Groovy - Creating JSON using JsonOutput

Groovy provides JsonOutput class as a primary tool to convert Groovy Maps, lists or even nested structures into JSON Strings. In this chapter, we're exploring them with examples.

Creating JSON from a Groovy Map

Example.groovy

import groovy.json.JsonOutput

// Creating JSON from a map
def employee = [name: "Alice", age: 28, city: "Seattle", dept: "Admin"]

// convert Map to JSON
def jsonFromMap = JsonOutput.toJson(employee)

// prints Json
println jsonFromMap

Output

When we run the above program, we will get the following result.

{"name":"Alice","age":28,"city":"Seattle","dept":"Admin"}

Creating JSON from a Groovy List

Example.groovy

import groovy.json.JsonOutput

// Creating JSON from a list
def fruits = ["apple", "banana", "mango"]

// convert List to JSON
def jsonFromList = JsonOutput.toJson(fruits)

println jsonFromList

Output

When we run the above program, we will get the following result.

["apple","banana","mango"]

Creating JSON from a Groovy Nested Structure

Example.groovy

import groovy.json.JsonOutput

// Creating JSON from a nested structure
def stationary = [
   id: 1,
   items: [
      [name: "Book", price: 17.99],
      [name: "Pen", price: 2.51]
   ],
   total: 20.50
]
def jsonFromNestedStruct = JsonOutput.toJson(stationary)
println jsonFromNestedStruct

Output

When we run the above program, we will get the following result.

{"id":1,"items":[{"name":"Book","price":17.99},{"name":"Pen","price":2.51}],"total":20.50}

Pretty Printing JSON

We can use JsonOutput.prettyPrint() to print JSON with proper indentation and breaks.

Example.groovy

import groovy.json.JsonOutput

// Creating JSON from a nested structure
def stationary = [
   id: 1,
   items: [
      [name: "Book", price: 17.99],
      [name: "Pen", price: 2.51]
   ],
   total: 20.50
]
def jsonFromNestedStruct = JsonOutput.toJson(stationary)
def prettyJson = JsonOutput.prettyPrint(jsonFromNestedStruct)
println prettyJson

Output

When we run the above program, we will get the following result.

{
    "id": 1,
    "items": [
        {
            "name": "Book",
            "price": 17.99
        },
        {
            "name": "Pen",
            "price": 2.51
        }
    ],
    "total": 20.50
}