将值注入Jackson转换器/解串器

Question

I'm porting a legacy API to Java from a Ruby app that takes full advantage of not being statically typed.

In one such situation, the API accepts from the JSON body a user_id that is either a numeric user ID or the string "me" , (which should be converted to the ID of the user making the request before being saved to the database). The method looks like this:

@PUT
@Path("{key}")
@UnitOfWork
public Response getMyObjByKey(@PathParam("key") String key, MyObj myObj) {
    myObjDAO.save(myObj);
}

I have a converter that I want to look something like this:

public class UserIdConverter extends StdConverter<String, Integer> {

    @Inject
    @AuthUser
    protected AuthenticatedUser user;

    public Integer convert(String strUserId) {
        // if strUserId is "me"
        return user.getId();
    }
}

Of course, this doesn't work because of...something to do with the lifecycle that causes user to be null .

My question is: Is there a way for me to access the user object in the converter?

Answer 1

To my knowledge its not possible to access the User during the deserialization. Try a custom deserializer and place an indicating int as the id if the String "me" is received. Something like:

public class MyObjDeserializer extends JsonDeserializer<MyObj>{

    @Override
    public MyObj deserialize(JsonParser jp, DeserializationContext dc) throws IOException, JsonProcessingException {

        ObjectCodec oc = jp.getCodec();
        JsonNode node = oc.readTree(jp);

        MyObj myobj = new MyObj();
        myobj.setName(node.get("name").textValue());
        // set other attributes...

        String idString = node.get("id").textValue();
        int id = -1;
        if(!idString.equals("me")) { 
           // another option: use idString.matches("-?\\d+") to check if its a number - https://stackoverflow.com/a/15801999/7015661
            id = Integer.parseInt(idString);
        }

        myobj.setId(id);

        return myobj;
    }

}

Then in your MyObj class place @JsonDeserialize(using = MyObjDeserializer.class) to use your own deserializer.

Now if the id is "-1", you can get the user's own id in the resource method as follows:

@PUT
@Path("{key}")
@UnitOfWork
public Response getMyObjByKey(@PathParam("key") String key, MyObj myObj, @Auth Optional<User> user) {

    if(myObj.getId() == -1){
        if(!user.isPresent) // something went very wrong
             throw new RuntimeException("User not authenticated");

       myObj.setId(user.get().getId()); // set the id to its correct value
    }

    myObjDAO.save(myObj);
}

Hope this works :)