Use of anchors in Dropwizard Configuration

[sjames...@gmail.com]

Hi

I would like to use anchors in my Dropwizard configuration file.

For example:

schedules:
 ScheduleA: &id001

    commands:

      - type: event

        name: Event1

      - type: delay

        period: 1m

# Detail omitted...

nodes:
 - address: 127.0.0.1
   schedule: *id001

However, the parser objects:

emu.yml has an error:

  * Failed to parse configuration at: nodes.schedule; Can not instantiate value of type java.lang.String from String value; no single-String constructor/factory method (through reference chain: com.company.EmulatorConfiguration["nodes"]->com.company.NodeConfiguration["schedule"])

Is this is an issue with the version of jackson that Dropwizard is using?

Thanks.

Simon

[Justin Miller]

Have you tried wrapping *id001 with ""?

> --
> You received this message because you are subscribed to the Google Groups
> "dropwizard-user" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to dropwizard-us...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.

[sjames...@gmail.com]

I had not tried that, but I have now and I get the same error.

[Justin Miller]

Can you post the configuration code?

[sjames...@gmail.com]

I’m assuming you mean the Java code.

Somewhat simplified, I have:

public class EmulatorConfiguration extends Configuration {

    @NotEmpty
    @JsonProperty("nodes")
    private List<NodeConfiguration> nodes;

    @JsonProperty
    private Map<String, Schedule> schedules;

}

public class Schedule {

    @NotEmpty
    @JsonProperty
    private List<ScriptCommand> commands;
}

public class NodeConfiguration {

    @NotEmpty
    private String address;

    @JsonProperty
    private Schedule schedule;

}

[sjames...@gmail.com]

I should have added that I have tried this with versions 0.7.0 and 0.7.1 of Dropwizard.

[Tatu Saloranta]

First: to have any support for YAML anchors and references, Jackson 2.4 must be used; this version supports used of YAML's native object and type id constructs.

Unfortunately this is not quite enough to yet support anchors, since Jackson databind also needs to be aware of possible Object Ids. This means that value types in question need to enable object id support with @JsonIdentityInfo.

I have not tried using this yet, but theoretically it should work.

So in this example, @JsonIdentityInfo should be added to type Schedule.

I would be interested in knowing if this works, or if not, what error is being given.

One open question is what happens to instances without anchor.

-+ Tatu +-