GSON我可以只转换JSON的一部分吗，我想使用GSON.fromJSON（）

Question

I am working with a big JSON object which has responses form multiple requests.

And the part I am working on requires only few object and they are not always in front. For Example the json structure is:

**

json = {
    mainDocument: {
        element1: {
            element11: "value11",
            element12: {
                element121: "value121"
                }
            },
        element2: {
            element21: {
                element211: {
                    element2111: "value2111",
                    element2112: {
                        element21121: "value21121"
                        }
                    }
                },
            element22: "value22"
            }
        }
    }

**

This structure can change depending on whether or not the request is successful.

Now, I want to create an java object with the value of element11, element 22, element21121.

Currently I just check the json and use the setters of the object.

I want to know if there is a way to let GSON handle this and not have to parse the json myself.

Thanks in advance for any help you can offer.

Answer 1

I don't know if I understand your question very well, but in order to deserialize a JSON response with Gson, the most proper way in my opinion is to create a class structure that encapsulates the data in the response. In your case something like:

class Response
  MainDocument mainDocument

class MainDocument
  Element element1
  Element element2

class Element
  ...

If you only need some data from the JSON, you can omit attributes in your class structure and Gson will ignore them. And if an object can have different contents in different responses, you can have something like this:

class Response
  MainDocument mainDocument
  Error error

And Gson will parse responses both with a root element mainDocument (like the one in the question) or with a root element error ... this allows you to adapt your parsing to variable responses...

Obviously, to follow this approach, you need to know all the possible response structures you can have. If your problem is that your JSON response is absolutely variable, and you cannot create a class struture to wrap it, you always could do a manual parsing, somehting like this:

JsonParser parser = new JsonParser();
JsonObject rootObj = parser.parse(jsonString).getAsJsonObject();    
String element21121 = rootObj
                       .getAsJsonObject("mainDocument")
                       .getAsJsonObject("element2")
                       .getAsJsonObject("element21")
                       .getAsJsonObject("element211")
                       .getAsJsonObject("element2112")
                       .getAsString("element21121");