APT ignores @Inject fields in superclass when generating Mvc route constructors

[goodcwj]

When a controller extends a base class that contains @Inject fields, but the controller itself does not define any @Inject-annotated fields or constructors, the Jooby APT–generated _ router class does not instantiate the controller through the DI container.

Instead, it falls back to new, which bypasses dependency injection. As a result, injected fields inherited from the superclass are null.

example

public abstract class ApiRouteBase {
  @Inject
  protected AdminParamDecoder paramDecoder;
}

Controller:

@Path("/reports")
public class ReportsApi extends ApiRouteBase {
  @GET
  public Object list(Context ctx) {
    return paramDecoder.decodeAdminRequest(ctx);  // paramDecoder is null
  }
}

Runtime response:

{
  "httpCode": 500,
  "httpMessage": "Server Error",
  "type": "internal",
  "userMessage": "Internal error",
  "internalMessage": "Cannot invoke ... because \"this.paramDecoder\" is null"
}

Observed behavior in generated _ router class:

io.jooby.SneakyThrows.singleton(ReportsApi::new)

instead of

ctx.require(ReportsApi.class)

So the controller does not receive DI for the inherited field.

Workarounds##

Add a constructor with @Inject in the controller:

@Inject
  public ReportsApi() {
  }

After doing this, paramDecoder is correctly injected.