Custom Data Formats Example

This repo shows how to create a custom Data format.

Steps

In order to create a Custom Data Format we need to create a Module (i.e ./src/main/resources/org/mule/weave/simplefixedwidth/FixedWidth.dwl) where the logic for reading and writing is going to be defined.

Define The extension

In order to do this define a variable with type DataFormat

@DataFormatExtension
var ndjson: DataFormat<SchemaUrlSettings, SchemaUrlSettings & EncodingSettings> = {
  //All the mime types accepted by this DataFormat
  acceptedMimeTypes: ["application/x-fw", "application/x-fixed-width"],  
  //Reference to the function that is going to be used for transforming the Binary value into the properer DataWeave value
  reader: readFixedWidth,
  //Reference to the function that will transform the DataWeave value into a Binary data
  writer: writeFixedWidth
}

Within this value define the properties of

• acceptedMimeTypes : The defines the mimeTypes that are going to be handled by this DataFormat
• reader: References to the reader function
• writer: Reference to the writer function

Write reader function

The read function will receive 3 parameters.

• The first one the content of the Binary to be read and transform to a Value.
• The second one the encoding to be used to read this content.
• The third one is the configuration settings. The type of this is defined by the DataFormat implementer and is going to be used to hint the user on what settings are valid.

    fun readFixedWidth(content: Binary, charset: String, settings: SchemaUrlSettings): Any = ???

Inside this function the user needs to write the logic to parse this content.

Write writer function

The write function will receive two parameters.

• The first one is theValue to write and transform it into the Binary
• The second one is the settings The type of this is defined by the DataFormat implementer and is going to be used to hint the user on what settings are valid.

    fun writeFixedWidth(theValue: Any, settings: SchemaUrlSettings & EncodingSettings): Binary = ???

Inside this function the user needs to write the logic to write the value.

Register the Extension

Create a file in src/main/resources/META-INF/dw-extensions.dwl that will contain a reference to the Module so that DataWeave knows where the extensions are.

[
    "org::mule::weave::simplefixedwidth::FixedWidth"
]

Deploy and Use

Last just deploy it to maven and reference it from the pom.xml in studio