How to create json message string with indentation in java

Recently I came across an ugly string concatenation in one of our legacy codebase or the one I did not came across for a long time.

The string concatenation was there to construct as JSON string. The JSON string was then parsed as a message template for MQTT topics.

At first sight, I knew it gotta go and something bit more cleaner piece of code should replace it. So I was looking for options to do a better job. Then I found something below:

org.json library#

Maven#

<dependency>
	 <groupId>org.json</groupId>
	 <artifactId>json</artifactId>
	 <version>20090211</version>
</dependency>

Gradle#

compile "org.json:json:20090211"

Using the JSONObject of this library I was able to replace the ugly string concatenation with something like below:

JSONObject in action#

new JSONObject()
	.put("name", "Ashok M A")
	.put("website", "https://ashokma.com")
	.put("address", new JSONObject()
		.put("houseNumber", "1234")
		.put("street", "Woonboulevard")
		.put("city", "Utrecht")
		.put("country", "The Netherlands")
	)
	.put("skills", new JSONArray(
			Arrays.asList("Angular", "Spring Boot")))
	.toString(4); // indentation

The above beautiful piece of code gives us the below JSON string.

{
	"address": {
		"city": "Utrecht",
		"country": "The Netherlands",
		"houseNumber": "1234",
		"street": "Woonboulevard"
	},
	"name": "Ashok M A",
	"skills": ["Angular", "Spring Boot"],
	"website": "https://ashokma.com"
}

Yes, you can also construct by nesting arrays into objects and vice versa. \O/

The keys are sorted by default. In JSON format that does no harm.

I do not have to show you the ugly concatenation to sell the point here but this org.json lib itself does pretty good job and I am sure you would agree as well.