How to ignore field totally by its value when serializing with Jackson with annotation on that field?

问题

Almost the same question but the accepted answer does not fit the general need. Having Simple class and custom serializer like:

Example class

@Getter
@Setter
public class ExampleClass {
    @JsonInclude(JsonInclude.Include.NON_NULL)
    @JsonSerialize(using = StringSerializer.class)
    private String stringNull;        
    @JsonInclude(JsonInclude.Include.NON_NULL)
    @JsonSerialize(using = StringSerializer.class)
    private String stringOk = "ok";
    @JsonInclude(JsonInclude.Include.NON_NULL)
    @JsonSerialize(converter = StringSerializer.class)
    private String stringNotOk = "notOk";        
}

Custom serializer

@SuppressWarnings("serial")
public static class StringSerializer extends StdSerializer<String> {
    public StringSerializer() {
        super(String.class);
    }
    @Override
    public void serialize(String value, JsonGenerator gen, SerializerProvider serializers) 
            throws IOException {
        if(value != null && value.equals("ok")) {
            gen.writeString(value);
        }
    }
}

So I only want to print out elements that are equal to "ok" but if not equal to "ok" I do not want to print anything. Works fine except for stringNotOk. When calling ObjectMappper like:

new ObjectMapper().writeValueAsString(new ExampleClass());

it produces "bad" JSON:

{"stringOk":"ok","stringNotOk"}

Is there any other way or can I can avoid to raise the serializer to class level and create it separately for each class having such field na taking account field name etc...?

Can I - for example - somehow "revert" back and remove the name "stringNotOk" from already written JSON?

How could this be made in a generic way so that just one serializer and an annotation on needed fields were used?

回答1:

I think you are looking for something like

@JsonInclude(value = JsonInclude.Include.CUSTOM, valueFilter = OkFilter.class)

public class OkFilter {

  @Override
  public boolean equals(Object obj) {
     //your logic for finding 'ok' value here
  }
}

Here you can read more about this https://www.logicbig.com/tutorials/misc/jackson/json-include-customized.html

来源：https://stackoverflow.com/questions/62542799/how-to-ignore-field-totally-by-its-value-when-serializing-with-jackson-with-anno

标签

java

serialization

jackson