Sunday, 1 July 2018

Map Operator in Dataweave Language


The Map Operator

This blog explains about Map operator in Dataweave , how to use the map operator. The as operator is also featured in this example. Take an JSON list of books and use DataWeave to output a JSON version of the Item list. It goes through each JSON book element from the JSON Array input, simply using the map operator. And transforms to JSON item Array
Consider the following Input:
{
    "books": [
      {
        "-category": "cooking",
        "title": {
          "-lang": "en",
          "#text": "Everyday Italian"
        },
        "author": "Giada De Laurentiis",
        "year": "2005",
        "price": "30.00"
      },
      {
        "-category": "children",
        "title": {
          "-lang": "en",
          "#text": "Harry Potter"
        },
        "author": "J K. Rowling",
        "year": "2005",
        "price": "29.99"
      },
      {
        "-category": "web",
        "title": {
          "-lang": "en",
          "#text": "XQuery Kick Start"
        },
        "author": [
          "James McGovern",
          "Per Bothner",
          "Kurt Cagle",
          "James Linn",
          "Vaidyanathan Nagarajan"
        ],
        "year": "2003",
        "price": "49.99"
      },
      {
        "-category": "web",
        "-cover": "paperback",
        "title": {
          "-lang": "en",
          "#text": "Learning XML"
        },
        "author": "Erik T. Ray",
        "year": "2003",
        "price": "39.95"
      }
    ]
}

The Dataweave transformation logic as below 
%dw 1.0
%output application/json
---
items: payload.books map {
      type: "book",
      price: $.price as :number,
      properties: {
        title: $.title,
        author: $.author,
        year: $.year as :number
      }
}

The output as follows
{
  "items": [
    {
      "type": "book",
      "price": 30.00,
      "properties": {
        "title": {
          "-lang": "en",
          "#text": "Everyday Italian"
        },
        "author": "Giada De Laurentiis",
        "year": 2005
      }
    },
    {
      "type": "book",
      "price": 29.99,
      "properties": {
        "title": {
          "-lang": "en",
          "#text": "Harry Potter"
        },
        "author": "J K. Rowling",
        "year": 2005
      }
    },
    {
      "type": "book",
      "price": 49.99,
      "properties": {
        "title": {
          "-lang": "en",
          "#text": "XQuery Kick Start"
        },
        "author": [
          "James McGovern",
          "Per Bothner",
          "Kurt Cagle",
          "James Linn",
          "Vaidyanathan Nagarajan"
        ],
        "year": 2003
      }
    },
    {
      "type": "book",
      "price": 39.95,
      "properties": {
        "title": {
          "-lang": "en",
          "#text": "Learning XML"
        },
        "author": "Erik T. Ray",
        "year": 2003
      }
    }
  ]
}

The flow.xml as follows

<?xml version="1.0" encoding="UTF-8"?>

<mule xmlns:dw="http://www.mulesoft.org/schema/mule/ee/dw" xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation"
xmlns:spring="http://www.springframework.org/schema/beans" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd
http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
http://www.mulesoft.org/schema/mule/ee/dw http://www.mulesoft.org/schema/mule/ee/dw/current/dw.xsd">
    <http:listener-config name="HTTP_Listener_Configuration" host="0.0.0.0" port="8082" basePath="dw" doc:name="HTTP Listener Configuration"/>
    <flow name="books_to_itemsFlow">
        <http:listener config-ref="HTTP_Listener_Configuration" path="/" doc:name="HTTP"/>
        <dw:transform-message doc:name="Transform Message">
            <dw:set-payload><![CDATA[%dw 1.0
%output application/json
---
items: payload.books map {
      type: "book",
      price: $.price as :number,
      properties: {
        title: $.title,
        author: $.author,
        year: $.year as :number
      }
}]]></dw:set-payload>
        </dw:transform-message>
    </flow>
</mule>


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