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Cannot read Optionals written with StdTypeResolverBuilder #86
Description
The following test fails on Jackson 2.9.7 and passes on 2.8.11:
@Test
public void test() throws Exception {
ObjectMapper mapper = new ObjectMapper();
mapper.setDefaultTyping(
new StdTypeResolverBuilder()
.init(JsonTypeInfo.Id.CLASS, null)
.inclusion(JsonTypeInfo.As.WRAPPER_OBJECT)
);
mapper.registerModule(new Jdk8Module());
String json = mapper.writeValueAsString(new Foo(Optional.of(1)));
System.out.println(json);
mapper.readValue(json, Foo.class);
}
public static class Foo {
private Optional<Integer> bar;
public Foo() {
}
public Foo(Optional<Integer> bar) {
this.bar = bar;
}
public Optional<Integer> getBar() {
return bar;
}
public void setBar(Optional<Integer> bar) {
this.bar = bar;
}
}
Complete runnable project with this test-case can be found on https://github.com/isopov/jackson-optional-test
Activity
[-]Cannot read read written Optionals with StdTypeResolverBuilder [/-][+]Cannot read Optionals written with StdTypeResolverBuilder [/+]isopov commentedon Oct 24, 2018
Added workaround, involving copy&pasting classes from 2.8.11 - https://github.com/isopov/jackson-optional-test/blob/workaround/src/test/java/com/example/OptionalJacksonTest.java
Still proper fix will be highly appreciated.
cowtowncoder commentedon Oct 30, 2018
I will have to say that it is quite possible that combination of polymorphic type in
Optionalfor root value may be unsupportable. I would strongly recommend not using that combination: partly since root values have significant challenges wrt type erasure, and partly asOptionals are challenging in their own right.In fact I am considering adding a warning that polymorphic type handling is not recommended to be used for root values at all.
Having said that: I will try to figure out if this can be made to work correctly (although depending on changes they might only be made to 2.9 branch), and I hope this is the case.
Thank you for reporting the problem.
EDIT: Looking at this further,
Optionalis NOT used as root value. So that's not the problem.cowtowncoder commentedon Aug 19, 2019
To help future work, output looks like:
and that would seem to be missing type information for contents, somehow.
cowtowncoder commentedon Dec 7, 2024
@JooHyukKim this might be worth looking into as well.
JooHyukKim commentedon Dec 7, 2024
Ah so this is how we want the output object is in 2.8.
{ "com.fasterxml.jackson.datatype.jdk8.OptionalStdTypeResolverBuilder86Test$Foo": { "bar": { "java.util.Optional": 1 } } }If we try to read above JSON output from 2.8, in later version, throws error saying...
cowtowncoder commentedon Dec 7, 2024
Hmmmh. Now that I think about this, there's a problem... Although we do need the type id of the contained value, we also need to know there's
Optionalin-between.So not 100% sure what type id is needed. It's almost as if we needed
Optional<Integer>.To further complicate things tho,
Integeris so-called "natural" type, for which no type id is to be output. Ugh.I also realized that the test case is incomplete; it doesn't seem to verify actual contents.