【Question】

This is how my JSON looks like:

 

{

 “data” :

[

{ “f1” : “v1”,

“f2” : “v2”,

“group” : [

{ “f3” : “x1”,

        “f4” : “y1”,

        “f5” : “z1”

},

{ “f3” : “x1”,

      “f4” : “y2”,

        “f5” : “z2”

},

{ “f3” : “x2”,

    “f4” : “y3”,

        “f5” : “z3”

}]

},

{ “f1” : “vf1”,

    “f2” : “vf2”,

    “group” : [

{ “f3” : “x1”,

“f4” : “y1”,

        “f5” : “z1”

},

{ “f3” : “x1”,

“f4” : “y2”,

        “f5” : “z2”

},

{ “f3” : “x1”,

  “f4” : “y3”,

        “f5” : “z3”

}]

}

]

}

 

I am using the following code to convert it into CSV:

JSONArray array = (JSONArray)json.get(“data”);

String dataCSV = CDL.toString(array);

But this code is giving me “null” in dataCSV.

I want to know why it is getting null in dataCSV and also please provide a solution on “How to get CSV from this JSON ?” or “from a POJO Class to CSV”.

Thanks in advance.

 

【Answer】

f1 and f2 are the first level (which is equivalent to a grouping expression). They need to union with its next level of data (which is equivalent to detailed data in each group). The process is converting multilevel JSON data to a single level data (2D table) to be output to a CSV. It’s simple to do this in SPL (Structured Process Language):

	A
1	=file(“d:\\data.json”).read()
2	=json(A1).dat
3	=A2.news(group;A2.f1,A2.f2,f3,f4,f5)
4	=file(“d:\\result.csv”).export@c(A3)

A3’s result:

 

A1: Read in the JSON data.

A2: Parse JSON data to get the nodes.

A3: Get needed fields to generate a new sequence.

A4: Write data under the fields to a CSV file.

The SPL code can be easily integrated into a Java application. See How to Call an SPL Script in Java.