On Mon, Jun 8, 2020 at 9:33 AM charles chung <[email protected]>
wrote:
> If in json string, the property is missing, and the corresponding Java
> type is Optional, the deserialized field value is null, where
> Optional.Empty is expected.
>
>
Yes, this is how Jackson works. Properties that are encountered are
processed, and that is it.
Expectation is that if you want "default values", your POJO will assign
them in declaration or constructor.
There is no attempt to check what might exist, with one exception: if you
specify Creator method (constructor or static factory method annotated with
`@JsonCreator`), then properties passed through it will have to be
initialized somehow.
So if you want to force setting of `Optional` property with
`Optional.empty()`, you should either make that assignment yourself by
default (in field declaration or default constructor) OR use
`@JsonCreator`. Latter has the benefit that you can also use
`@JsonProperty(required = true)` to throw exception if the value is not
included in json.
I hope this helps,
-+ Tatu +-
> There is the code to reproduce this issue.
>
> // I know that using Optional type in class field is generally regarded as
> an anti-pattern.
>
>
> public static class FooRequest {
> private Optional<Long> foo;
>
> public Optional<Long> getFoo() {
> return foo;
> }
>
> public void setFoo(Optional<Long> foo) {
> this.foo = foo;
> }
> }
>
>
> @Test
> public void testDeserializeOptional_property_missing() throws
> Exception {
> ObjectMapper mapper = new ObjectMapper();
> mapper.registerModule(new Jdk8Module());
> FooRequest fooRequest = mapper.readValue("{}", FooRequest.class);
> * // the issue : fooRequest.foo is null here, where Optional.Empty
> is expected*
> Assert.assertFalse(fooRequest.getFoo().isPresent());
> }
>
> @Test
> public void testDeserializeOptional_property_isnull() throws Exception
> {
> ObjectMapper mapper = new ObjectMapper();
> mapper.registerModule(new Jdk8Module());
> FooRequest fooRequest = mapper.readValue("{\"foo\":null}",
> FooRequest.class);
> Assert.assertFalse(fooRequest.getFoo().isPresent());
> }
>
> --
> You received this message because you are subscribed to the Google Groups
> "jackson-user" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to [email protected].
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/jackson-user/97734ab4-cebf-4646-a90d-aaf45960a2dao%40googlegroups.com
> <https://groups.google.com/d/msgid/jackson-user/97734ab4-cebf-4646-a90d-aaf45960a2dao%40googlegroups.com?utm_medium=email&utm_source=footer>
> .
>
--
You received this message because you are subscribed to the Google Groups
"jackson-user" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/jackson-user/CAGrxA26tivoQKCET93MHYBhisrSJFTjxGiTS%2BFDTnp3V6%2BPbrg%40mail.gmail.com.
