Quick and Dirty JSON Builder for Java

If you're writing tests involving JSON or trying to return some basic JSON structure in a simple Play or Spark application here is a simple shorthand notation that can be used to build said response.

Given the following JSON structure,

{
  "title" : "Test Schema",
  "type" : "object",
  "properties" : {
    "firstName" : {
      "type" : "string"
    },
    "lastName" : {
      "type" : "string"
    },
    "age" : {
      "description" : "Age in years",
      "type" : "integer",
      "minimum" : 0
    }
  },
  "required" : [ "firstName", "lastName" ]
}

It is possible to represent this in Java like this,

toJson(of(
    "title", "Test Schema",
    "type", "object",
    "properties", of(
        "firstName", of("type", "string"),
        "lastName", of("type", "string"),
        "age", of(
            "description", "Age in years",
            "type", "integer",
            "minimum", 0
        )
    ),
    "required", new String[] { "firstName", "lastName" }
))

In order to achieve this then 2 static imports must be used,

import static com.google.common.collect.ImmutableMap.of;
import static play.libs.Json.toJson;

Obviously, this assume the use of Guava and Play but we can at least avoid the use of Play (i.e. if you're using some other web framework) by shimming the toJson method using the Jackson ObjectMapper directly e.g.

public JsonNode toJson(Object data) {
    // either provide or create an ObjectMapper
    return new ObjectMapper().valueToTree(data);
}

It's nicer than using, and having to wrangle, a massive string blob because it helps avoid some of accidental syntactical JSON errors that you can make (extra commas, unbalanced braces etc.) when dealing with a raw string. It's also a bit terser than using the Jackson builder directly as that can make deep chaining a bit awkward from what I've experienced.

CAVEAT: I use this in tests and basic webapps were performance is not important in the slightest so I haven't attempted to understand the overhead of using this approach.