Step1.md

Step 1: Creating JSON

TODO

• Insert on the right guide page: Play JSON 2.6 -> 2.7

JSON values

JSON types

See JsValue

All JsValues can pattern match easily, except JsObject because the order of its field/value entries will count, but this not wanted because in JSON object there is no order.

import play.api.libs.json._
Json.parse(""" "toto" """) match {
    case JsString(str) => s"""we have the string "$str""""
    case other => s"""Hu ? I didn't expect $other..."""
}

Here, please note the trick on JsNumber: BigDecimal has no unapply.

import play.api.libs.json._
Json.parse("""["toto"], 1, true]""") match {
    case JsArray(Seq(JsString("toto"), JsNumber(v), JsBoolean(true))) if v == BigDecimal("1")=> true
    case other => false
}

In the above code, JsBoolean(true) could be replaced with JsTrue.

Create JSON by parsing a string

See string parsing

Create JSON by building it programmatically

See class construction

Use path

See traversing a JSON structure

validate or as ?

as

as throws exception on failure asOpt returns Some(result) or None if failure

See as and asOpt

validate

validate return a JsResult, than can be either JsSuccess or JsError. You can pattern match or use usual map/flatMap/fold etc.

See validate

Exercise

Complete Step1_CreatingJsons; Step 1 tests must compile and pass.

Next

Checkout Step2 branch and go to Step2: Reads