Xbasic

json_flatten Function

Syntax

C output = json_flatten(jsonIn as C, template as C)

Arguments

jsonInCharacter

The JSON data.

templateCharacter

A template that defines how to flatten the JSON data.

Description

The json_flatten function takes a JSON string that defines an array of hierarchical objects and 'flattens' the array.

Discussion

This function is useful for Reporting where the report data source is set to a Custom data source that returns JSON data. If the JSON data that is returned is hierarchical, then you will need to 'flatten' it in order to get it into an appropriate format for the report writer.

This function can only be used with JSON that contains data in the form of a parent-child relationship:

parent --> child --> grandchild

json_flatten() is not designed to handle parallel one-to-many relationships, such as the one shown below. To flatten JSON data that contains multiple one-to-many parent-child relationships, use the json_shred() function.

' json_flatten() does not support the following structure
' Use json_shred() instead

parent --> child1
       --> child2

Example: Flattening Order Data 

The format of the template for the json_flatten() function is shown in the following example. Consider the following JSON String:

[
    {
        "id": "alfki",
        "name": "customer 1",
        "__a5crc": -253329,
        "orders": [
            {
                "orderId": 1,
                "orderData": "12/1/2013",
                "ordcust": "1|||alfki",
                "orderDetails": [
                    {
                        "lineitemId": 1,
                        "prodId": 1,
                        "qty": 3,
                        "ordprod": "1|||1"
                    },
                    {
                        "lineitemId": 4,
                        "prodId": 3,
                        "qty": 2,
                        "ordprod": "1|||3"
                    }
                ]
            },
            {
                "orderId": 3,
                "orderData": "12/3/2013",
                "ordcust": "3|||alfki",
                "orderDetails": [
                    {
                        "lineitemId": 6,
                        "prodId": 4,
                        "qty": 9,
                        "ordprod": "3|||4"
                    },
                    {
                        "lineitemId": 7,
                        "prodId": 3,
                        "qty": 1,
                        "ordprod": "3|||3"
                    }
                ]
            }
        ]
    },
    {
        "id": "bolid",
        "name": "customer 2",
        "__a5crc": -194126,
        "orders": [
            {
                "orderId": 2,
                "orderData": "12/2/2013",
                "ordcust": "2|||bolid",
                "orderDetails": [
                    {
                        "lineitemId": 2,
                        "prodId": 6,
                        "qty": 6,
                        "ordprod": "2|||6"
                    },
                    {
                        "lineitemId": 3,
                        "prodId": 9,
                        "qty": 7,
                        "ordprod": "2|||9"
                    }
                ]
            }
        ]
    }
]

The JSON object defined by the above string shows an array of customers with embedded orders. For each order, there are embedded line-items.

The structure of the JSON object is

Customers,
        Orders,
            Order Details

The json_flatten() function takes two arguments - the JSON string you want to flatten, and a template that defines which properties in the input JSON you want to map to the output JSON.

Assume that the following template is specified:

{
    "id" : "id" ,
    "name" : "name" ,
    "orders" : [ 
        { 
            "orderId" : "orderId" , 
            "orderData" : "orderData" , 
            "orderDetails" : [
                { 
                    "lineitemId" : "lineitemId" , 
                    "prodId" : "prodId" , 
                    "qty" : "qty" 
                }
            ] 
        } 
    ]
}

If you 'flatten' this JSON using the above template, you will get the following output:

[  { "id" : "alfki" , "name" : "customer 1" , "orderId" : 1 , "orderData" : "12/1/2013" , "lineitemId" : 1 , "prodId" : 1 , "qty" : 3 }
 ,  { "id" : "alfki" , "name" : "customer 1" , "orderId" : 1 , "orderData" : "12/1/2013" , "lineitemId" : 4 , "prodId" : 3 , "qty" : 2 }
 ,  { "id" : "alfki" , "name" : "customer 1" , "orderId" : 3 , "orderData" : "12/3/2013" , "lineitemId" : 6 , "prodId" : 4 , "qty" : 9 }
 ,  { "id" : "alfki" , "name" : "customer 1" , "orderId" : 3 , "orderData" : "12/3/2013" , "lineitemId" : 7 , "prodId" : 3 , "qty" : 1 }
 ,  { "id" : "bolid" , "name" : "customer 2" , "orderId" : 2 , "orderData" : "12/2/2013" , "lineitemId" : 2 , "prodId" : 6 , "qty" : 6 }
 ,  { "id" : "bolid" , "name" : "customer 2" , "orderId" : 2 , "orderData" : "12/2/2013" , "lineitemId" : 3 , "prodId" : 9 , "qty" : 7 }
 ]

Notice that the template has omitted the '__a5crc' in the input property. The template indicated which properties were to be extracted from the input JSON. It also indicates that the property name should be called in the output JSON.

For example, the template indicates:

"id" : "id"

Had that been:

"id" : "CustomerId"

The output JSON would have named the 'id' property 'CustomerId'.

Here is a simpler example:

dim json as c 
json = <<%str%
[
    {"id" : 1, "name": "John", "kids" : [ {"name": "callie"},{"name" : "griffin"} ]},
    {"id" : 2, "name": "Tom", "kids" : [ { "name" : "betty" } ]}
]
%str%

dim template as c
template = <<%str%
{"id" : "id", "name" : "firstname", "kids" : [ {"name": "name"} ] }
%str%

dim json2 as c 
json2 = json_flatten(json,template)
json2 = json_reformat(json2)

Here is what json2 looks like:

? json2
= [
    {
        "id": 1,
        "firstname": "John",
        "name": "callie"
    },
    {
        "id": 1,
        "firstname": "John",
        "name": "griffin"
    },
    {
        "id": 2,
        "firstname": "Tom",
        "name": "betty"
    }
]

The json_flatten() function can also be used to simply map property names in the input JSON to new property names in the output JSON. For example, consider the following script:

dim json as c 
json = <<%str%
[
    {"id" : 1, "name": "John"},
    {"id" : 2, "name": "Tom"}
]
%str%

dim template as c
template = <<%str%
{"id" : "id", "name" : "firstname"}
%str%

dim json2 as c 
json2 = json_flatten(json,template)
json2 = json_reformat(json2)
showvar(json2)

The resulting JSON will look like this:

[
    {
        "id": 1,
        "firstname": "John"
    },
    {
        "id": 2,
        "firstname": "Tom"
    }
]

See Also