mapping rest responses with Jackson JSON

问题

I have a REST call that can return either AccountPojo or ErrorCodePojo. Each of these have specific fields. How can I use the Jackson JSON libary to easily parse the response and fetch AccountPojo or the ErrorCodePojo?

I have something like:

ObjectMapper mapper = new ObjectMapper();
try {
   ret = mapper.readValue(json, AccountPojo.class);
} catch (JsonProcessingException e) {
   ret = mapper.readValue(json, ErrorCodePojo.class);
}

but I don't think this is nice.

Thanks!

回答1:

You can also use ObjectMapper#convertValue method. With this method your parsing algorithm could look like this:

1. Deserialize JSON to Map class.
2. Check if map contains property from class AccountPojo/ErrorCodePojo.
3. Convert map to the target class.

For example, let's assume that your ErrorCodePojo class looks like this:

class ErrorCodePojo {

    private int errroCode;
    private String message;

    //getters, setters
}

Property errroCode exists only in ErrorCodePojo. AccountPojo does not contain this property.

// Step 1
Map<?, ?> value = mapper.readValue(json, Map.class);
// Step 2
if (value.containsKey("errroCode")) {
    // Step 3
    mapper.convertValue(value, ErrorCodePojo.class);
} else {
    // Step 3
    mapper.convertValue(value, AccountPojo.class);
}

来源：https://stackoverflow.com/questions/21004643/mapping-rest-responses-with-jackson-json