CODEWITHSUNDEEP
javajsonjackson
Michal Foksa
Michal Foksa

Reputation: 12024

Jackson ObjectMapper: How to omit (ignore) fields of certain type from serialization?

How can I tell Jackson ObjectMapper to ignore fields of certain type (class), in my case of Object.class, from serialization?

Constrains:

To help, below is a unit test expecting fields objectsList and objectField to be ignored from serialization, but its approach is not correct, it is filtering them by name instead of by their type.

public static class FavoriteShows {
    public Simpsons favorite = new Simpsons();
    public BigBangTheory preferred = new BigBangTheory();
}

public static class Simpsons {
    public String title = "The Simpsons";

    public List<Object> objectsList = List.of("homer", "simpson");
    public Object objectField = new HashMap() {{
        put("mr", "burns");
        put("ned", "flanders");
    }};
}

public static class BigBangTheory {
    public String title = "The Big Bang Theory";

    public List<Object> objectsList = List.of("sheldon", "cooper");
    public Object objectField = new HashMap() {{
        put("leonard", "hofstadter");
        put("Raj", "koothrappali");
    }};
}

public abstract static class MyMixIn {
    @JsonIgnore
    private Object objectField;
    @JsonIgnore
    private Object objectsList;
}

@Test
public void test() throws JsonProcessingException {
    // GIVEN
    // Right solution must work for any (MixIn(s) is out of questions) Jackson annotated class
    // without its modification.
    final ObjectMapper mapper = new ObjectMapper()
            .addMixIn(Simpsons.class, MyMixIn.class)
            .addMixIn(BigBangTheory.class, MyMixIn.class);

    // WHEN
    String actual = mapper.writeValueAsString(new FavoriteShows());
    System.out.println(actual);

    // THEN
    // Expected: {"favorite":{"title":"The Simpsons"},"preferred":{"title":"The Big Bang Theory"}}
    assertThat(actual).isEqualTo("{\"favorite\":{\"title\":\"The Simpsons\"},\"preferred\":{\"title\":\"The Big Bang Theory\"}}");

}

Upvotes: 1

Views: 3441

Answers (2)

Oleg Cherednik
Oleg Cherednik

Reputation: 18245

One of the way is to use custom AnnotationIntrospector.

class A {

    int three = 3;
    int four = 4;
    B b = new B();

    // setters + getters
}

class B {

    int one = 1;
    int two = 2;

    // setters + getters
}

To ignore all fields with type B:

ObjectMapper mapper = new ObjectMapper();
mapper.setAnnotationIntrospector(new JacksonAnnotationIntrospector() {
    @Override
    protected boolean _isIgnorable(Annotated a) {
        return super._isIgnorable(a)
                 // Ignore B.class
                 || a.getRawType() == B.class
                 // Ignore List<B>
                 || a.getType() == TypeFactory.defaultInstance()
                       .constructCollectionLikeType(List.class, B.class);
    }
});

String json = mapper.writeValueAsString(new A());

Upvotes: 3

Deadron
Deadron

Reputation: 5289

If you are using mixins you should be able to annotate with @JsonIgnoreType to have it ignore the class. docs For reference Globally ignore class in Jackson

Upvotes: 2

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