Spark server with json schema validation, running on groovy

spark-validation.groovy

@Grab('com.github.fge:json-schema-validator:2.2.6')
@Grab('com.sparkjava:spark-core:2.1')

import spark.*
import static spark.Spark.*

import com.github.fge.jackson.JsonLoader
import com.github.fge.jsonschema.main.JsonSchemaFactory

def factory = JsonSchemaFactory.byDefault()
def jsonContents = JsonLoader.fromString('{"properties":{"id":{"type":"string"},"title":{"type":"string"}},"required":["id","title"]}')
def schema = factory.getJsonSchema(jsonContents)

println 'Starting server'
post '/posts', { req, res -> 'Hello World' }
before '/posts', { req, res -> 
	println req.body()
	def r = schema.validate(JsonLoader.fromString(req.body()))
	if (! r.isSuccess()) {
		halt(400, r.collect({ it.message}).join(','))
	}
}