play-jsonpath

play-jsonpath is a jsonpath implementation that works with play's json library.

• $: start a jsonpath expression on a JsonValue
• *: select any children of the current node
• ?(selector): selects one or no child
• *(selector): selects all children that meets the selector
• %: current node

Usage

For the following json document that I borrowed from gatling's implementation:

{ "store": {
    "book": [
      { "category": "reference",
        "author": "Nigel Rees",
        "title": "Sayings of the Century",
        "price": 8.95,
        "ratings": {
          "klass": "R"
        }
      },
      { "category": "fiction",
        "author": "Evelyn Waugh",
        "title": "Sword of Honour",
        "price": 12.99,
        "published": "2015-04-07T12:00:00.000Z"
      },
      { "category": "fiction",
        "author": "Herman Melville",
        "title": "Moby Dick",
        "isbn": "0-553-21311-3",
        "price": 8.99,
        "ratings": {
          "klass": "PR"
        },
        "published": "2016-04-07T12:00:00.000Z"                
      },
      { "category": "fiction",
        "author": "J. R. R. Tolkien",
        "title": "The Lord of the Rings",
        "isbn": "0-395-19395-8",
        "price": 22.99
      }
    ],
    "bicycle": {
      "XGZ193-R" : {
        "color": "red",
        "price": 19.95
      },
      "XGZ193-G" : null,
      "XGZ193-B" : {
        "color": "blue",
        "price": 21.95
      }
    }
  }
}

select third book's klass:

scala> val js = Json.parse(jsonString)
scala> js.$.store.book(2).ratings.klass.as[String]
"PR"

select all klasses:

scala> val store = js.$.store
scala> store.book(*).ratings.klass.as[List[String]]
List("R", "PR")

a wild-card for the index of an array can be omitted:

scala> store.book.ratings.klass.as[List[String]]
List("R", "PR")

find a book with the price higher than 8.95:

scala> store.book(?(%.price > 8.95)).title.as[String]
"Sword of Honour"

find a book with klass of PR:

scala> store.book(?(%.ratings.klass == "PR")).title.as[String]
"Moby Dick"

find a blue bicylce's price:

scala> store.bicycle(?(%.color == "blue")).price.as[Double]
21.95

find titles of all books of the price <= 20 and the fiction category:

scala> store.book(*(%.price <= 20 && %.category == "fiction")).title.as[List[String]]
List("Sword of Honour","Moby Dick")

find all books' klasses:

scala> store.book.*.klass.as[List[String]]
List("R", "PR")

More to customize

Suppose that your json document has ratings.class instead of ratings.klass. In scala, 'class' is a keyword that you cannot use as a function name. Your jsonpath expression has to use 'klass'. However, you can still keep 'class' in your json documents. Make this implicit path naming available to your code.

implicit val pathNaming = new PathNaming {
  def toJsonKey(javaKey: String) = if(javaKey == "klass") "class" else javaKey
}

Likewise, you can have your own Reads[Date] implemented.

implicit val dateReads = new Reads[DateTime] {
  def reads(js: JsValue) = {
    JsSuccess(new SimpleDateFormat("yyMMddHHmmssZ").parse(js.as[String]))
  }
}

What's next

Scala macro version is currently under development on v1.1. The scala dynamics is used only during compile time to allow dynamic key names. By the time compilation completes, the scala AST code is converted into play framework's $bslash functions.

scala> store.book.ratings.klass.as[List[String]]

The above code block is re-written to the following during compilation, thus removing the runtime overhead of scala dynamics.

scala> (store \ "book" \ "ratings" \ "klass").as[List[String]]

Jsonpath macro function is backward compatible. To enable the macro, you need to either call PathMacro.$() or PathMacro.pathMacro().

scala> import PathMacro._
scala> ${js.$.store.book.ratings.klass}.as[List[String]]

where js is the JsValue instance. pathMacro() allows to use jsonpath in an entire code block without calling $() over and over.

scala> import PathMacro._
scala> pathMacro{
scala>   val store = js.$.store
scala>   store.bicycle(?(%.color == "blue")).price.as[Double] mustBe 21.95
scala>   store.book(?(%.category == "non-fiction")).price.getOrElse(0.0) mustBe 0.0
scala> }

Samples

• [JsonPathSpec.scala] spec

License

Apache 2

Building

You need sbt installed.

$ git clone https://github.com/youriris/play-jsonpath.git
$ cd play-jsonpath
$ sbt eclipse