlight that this is a problem for OSGi. I am not certain if this is a java-sdk specific problem or com.networknt.schema issue. This seems to be caused by loading the 2020-12 schema definition required in order to validate by default the specific dialect as the spec requires (#700).

Also, isn't this fixed by the way by #948? If so, we can close as duplicate. Please confirm with 2.0.0 which we released today.

[tim-schneider-elo]

I did try it with the release 2.0.0 but it still fails.

We don't use the Import/Export-Package functionality properly, so I don't think it has to do with #948
We include everything in the Bundle-Classpath

[Kehrlann]

This seems to be classloader issue.

Providing a reproducing project would help us debug. My coding agent suggests using the lib's ClassLoader itself:

this.schemaFactory = SchemaRegistry.withDefaultDialect(Dialects.getDraft202012(),
    builder -> builder.resourceLoaders(rl ->
        rl.add(new ClasspathResourceLoader(ClasspathResourceLoader.class::getClassLoader))
    )
);

It does not break my build locally, but I don't know if it would fix your specific issue.

edit: tagging @tim-schneider-elo