How to Resolve Jersey ModelValidationException: No Injection Source Found

What does it mean when I encounter a Jersey ModelValidationException stating 'No Injection source found'?

@GET
@Path("/example")
public Response getExample(@Context HttpServletRequest request) {
    // Implementation
}

The 'ModelValidationException: No Injection source found' error in Jersey usually indicates that the system is unable to identify the proper context or resource for dependency injection. This problem can arise due to misconfiguration or missing dependency mappings in your application’s setup.

@Path("/api")
public class MyResource {
    @Context
    private HttpServletRequest request;

    @GET
    @Path("/data")
    public Response getData() {
        // Use request object to get context
        // Implementation
    }
}

Causes

• The resource class is not annotated correctly with the appropriate context or request scope.
• The dependency injection framework is not initialized properly within the Jersey application.
• A mismatch in versioning between Jersey and any third-party libraries affecting injection.

Solutions

• Ensure that all resource classes are correctly annotated with @Path and any other required annotations (e.g., @Singleton, @RequestScoped).
• Verify that the injection constructor is defined correctly and matches the expected Jersey context requirements.
• Check for any missing configurations in your Jersey application setup files (e.g., web.xml) that may prevent proper context initialization.

Mistake: Omitting the @Context annotation from injected dependencies.

Solution: Always include the @Context annotation for any dependency that requires context injection.

Mistake: Forgetting to register the resource class with the Jersey application.

Solution: Ensure that your resource class is registered in your Application subclass or using the appropriate configuration.