Get less from your REST! A small scala/play library for filtering and projecting json results from REST calls

In your build.sbt include:

libraryDependencies += "com.wellfactored" %% "restless" % "0.4.0"

restless is implemented as restless-core and restless-play-json components. The core package implements the query parser that will generate an AST and play-json provides an implementation of an execution engine for the AST that applies it to documents made up of PlayFramework JsObjects. core depends only on Rob Norris (tpolecat)'s att-core library. restless-play-json will pull in com.typesafe.play-json and associated dependencies.

restless implements a simple query language to filter lists of results. For example, of you had the following json output from your api call:

[
  {
    "foo" : "bar",
    "x" : 14
    "y" : 13
  },
  {
    "foo" : "baz",
    "x" : 14,
    "y" : 15
  }
]

The you could use a query such as foo = baz to filter this down to

[
  {
    "foo" : "baz",
    "x" : 14,
    "y" : 15
  }
]

or something a bit more complex like x > y. It also supports compound expressions such as:

• a = b and c > 3
• (a = b or c < 3) and d != "foo"

Numeric queries can include all the usual comparison operators, namely =, !=, <, >, <= and >=.

String comparisons are case-insensitive and can be one of:

• =
• !=
• starts-with or starts with
• ends-with or ends with
• contains

There are still some arbitrary restrictions in the query syntax. For example, you cannot put a constant on the left-hand-side of a comparison at the moment.

Paths to string values can only be compared against string literals - it should be possible to compare them against other paths.

Many thanks to Rob Norris (tpolecat) for the lovely atto parser and his help when I ran into some recursion issues. If you want a nice small, easy-to-use parser then check it out - https://github.com/tpolecat/atto