Jackson - way to define custom bean is empty for serialization

Question

What is the correct way to define a custom bean is empty for serialization by Jackson?

I want to filter unwanted fields by Json->POJO->Json. I suppose the custom bean object does not appear when serialize to JSON if all variables inside the custom bean object are null. If any variables inside is not null, the custom bean object should appear.

Currently, I have an extra method to assign null value to custom bean if all variables belongs to it are null. What I am looking for is if this could be done by Jackson.

public class JsonFileContext {

    //...Some variables

    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    @JsonView(Views.In.class)
    private ContentRecognize contentRecognize;

    //...getter/setter method
}

ContentRecognize class

public class ContentRecognize {

    @JsonInclude(JsonInclude.Include.NON_NULL)
    private String type;

    @JsonInclude(JsonInclude.Include.NON_NULL)
    private RecognizePattern targetId;

    @JsonInclude(JsonInclude.Include.NON_NULL)
    private RecognizePattern msgId;

    //...getter/setter method
}

Expected Output

{
    "var1":"var1Content",
    "var2":"var2Content"
}

AND

{
    "var1":"var1Content",
    "var2":"var2Content",
    "contentRecognize":{
        "type":"typeContent"
    }
}

Current Output

{
    "var1":"var1Content",
    "var2":"var2Content",
    "contentRecognize":{}
}

AND

{
    "var1":"var1Content",
    "var2":"var2Content",
    "contentRecognize":{
        "type":"typeContent"
    }
}

Could you please add the snip code of `ContentRecognize` class? — Tan Mai Van, Oct 11 '16 at 03:13
Try this - http://www.jsonschema2pojo.org/ to convert json into pojo class — Derrick, Oct 11 '16 at 03:43
Essentially you want to mark a property to be ignored at serialization by Jackson annotation, right? — Michal Foksa, Oct 11 '16 at 19:53
Or look at the http://stackoverflow.com/questions/39005703/jackson-annotations-difference-between-jsonignorepropertiesignoreunknown-true/39013609#39013609 where `password` is mentioned. — Michal Foksa, Oct 11 '16 at 20:31
@MichalFoksa What I suppose to do is not ignore the field, but to define the empty status of a custom bean such that the bean could be ignored if it is null or empty. — hk6279, Oct 12 '16 at 01:40

score 1 · Answer 1 · answered Oct 11 '16 at 20:19

You can use one of @JsonIgnoreProperties or @JsonIgnore annotations.

@JsonIgnoreProperties

Is used to ignore certain properties in serialization and deserialization regardless of its values:

to prevent specified fields from being serialized or deserialized (i.e. not include in JSON output; or being set even if they were included): @JsonIgnoreProperties({ "internalId", "secretKey" })

To ignore any unknown properties in JSON input without exception: @JsonIgnoreProperties(ignoreUnknown=true)

@JsonIgnore

Marker annotation that indicates that the annotated method or field is to be ignored by introspection-based serialization and deserialization functionality. That is, it should not be consider a "getter", "setter" or "creator".

In addition, starting with Jackson 1.9, if this is the only annotation associated with a property, it will also cause cause the whole property to be ignored: that is, if setter has this annotation and getter has no annotations, getter is also effectively ignored. It is still possible for different accessors to use different annotations; so if only "getter" is to be ignored, other accessors (setter or field) would need explicit annotation to prevent ignoral (usually JsonProperty).

In your case I would either of:

1:

@JsonIgnoreProperties({ "contentRecognize" })
public class JsonFileContext {
    [...]
}

2:

public class JsonFileContext {
    //...Some variables

    @JsonIgnore
    private ContentRecognize contentRecognize;

    //...getter/setter method
}

3: annotate contentRecognize getter with @JsonIgnore

Jackson - way to define custom bean is empty for serialization

1 Answers1