Graphically modeling a JSON message in a message map

In the Graphical Data Mapping editor, you can use the Add User-Defined function to create a JSON message that contains JSON objects, JSON arrays, or both.

Complete the following steps to create a JSON message for which you do not have a schema model:

1. Create a message map. Select one of the following JSON supplied models as the input or output of the map:
   • JSON (JSON object message model supplied by IBM) to create a JSON object message
   • JSON (JSON array message model supplied by IBM) to create a JSON array message

   For more information, see Creating a message map.

2. Qualify the content under the Data element by using the Add User-Defined function.
   A JSON message consists of name-value pairs, which are known as JSON objects, and ordered collections of values, which are known as JSON arrays.

   1. To define a JSON object in the JSON output message, use the Add User-Defined function to add an element, and select one of the supported simple types. For more information, see Graphically modeling a JSON object in a message map.
   2. To define a JSON array in the JSON output message, use the Add User-Defined function to add an element, and select JSONArray_Default as its type. For more information, see Graphically modeling a JSON array in a message map.
   3. To define a multidimensional JSON array in the JSON output message, use the Add User-Defined function to add multiple elements, and select JSONArray_Default as their types. For more information, see Graphically modeling a multidimensional JSON array in a message map.

   Note: When you use the Graphical Data Mapping editor to transform a JSON message, ensure that the JSON element names that you define by using the Add User-Defined function are valid according to the XML rules for naming elements. JSON allows a wider range of characters than XML, for example a JSON object might include the @ character, however, the Graphical Data Mapping editor allows only element names that are valid in XML or XPath.
3. Define transforms between the input elements and the output elements.
   • Use the Assign transform to set a fixed value without the use of input data.
   • Use the Create transform to create an empty JSON object, or a NULL JSON object, without the use of input data
   • Use the Move transform to copy an input element value to the output element.
   • Use the If transform, a custom transform, or the XPath transform to define the condition that determines the value of an output element.
   • Use the Append transform, the Group transform, the For Each transform, the Join transform, a custom transform, or the XPath transform to set the value of a JSON array.
   • Use the Select transform or the Database Routine transform to set the value with data available in a database system.
   • Use the xs:type transform to cast the value of a simple input element to a specific data type.
   • Use the fn:type transform to set the value by using XPATH 2.0 functions.
   • Use the Custom Java transform to enter your own Java™ code.
   • Use the Custom ESQL transform to call your own ESQL code.
   • Use a Custom XPath transform with the function iib:nullValue() to set a JSON object to NULL, or a JSON array to NULL.

   For more information, see Specifying a transform (mapping operation).

{"element1":[{"Nam":"val1","Num":1},{"Nam":"val2","Num":2}]}

 (0x01000000:Object):JSON       = ( ['json' : 0x2f030fa0]
    (0x01000000:Object):Data = (
      (0x01001000:Array):element1 = (
        (0x01000000:Object):Item = (
          (0x03000000:NameValue):Nam = 'val1' (CHARACTER)
          (0x03000000:NameValue):Num = 1 (INTEGER)
        )
        (0x01000000:Object):Item = (
          (0x03000000:NameValue):Nam = 'val2' (CHARACTER)
          (0x03000000:NameValue):Num = 2 (INTEGER)
        )
      )
    )
  )

[{"element1":{"field1":"Sweet","field2":"Flower"},"element2":"me@bbloggs.com"}]

  
(0x01000000:Object):JSON       = ( ['json' : 0x292051a0]
    (0x01001000:Array):Data = (
      (0x01000000:Object):Item = (
        (0x01000000:Object   ):element1 = (
          (0x03000000:NameValue):field1 = 'Sweet' (CHARACTER)
          (0x03000000:NameValue):field2 = 'Flower' (CHARACTER)
        )
        (0x03000000:NameValue):element2 = 'me@bbloggs.com' (CHARACTER)
      )
    )