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JSON Format

MIME Type: application/json

ID: json

In the JSON data format, values map one-to-one with DataWeave values. JSON supports String, Boolean, Number, Null, Object, and Array types. DataWeave supports each of these values natively.

The DataWeave reader for JSON input supports the following parsing strategies:

  • Indexed

  • In-Memory

  • Streaming

To understand the parsing strategies that DataWeave readers and writers can apply to this format, see DataWeave Parsing Strategies.

Examples

The following examples show uses of the JSON format:

Example: Represent JSON in the DataWeave (dw) Format

This example shows how JSON input is represented in the DataWeave (dw) format.

Input

The following JSON object serves as the input payload to the DataWeave source.

{
  "name": "Matias",
  "age": 8,
  "male": true,
  "kids": null,
  "brothers": ["Pedro", "Sara"]
}

Source

The DataWeave script transforms the JSON input payload to the DataWeave (dw) format and MIME type.

output application/dw
---
payload

Output

Notice that only the keys of the JSON input and the application/dw output differ. The JSON keys are surrounded by quotation marks. These DataWeave (dw) keys do not require quotation marks. See Valid Keys for details.

{
  name: "Matias",
  age: 8,
  male: true,
  kids: null,
  brothers: [
    "Pedro",
    "Sara"
  ]
}

Example: Convert Repeated XML Elements to JSON

This example shows how to convert repeated XML elements to JSON.

Note that XML encodes collections using repeated (unbounded) elements. DataWeave represents unbounded elements by repeating the same key.

Input

The following XML data contains repeating child elements with the key name. This XML serves as the input payload to the DataWeave source.

<?xml version='1.0' encoding='UTF-8'?>
<friends>
  <name>Mariano</name>
  <name>Shoki</name>
  <name>Tomo</name>
  <name>Ana</name>
</friends>

Source

The following DataWeave script takes the XML input as its payload and outputs that payload in the JSON format.

The script selects the name elements from the XML input and uses the DataWeave map function to map the values of those elements into an array of objects. Each object in the array takes the form { name : item }, where item is the value of the name element. The entire array serves as the value of the friends key.

%dw 2.0
output application/json
---
friends: payload.friends.*name map (
            (item, index) -> {name: item}
         )

Output

The DataWeave script outputs the following JSON object.

{
  "friends": [
    {
      "name": "Mariano"
    },
    {
      "name": "Shoki"
    },
    {
      "name": "Tomo"
    },
    {
      "name": "Ana"
    }
  ]
}

Example: Stream JSON Data

To demonstrate streaming, the following example streams a JSON file by reading each element in an array one at a time.

Input

The JSON input payload serves as input for the XML configuration.

JSON Input (truncated):
{ "myJsonExample" : [
    {
      "name" : "Shoki",
      "zipcode": "95838"
    },
    {
      "name" : "Leandro",
      "zipcode": "95823"
    },
    {
      "name" : "Mariano",
      "zipcode": "95815"
    },
    {
      "name" : "Cristian",
      "zipcode": "95815"
    },
    {
      "name" : "Kevin",
      "zipcode": "95824"
    },
    {
      "name" : "Stanley",
      "zipcode": "95841"
    }
  ]
}

XML Configuration

The following XML configuration streams JSON input.

<file:config name="File_Config" doc:name="File Config" />
<flow name="dw-streaming-jsonFlow" >
  <scheduler doc:name="Scheduler" >
    <scheduling-strategy >
      <fixed-frequency frequency="1" timeUnit="MINUTES"/>
    </scheduling-strategy>
  </scheduler>
  <file:read doc:name="Read"
     config-ref="File_Config"
     path="${app.home}/myjsonarray.json"
     outputMimeType="application/json; streaming=true"/>
  <ee:transform doc:name="Transform Message" >
    <ee:message >
      <ee:set-payload ><![CDATA[%dw 2.0
output application/json
---
payload.myJsonExample map ((element) -> {
returnedElement : element.zipcode
})]]></ee:set-payload>
    </ee:message>
  </ee:transform>
  <file:write doc:name="Write"
    path="/path/to/output/file/output.json"
    config-ref="File_Config1"/>
  <logger level="INFO" doc:name="Logger" message="#[payload]"/>
</flow>
  • The streaming example configures the HTTP listener to stream the JSON input by setting outputMimeType="application/json; streaming=true". In the Studio UI, you can set the MIME Type on the listener to application/json and the Parameters for the MIME Type to Key streaming and Value true.

  • The DataWeave script in the Transform Message component iterates over the array in the input payload and selects its zipcode values.

  • The Write operation returns a file, output.json, which contains the result of the transformation.

  • The Logger prints the same output payload that you see in output.json.

Output

The JSON streaming example produces a JSON array of objects.

[
  {
    "returnedElement": "95838"
  },
  {
    "returnedElement": "95823"
  },
  {
    "returnedElement": "95815"
  },
  {
    "returnedElement": "95815"
  },
  {
    "returnedElement": "95824"
  },
  {
    "returnedElement": "95841"
  }
]

Configuration Properties

DataWeave supports the following configuration properties for JSON.

Reader Properties (for JSON)

The JSON format accepts properties that provide instructions for reading input data.

Parameter Type Default Description

streaming

Boolean

false

Property for streaming input. Use only if entries are accessed sequentially. Valid values are true or false. The input must be a top-level array. For more on streaming in DataWeave, see DataWeave Readers.

Writer Properties (for JSON)

The JSON format accepts properties that provide instructions for writing output data.

Parameter Type Default Description

bufferSize

Number

8192

Size of the writer buffer.

deferred

Boolean

false

Property for deferred output. Valid values are true or false.

duplicateKeyAsArray

Boolean

false

If duplicate keys are detected in an object, the writer changes the value to an array with all those values. Valid values are true or false. Note that JSON language does not allow duplicate keys with one same parent, so the duplication usually raises an exception.

encoding

String

UTF-8

The character set to use for the output.

indent

Boolean

true

Indicates whether to indent the JSON code for better readability or to compress the JSON into a single line. Valid values are true or false.

skipNullOn

String

null

Skips null values in the specified data structure. By default, it does not skip the values. Valid values are arrays, objects, or everywhere.

  • arrays
    Ignore and omit null values inside arrays from the JSON output, for example, with output application/json skipNullOn="arrays".

  • objects
    Ignore key-value pairs that have null as the value, for example, with output application/json skipNullOn="objects".

  • everywhere
    Apply skipNullOn to arrays and objects, for example, output application/json skipNullOn="everywhere".

writeAttributes

Boolean

false

Indicates whether to add attributes of a key to children of the key. The new attribute key name will start with @. Valid options are true or false.

Supported MIME Types (for JSON)

The JSON format supports the following MIME types.

MIME Type

*/json

/+json

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