我可以添加一个新字段以在服务器端进行响应，而旧客户端不会因杰克逊反序列化而中断吗？

Question

I have a class at server :

Class A{
int x;
int y;
// getters and setters
}

in old client

Class A{
int x;
}

in new client

Class A{
int x;
int y;
}

now i can't change the old client code and the client gives org.codehaus.jackson.map.exc.UnrecognizedPropertyException. i can change the server or new client code.

How can i make this work with jackson serializer?

Answer 1

Different format:

You can use Views on the server to decide during runtime which properties to include. The new client could then request the same content as old client, but with a different parameter/header or via different API path that simply uses a new view with new properties.

Same format:

If the old client doesn't support the new format, you cannot simply force it to support it without modifying the client. In fact, if you could do something like this, it would be quite dangerous, as it would imply existing applications could not rely on their format restrictions.

However, if you can modify old client, here's something you can do:

1. Add @JsonIgnoreProperties(ignoreUnknown = true) to the POJO in old client
2. If you can't modify POJO, but can access ObjectMapper: objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
3. If you can access ObjectMapper, but don't want to affect all other POJOs too, you can mix-in the annotation just for that one POJO