Gson / Retrofit解析变量JSON

Question

I'm struggling in parsing a JSON Object with variable content to a Java Object.

Normally, I'd try to map a JSON Object to a POJO, however in this case I don't know what to do.

My JSON looks like this:

"parts": [
           [
             "text",
             "http://www.example.com/"
           ],
           [
             "page",
             [
               "http://www.example.com/",
               "\n\t\n\t\t\n\t\t\tSome of the Page Content preview here...",
               "",
               "/path/to/picture.jpg"
             ]
           ],
           [
             "text",
             "Another String here "
           ]
         ]

Running this piece of code trough a typical Json to Java Object converter doesn't work because this cannot be mapped to a simple POJO.

I tried converting to List<List<String>>> myObject; but as expected this gives me an exception:

W: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected a string but was BEGIN_ARRAY at line 1 column 9563 path $[3]./object.parts[1][1]

I think I'll have to create a custom DeSerializer for this, however I have no idea where to start.

Any help pointing me in the good direction would be greatly appreciated.

EDIT: As pointed out in the comments, is the JSON data supplied not in valid key-value pair formation. I've contacted the API providers and they will sort this out.

Until I come across a way of dealing with this problem on the frontend, I'll keep this question open.

Answer 1

So after looking at this problem again after af few days, I've finally found a solution that works for my case!

In stead of trying to parse the element into a String as in my first attempts. I'm now storing the data to a simple java.lang.Object

My model now looks like this:

@SerializedName("parts")
@Expose
private List<List<Object>> parts = new ArrayList<List<Object>>();

This prevents the GSON parsing process from crashing the app when the invalid array is detected.

When trying to access the data, I now check if the Object is of type String , if this is the case I continue, ignoring all Arrays.

In my code this looks like this: (In my case, I only need the text attribute of the first element in the parts array)

 List<List<Object>> partList = myParsedObject.getParts();
    if (partList.size() > 0) {
        if (partList.get(0).size() > 1) {
            if (partList.get(0).get(1) instanceof String) {
                return partList.get(0).get(1).toString();
            }
        }
    }

Answer 2

The second element in the second array element is also an array in the JSON that you posted.

Since GSON is expecting a list of lists of Strings, it fails to parse the document beginning at this point.

"parts": [
       ...,
       [
         "page",
         [  <--- Problematic array begin
           "http://www.example.com/",
           "\n\t\n\t\t\n\t\t\tSome of the Page Content preview here...",
           "",
           "/path/to/picture.jpg"
         ]
       ],
       ...
     ]

Answer 3

Your JSON is not well formatted, I tried checking your posted JSON onto an Online JSON Formatter and it cannot parse your JSON. You need to encapsulate that JSON inside curly braces, like this :

{"parts": [
       [
         "text",
         "http://www.example.com/"
       ],
       [
         "page",
         [
           "http://www.example.com/",
           "\n\t\n\t\t\n\t\t\tSome of the Page Content preview here...",
           "",
           "/path/to/picture.jpg"
         ]
       ],
       [
         "text",
         "Another String here "
       ]
     ]
}

That JSON will be successfully parsed by the Online JSON Formatter, and you should be able to parse it just fine. The problem is you have to work on lots of JSON Array which does not have any key to identify them. Mapping it would be troublesome because of the JSON Array after the "page" string.

If my suggested JSON can be mapped into a List<List<String>> POJO, you'll have to get the second element and manually parse it again, since the second array still have an array inside it.

Hope this helps and good luck!!!

Regards,

Reid