Converting a sequence of Scala objects to JSON using the Play Framework

The code in this blog post shows how to convert a Seq of Scala objects to their equivalent JSON representation. Specifically, I’m working on an application to display Twitter data, and I want to convert a Seq[Tweet] to its JSON.

My goal in the following code is to return some JSON that looks like this:

I get the actual data by querying Twitter, but that isn’t important. As far as the data source goes, the only important thing is that I call the TwitterDao.getTweetsInListAsSeq method, which returns an Option[Seq[Tweet]] , and I create the JSON from that Seq .

The Play Framework Controller

My Play Framework Controller code looks like this:

The peeps method in that code is a normal Play Action method. I need to use Async as well, but that’s not important here. (I also have an entry for it in the routes file, connecting it to a URI and request method, but that isn’t important for this example.)

The important code is the convertTweetsToJson method. It used to be much longer, but since I’m now using a Format object, the body of the method is only this:

Because of this, the convertTweetsToJson method isn’t really needed, but I’ve kept it in so you can compare it to a similar method below.

Creating an implicit Format object

To get that code to work I had to define this other code in a file named Tweet.scala:

The important part of this code is the writes method in the implicit TweetFormat object; it’s used to serialize the Scala object Tweet to its JSON representation. The code shown is a fairly standard implementation of this method.

Given all of that code, my peeps method returns the desired JSON.

Another approach

Before I thought to use the approach of creating an implicit Format object, my convertTweetsToJson method looked like this:

This code returns the same JSON as the previous approach, and it’s also simpler. I also think it’s a great use of the map method. (I found an example like this in the Play docs.) Frankly, for my purposes, I’ll probably go back to using it, but I wanted to show the other approach because it may come in handy in other situations.