jackson ignore default value when it's true

Elie Roux :

I'm having a class that has a default value which is true and I want to ignore the default in serialization. It works when the default is false, but not when the default is true:

    public static final class TestBooleanDefaultTrue {
        @JsonInclude(Include.NON_DEFAULT)
        @JsonProperty(value="display")
        public Boolean display = Boolean.TRUE;
        public String s = "test";

        public TestBooleanDefaultTrue() {}
    }

    public static final class TestBooleanDefaultFalse {
        @JsonInclude(Include.NON_DEFAULT)
        @JsonProperty(value="display")
        public Boolean display = Boolean.FALSE;
        public String s = "test";

        public TestBooleanDefaultFalse() {}
    }

    @Test
    public void readBVMTest() throws JsonGenerationException, JsonMappingException, IOException {
        testom.writeValue(System.out, new TestBooleanDefaultTrue());
        testom.writeValue(System.out, new TestBooleanDefaultFalse());
    }

which outputs (after cheating a bit):

{"s":"test","display":true}
{"s":"test"}

How can I ignore the default value when it is true?

sfiss :

You can use a custom filter, because the NON_DEFAULT does not consider what you assign, but the default value of the wrapper type.

 public static final class MyFilter {

    @Override
    public boolean equals(final Object obj) {
        if (obj == null || !(obj instanceof Boolean)) {
            return false;
        }
        // date should be in the past
        final Boolean v = (Boolean) obj;
        return Boolean.TRUE.equals(v);
    }
}

public static final class TestBooleanDefaultTrue {

    @JsonInclude(value = Include.CUSTOM, valueFilter = MyFilter.class)
    @JsonProperty(value = "display")
    public Boolean display = Boolean.TRUE;
    public String s = "test";

    public TestBooleanDefaultTrue() {
    }
}



public static final class TestBooleanDefaultFalse {

    @JsonInclude(Include.NON_DEFAULT)
    @JsonProperty(value = "display")
    public Boolean display = Boolean.FALSE;
    public String s = "test";

    public TestBooleanDefaultFalse() {
    }
}

@Test
public void readBVMTest() throws JsonGenerationException, JsonMappingException, IOException {
    assertEquals(getOM().writeValueAsString(new TestBooleanDefaultTrue()), "{\"s\":\"test\"}");
    assertEquals(getOM().writeValueAsString(new TestBooleanDefaultFalse()), "{\"s\":\"test\"}");

}

EDIT for completeness from the javadoc of JsonInclude.Include.NON_DEFAULT, emphasis mine:

When NOT used for a POJO (that is, as a global default, or as property override), definition is such that: All values considered "empty" (as per NON_EMPTY) are excluded, Primitive/wrapper default values are excluded, Date/time values that have timestamp (long value of milliseconds since epoch, see Date) of 0L are excluded