Is it possible to perform validation at parser level?

[Dragas]

suppose i have following pojo that i do (de)serialization operations with

class Foo {
    private List<String> bar;
    public Foo(@JsonProperty("bar") List<String> bar) {
        this.bar = bar;
    }
    public List<String> getBar() {
        return bar;
    }
}

and it maps to following json structure

{
  "bar": ["foo", "bla", "la"]
}

is it possible to define at deserialization level that I expected N elements at most for property bar
when deserializing given structure as object of type Foo? Expectation is something similar to
that of XML schemas, where schema defines how many times a given tag can appear ala

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="unqualified" targetNamespace="scratch_83.xsd"
        xmlns:scr="scratch_83.xsd"
> 
    <xs:element name="foo">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="scr:bar" minOccurs="0" maxOccurs="5"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="bar">
        <xs:simpleType>
            <xs:restriction base="xs:string"/>
        </xs:simpleType>
    </xs:element>
</xs:schema>

in this example i configured the element bar to appear 5 times using maxOccurs attribute, but given that json schemas
aren't that widely adopted i'm looking for equivalent way to pass information via the parser

expectation is to prevent accidental ddos by passing oversized collections and tricking the application into doing a lot
of busy work for no reason.

i do see there is StreamReadConstraints in jackson-core which limits the json document size to 20mb by default which is
great, and the respective request which requested to increase default to 1gb in jackson-core#1082 (why??)

i looked through annotations in jackson-core, and jackson-annotation but none of them seem to suffice. closest seems to be
@JsonFilter, but it seems to only prevent serialization of given field

[cowtowncoder]

No, Jackson explicitly stays out of content validation business: expectation is that validation is done separately using something like Bean Validation API or such. Hence there are no validation annotations, nor plans to add any (or support).

You could/need to add validation logic in your POJOs, and/or use validation frameworks.