Parse complex string in spark streaming

Question

I am getting a stream data set from Azure event hubs. The data is coming in the following format:

[
  [
    {
      "data": "sampledata1",
      "addressdata": {
        "isTest": false,
        "address": "washington",
        "zipcode": 98119,
        "city": "seattle",
        "randomstring": "abcdabcd:ghkjnkasd:asdasdasd"
      },
      "profession": "engineer",
      "party": "democrat"
    },
    {
      "data": "sampledata2",
      "addressdata": {
        "isTest": false,
        "address": "virginia",
        "zipcode": 20120,
        "city": "Centreville",
        "randomstring": "zabcdabcd:tghkjnkasd:gasdasdasd"
      },
      "profession": "teacher",
      "party": "republican"
    }
  ]
]

From the following article, I can get the json as raw string. https://docs.databricks.com/spark/latest/structured-streaming/streaming-event-hubs.html

But I cannot extract individual item from the string using get_jon_object. I believe the problem is that the string is not a single json object, it is an array of array of json. So, the get_json_object is not able to parse it.

val outputDf = streamingInputDf.select(
     get_json_object(($"body").cast("string"), "$.data").alias("data"), 
     get_json_object(($"body").cast("string"), "$.addressdata").alias("addressdata"), 
     get_json_object(($"body").cast("string"), "$.profession").alias("profession"), 
     get_json_object(($"body").cast("string"), "$.party").alias("party"), 
     date_format($"enqueuedTime", "dd.MM.yyyy").alias("day"),
     date_format($"enqueuedTime", "HH").cast("int").alias("hour") ,
     when(date_format($"enqueuedTime", "mm").cast("int")<=15,1)
    .when(date_format($"enqueuedTime", "mm").cast("int")>15 && date_format($"enqueuedTime", "mm").cast("int")<=30,2)
    .when(date_format($"enqueuedTime", "mm").cast("int")>30 && date_format($"enqueuedTime", "mm").cast("int")<=45,3)
    .otherwise(4).alias("minute")
)

Anyone have any suggestion, how to gracefully parse the data and extract individual information from the string? Any method similar to get_json_object that can extract data from array of json?

PS: I get the array of json in one line. not like mentioned above.

Why not `from_json` - [How to query JSON data column using Spark DataFrames?](https://stackoverflow.com/q/34069282/10465355) and [How to read records in JSON format from Kafka using Structured Streaming?](https://stackoverflow.com/q/43297973/10465355) — 10465355, Nov 07 '18 at 09:57

score 0 · Answer 1 · answered Nov 07 '18 at 05:00

To work with Json type format, there is a bunch of tools to use in java. But In my experience in different platforms, Google Gson is really the best according to different aspects like performance and accuracy. (Gson library: https://github.com/google/gson)

Additionally, It's really so easy to use like below sample code:

String json = {"insurance1":45.1,"insurance2":505.5};
Gson gson = new Gson();
Map<String, Float> jsonObj = gson.fromJson(json, Map.class);
System.out.println(jsonObj.get("insurance1"));

Moreover, If there is a need to have a much more complex and custom data structures you can create an Entity and use that in fromJson method instead of Map class in above example. And as your sample Json, if there an array or list of these complex objects, you can use TypeToken to define the input Json structure and use this in fromJson method like below sample format:

new TypeToken<ArrayList<Class.forName(MyClass)>>

for more information about TypeToken, you can use this link: TypeToken

Parse complex string in spark streaming

1 Answers1