Duplicate property produced

[simopete]

Hi there,
I made a simple class with a @JsonProperty annotated private field named eSenseValues. The field has getter method named getESenseValues().
When I have serialized this class the json output had this field/property twice.
I think, it's a bug.

Here is my class and the json output:

import com.fasterxml.jackson.annotation.JsonProperty;
import java.io.Serializable;

public class WaveValues implements Serializable {

    @JsonProperty(value = "ESenseValues")
    private ESenseValues eSenseValues;

    public WaveValues() {
    }

    public ESenseValues getESenseValues() {
        return eSenseValues;
    }
}

{
  "WaveValues" : {
    "esenseValues" : {
      "attention" : 0,
      "meditation" : 0
    },
    "ESenseValues" : {
      "attention" : 0,
      "meditation" : 0
    }
  }
}

[cowtowncoder]

Ok. This is caused by Jackson's name discovery, which by default considers getESenseValues() to mean existence of property esenseValues. This is different from Java Bean introspection which would instead infer ESenseValues. With Java Bean name handling, you would only get a single property as you expect.

Jackson 2.5 did add MapperFeature.USE_STD_BEAN_NAMING, enabling of which gets handling you want. It is disabled by default for backwards-compatibility reasons.

Another alternative (and only choice if you are using an earlier version) would be to annotate getter with @JsonProperty as well; if so, field and getter would be properly coupled.

[simopete]

Thanks for your answer! I now understand the difference between Jackson and JavaBean serialization.
Before I wrote this issue I have looked at the wiki pages, but this feature isn't noted.
Can you write about it to the MapperFeature's wiki page or should I?

[cowtowncoder]

@simopete I can add that to Jackson github wiki page -- thank you for pointing it out. Feel free to send PRs for updates, fixes too of course, but I can take care of this one now.

[simopete]

Thank you for your work! I read the wiki again! It's good 👍