Why jackson is serializing transient member also?

Question

I am serializing a POJO into JSON using Jackson 2.1.4 but I want to ignore a particular field from getting serialized. I used transient but still it is serializing that element.

public class TestElement {

    int x;

    private transient String y;

    public int getX() {
        return x;
    }

    public void setX(int x) {
        this.x = x;
    }

    public String getY() {
        return y;
    }

    public void setY(String y) {
        this.y = y;
    }
}

I am serializing as following:

public static void main(String[] args) throws JsonProcessingException {
    TestElement testElement = new TestElement();
    testElement.setX(10);
    testElement.setY("adasd");
    ObjectMapper om = new ObjectMapper();
    String serialized = om.writeValueAsString(testElement);
    System.err.println(serialized);
}

Please don't suggest @JsonIgnore as I don't want to tie my model to jackson specific annotations. Can it be done using transient only? Is there any API on objectmapper for visibility settings?

score 77 · Accepted Answer · edited Jan 14 '21 at 09:49

77

The reason Jackson serializes the transient member is because the getters are used to determine what to serialize, not the member itself - and since y has a public getter, that gets serialized. If you want to change that default and have Jackson use fields - simply do:

om.setVisibilityChecker(
  om.getSerializationConfig()
    .getDefaultVisibilityChecker()
    .withFieldVisibility(JsonAutoDetect.Visibility.ANY)
    .withGetterVisibility(JsonAutoDetect.Visibility.NONE)
);

Another way to ignore a property on serialization is to do it directly on the class:

@JsonIgnoreProperties(value = { "y" })
public class TestElement {
...

And another way is directly on the field:

public class TestElement {

    @JsonIgnore
    private String y;
...

Hope this helps.

edited Jan 14 '21 at 09:49

Nicolas Filotto

43,537
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answered Feb 13 '14 at 09:22

Eugen

8,523
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5

As I mentioned in the question, I'd prefer a way in which I don't have to tie my model to jackson specific annotations. One thing i can't understand is why jackson is serializing even transient member? Other API's like Smart JSON or even java serializer don't do that. Any idea about this? – Naman Feb 13 '14 at 17:03
3

I updated my original answer to explain the problem further and provide you with a solution - hope it helps. – Eugen Feb 13 '14 at 21:02
Thanks, i was looking for first solution. Now I can do this without having to use all the jackson specific annotations. – Naman Feb 14 '14 at 09:41
No worries - there are actually a few additional ways of doing this - you can check out my post on ignoring certain fields here: http://www.baeldung.com/jackson-ignore-properties-on-serialization - glad I could help. Cheers. – Eugen Feb 14 '14 at 11:21
3

Here's an alternative way (suggested as an edit) to do it: ```om.disable(MapperFeature.AUTO_DETECT_GETTERS) om.disable(MapperFeature.AUTO_DETECT_IS_GETTERS) om.enable(MapperFeature.AUTO_DETECT_FIELDS)``` – Eugen May 13 '15 at 10:08
1

So if I didn't miss something here, there's no way to get it to simply respect the transient keyword? (Which you'd imagine it would do automatically.) Yeah that sounds incredibly dumb. – Manius Jan 29 '20 at 19:30
Wouldn't this break compatibility with existing code using the getters and setters? – Eaton Emmerich Aug 22 '22 at 09:00

score 47 · Answer 2 · answered Aug 15 '16 at 13:30

47

A new way to stop Jackson from serializing and deserializing is to call mapper.configure(MapperFeature.PROPAGATE_TRANSIENT_MARKER, true).

answered Aug 15 '16 at 13:30

manuel

627
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7

This is confirmed to work with Kotlin's @Transient annotation on Kotlin version 1.2.71. – bartonstanley Oct 24 '18 at 19:56
This method is deprecated now - use: `JsonMapper.builder().configure(MapperFeature.PROPAGATE_TRANSIENT_MARKER, true)` – bbnt May 13 '23 at 15:19

score 9 · Answer 3 · answered Apr 30 '20 at 16:55

9

You can configure it with springs properties

spring.jackson.mapper.propagate-transient-marker=true

answered Apr 30 '20 at 16:55

Carlos Cuesta

1,262
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20

score 4 · Answer 4 · edited May 05 '16 at 12:33

I can't make comments so complete the previous response here, changing the (now) deprecated method setVisibilityChecker and adding a missing clause for booleans:

mapper.setVisibility(
    mapper.getSerializationConfig().
    getDefaultVisibilityChecker().
    withFieldVisibility(JsonAutoDetect.Visibility.ANY).
    withGetterVisibility(JsonAutoDetect.Visibility.NONE).
    withIsGetterVisibility(JsonAutoDetect.Visibility.NONE)
);

Why jackson is serializing transient member also?

4 Answers4

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