Spring boot, Jackson Convert empty string into NULL in Serialization

Question

I have a requirement that while doing serialization I should be able to to convert all the properties that are with Empty string i.e "" to NULL, I am using Jackson in Spring boot, any idea how can I achieve this?

Can you provide more data, for list to json or the other way around? — Itsik Mauyhas
– Itsik Mauyhas, Commented Dec 26, 2019 at 17:35

Dmitry Ionash · Accepted Answer · 2019-12-26 22:47:58Z

4

Yep, it's very simple: use own Serializer for fields which can be empty and must be null:

class TestEntity {

    @JsonProperty(value = "test-field")
    @JsonSerialize(usung = ForceNullStringSerializer.class)
    private String testField;
}

class ForceNullStringSerializer extends JsonSerializer<String> {

    @Override
    public void serialize(String value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
        if (value == null || value.equals("")) {
            gen.writeNull();
        } else {
            gen.writeString(value);
        }
    }
}

This serializer can be applied to all fields where you need to return null.

answered Dec 26, 2019 at 22:47

Dmitry Ionash

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3 Comments

Muhammad Over a year ago

Thanks Lonash, Is there any way to use these on class level instead of each individual filed?

Dmitry Ionash Over a year ago

Yes, it is. But the logic in this case much more complex.

Muhammad Over a year ago

Dmitry, Would you like to give a hint how this can be done?

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