Jackson Backward Compatibility while changing Array type to Object

gistfile1.txt

// New Model

class Person {
    private int id;

    @JsonDeserialize(using = CustomDeserializer.class)
    @JsonAlias("addresses")
    private AddressDetails addressDetails;

    public Person() {

    }

    public Person(int id, AddressDetails addressDetails) {
        this.id = id;
        this.addressDetails = addressDetails;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public AddressDetails getAddressDetails() {
        return addressDetails;
    }

    public void setAddressDetails(AddressDetails addressDetails) {
        this.addressDetails = addressDetails;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", addressDetails=" + addressDetails +
                '}';
    }
}

class CustomDeserializer extends JsonDeserializer<AddressDetails> {

    @Override
    public AddressDetails deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
        JsonNode jsonNode = jsonParser.getCodec().readTree(jsonParser);
        if (jsonNode.isArray()) {
            AddressDetails addressDetails = new AddressDetails();
            List<AddressInfo> addressInfos = new ArrayList<>();
            for (JsonNode next : jsonNode) {
                AddressInfo addressInfo = getAddressInfo(next);
                addressInfos.add(addressInfo);
            }
            addressDetails.setAddressInfos(addressInfos);
            return addressDetails;
        } else {
            return jsonParser.getCodec().treeToValue(jsonNode, AddressDetails.class);
        }
    }

    private AddressInfo getAddressInfo(JsonNode next) {
        String addressLine1 = next.get("addressLine1").asText();
        String city = next.get("city").asText();
        String country = next.get("country").asText();
        return new AddressInfo(addressLine1, city, country);
    }
}

class AddressDetails {
    private List<AddressInfo> addressInfos;

    public AddressDetails() {

    }

    public List<AddressInfo> getAddressInfos() {
        return addressInfos;
    }

    public void setAddressInfos(List<AddressInfo> addressInfos) {
        this.addressInfos = addressInfos;
    }

    public AddressDetails(List<AddressInfo> addressInfos) {
        this.addressInfos = addressInfos;
    }

    @Override
    public String toString() {
        return "AddressDetails{" +
                "addressInfos=" + addressInfos +
                '}';
    }
}

class AddressInfo {
    private String addressLine1;
    private String city;
    private String country;

    public AddressInfo() {

    }

    public AddressInfo(String addressLine1, String city, String country) {
        this.addressLine1 = addressLine1;
        this.city = city;
        this.country = country;
    }

    public String getAddressLine1() {
        return addressLine1;
    }

    public String getCity() {
        return city;
    }

    public String getCountry() {
        return country;
    }

    public void setAddressLine1(String addressLine1) {
        this.addressLine1 = addressLine1;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    @Override
    public String toString() {
        return "AddressInfo{" +
                "addressLine1='" + addressLine1 + '\'' +
                ", city='" + city + '\'' +
                ", country='" + country + '\'' +
                '}';
    }
}

gistfile2.txt

// Old Model

class Person {
    private int id;

    private List<Address> addresses;

    public Person() {

    }

    public Person(int id, List<Address> addresses) {
        this.id = id;
        this.addresses = addresses;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public List<Address> getAddresses() {
        return addresses;
    }

    public void setAddressDetails(List<Address> addresses) {
        this.addresses = addresses;
    }
}

class Address {
    private String addressLine1;
    private String city;
    private String country;

    public Address() {

    }

    public Address(String addressLine1, String city, String country) {
        this.addressLine1 = addressLine1;
        this.city = city;
        this.country = country;
    }

    public String getAddressLine1() {
        return addressLine1;
    }

    public String getCity() {
        return city;
    }

    public String getCountry() {
        return country;
    }

    public void setAddressLine1(String addressLine1) {
        this.addressLine1 = addressLine1;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public void setCountry(String country) {
        this.country = country;
    }
}

Jackson Deserialization

// Below two string are created using two different models: Refer below two files to track the changes between models

        String oldString = "{\"id\":1,\"addresses\":[{\"addressLine1\":\"Central Park\",\"city\":\"NYC\",\"country\":\"UK\"},{\"addressLine1\":\"Near Wembley\",\"city\":\"London\",\"country\":\"UK\"}]}";
        String newString = "{\"id\":1,\"addressDetails\":{\"addressInfos\":[{\"addressLine1\":\"Central Park\",\"city\":\"London\",\"country\":\"UK\"},{\"addressLine1\":\"Near Wembley\",\"city\":\"London\",\"country\":\"UK\"}]}}";
        ObjectMapper objectMapper = new ObjectMapper();
        try {
            Person person1 = objectMapper.readValue(oldString, Person.class);
            Person person2 = objectMapper.readValue(newString, Person.class);
            System.out.println(person1);
            System.out.println(person2);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }