MuleSoft DataWeave: Reading From the File

Follow along with this brief tutorial to follow an example of how to read data from files using MuleSoft DataWeave.

Arpan K Sharma

Jan. 20, 22 · Code Snippet

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Before we start, let's go over the following:

readurl (): It is dw-core-function and returns parsed content from source at given classpath-based url. readurl("classpath-based url","contentType").
dynamic selector[()]: Return the value of expression passed in parentheses of dynamic selector [()].

Example of Reading Data From Files

The file in use here is zipcode.json, which has zip codes for different cities in India. It is available at classpath "/src/main/resources/".

Example 1:

Reading data from a file can be achieved by using readUrl() in DataWeave.

Data in the "zipcode.json" file is as follows:

    JSON
   
   {

"Indore" : "455001" ,
"Pune" : "411002",
"Bhopal" : "462003",
"Banglore" : "56004"

}

DataWeave Code, to cath parsed value in dwl variable and map it to a field:

    JSON
   
 

   %dw 2.0
output application/json
var zipcodes = readUrl("classpath://zipcode.json" , "application/json")
---
{
	"usingVar" : zipcodes,
	"directlyUsingURL" : readUrl("classpath://zipcode.json" , "application/json")
}
  

Output:

    JSON
   
 

   {
    "usingVar": {
        "Indore": "455001",
        "Pune": "411002",
        "Bhopal": "462003",
        "Banglore": "56004"
    },
    "directlyUsingURL": {
        "Indore": "455001",
        "Pune": "411002",
        "Bhopal": "462003",
        "Banglore": "56004"
    }
}
  

Example 2:

Mapping a field in response from parsed data of the file can be achieved in a single transform node using "readUrl()" and "dynamic selector [()] for single value".

Data in the "zipcode.json" file:

    JSON
   
   {

"Indore" : "455001" ,
"Pune" : "411002",
"Bhopal" : "462003",
"Banglore" : "56004"

}

Input payload:

    JSON
   
 

   [
    {
        "city": "Indore"
    },
    {
        "city": "Bhopal"
    }
]
  

DataWeave code:

    JSON
   
 

   %dw 2.0
output application/json
var zipcodes = readUrl("classpath://zipcode.json" , "application/json")
---
payload map ((item, index) -> {
  "City": item.city,
  "Zipcode": zipcodes[item.city]
})
  

Output:

    JSON
   
 

   [
    {
        "City": "Indore",
        "Zipcode": "455001"
    },
    {
        "City": "Bhopal",
        "Zipcode": "462003"
    }
]
  

Thanks!

MuleSoft

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