There is no possibility to set jsonNodeFactory when working with patches.

[gabrielsson]

I would like to use the library withExactBigDecimals, i.e keeping 25.000 when patching a node.

@Test
void testDecimalsKeptAfterPatch() {

    ObjectMapper mapper = new ObjectMapper()
        .enable(DeserializationFeature.USE_BIG_DECIMAL_FOR_FLOATS)
        .setNodeFactory(JsonNodeFactory.withExactBigDecimals(true));

    JsonNode newer = mapper.readTree("25.000");
    JsonNode older = mapper.readTree("24.444");
    JsonNode apply = JsonMergePatch.fromJson(newer).apply(older);

    assertEquals("25.000", apply.asText());
}

org.junit.ComparisonFailure: expected:<25[.000]> but was:<25[]>
Expected :25.000
Actual   :25

Is it possible to inject the behaviour I am after?
The JacksonUtils that JsonMergePatch is using sets the factory to JsonNodeFactory.instance and I cannot see a way around this. I would prefer to use the JsonNodeFactory.decimalsAsIs for my specific case.

This also applies to the JsonDiff.asJson(older, newer) with the same behaviour as the above example.

[MCakrt]

I've just come across this problem, too :(
Let me know if you find a solution.

[gabrielsson]

No unfortunately not. I changed my schemas to string instead of number.
However I did successfully make a version without JacksonUtils but it did not feel like the correct solution.

[MCakrt]

Hm... in my case I serialize and deserialize some classes with BigDecimal fields using objectmapper. I never had any problems with that, no loss of trailing zeroes.

I only encountered the problem when converting the object to JsonNode (to be used with JsonPatch)

JsonNode node = objectMapper.convertValue(someObjectWithBigDecimalField, JsonNode.class);

Then the trailing zeroes were trimmed.

But in this case, I just added .setNodeFactory(JsonNodeFactory.withExactBigDecimals(true) and everything works as expected.

So my problem is different from yours. My problems was that BigDecimals got trimmed while you have problem with string->BigDecimal deserialization.