Polymorphism deserialization

[Mattia Amato]

Hi

I have a problem with polymorphism and deserialization.

Here the situation: I have an abstract Message class:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")

@JsonSubTypes({ @JsonSubTypes.Type(value = MacAddrRequest.class, name = "MacAddrRequest") })

public abstract class Message {

private String messageId;

public Message(String messageId) {

setMessageId(messageId);

}

public String getMessageId() {

return messageId;

}

public void setMessageId(String messageId) {

this.messageId = messageId;

}

}

which is extended by the MacAddrRequest class:

@JsonTypeName(value = "MacAddrRequest")

public class MacAddrRequest extends Message {

public MacAddrRequest(String messageId) {

super(messageId);

}

}

I serialize the MacAddrRequest class like this:

private ObjectMapper mapper = new ObjectMapper();
mapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
String m1 = mapper.writeValueAsString(new MacAddrRequest(UUID.randomUUID().toString()));

The question is: How do I deserialize the Message class ?

private ObjectMapper objectMapper = new ObjectMapper();
Message m = objectMapper.readValue(request, Message.class);

    if (m instanceof MacAddrRequest){
        response = "Ok";
    }

Thanks for the help

[Tatu Saloranta]

The code should work as you suggested, since Message is marked as polymorphic, and has @JsonSubTypes to point to known implementing classes.

Are you having an issue with this?

-+ Tatu +-

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[Mattia Amato]

I found the problem!

To let the whole thing work I needed to add:

@JsonProperty("messageId")

for each argument in the different constructors. 

I created a Packet class that stores the abstract Message (a "container" for the message).

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, visible = true, property = "@class")

public class Packet {

private Message message;

public Packet(@JsonProperty("message") Message message) {

setMessage(message);

}

public Message getMessage() {

return message;

}

public void setMessage(Message message) {

this.message = message;

}

}

Since the class Message is abstract I think that this is the only possible solution.
To deserialize it I did the following:

private ObjectMapper objectMapper = new ObjectMapper();

Packet p = objectMapper.readValue(request, Packet.class);

    if (p.getMessage() instanceof MacAddrRequest){
        response = "Ok";
    }

- Mattia