====== HTTP Rest Client with JSON ======
We can do a HTTP rest request to a server in Grails. Here is how.

===== Add Rest Client Dependencies in build.gradle =====
In order to use rest client, first add the following in the ''build.gradle''
<code>
compile "org.grails:grails-datastore-rest-client"
</code>

===== Do Rest Request in a Controller =====
You can do it in any of your controller's method. In this example, it will convert a string into JSON, and then send it to the server ''http://127.0.0.1:8080/api/'', and finally get a JSON responds from that server.
<code>
def callapi() {
	String s = '{' +
			'   "name": "John",\n' +
			'   "age": 30,\n' +
			'   "cars": [\n' +
			'       { "name" : "Ford" , "models" : ["Fiesta", "Focus", "Mustang"] },\n' +
			'       { "name" : "BMW" , "models" : ["320", "X3", "X5"] },\n' +
			'       { "name" : "Fiat" , "models" : ["500", "Panda"] }\n' +
			'   ]' +
			'}'
	def jsonSlurper = new JsonSlurper()
	def jsonObject= jsonSlurper.parseText(s)
	RestBuilder rest = new RestBuilder()
	String url = "http://127.0.0.1:8080/api"
	RestResponse restResponse = rest.post(url) {
		accept("application/json")
		contentType("application/json")
		json {jsonObject}
	}

	JSONElement jsonElement = restResponse.json
	render(jsonElement)
}
</code>

or we can do it like this with a Map<String, Object> as JSON, and timeout for the connection.
<code>
        Map<String, Object> responseData = [
                "messageID"        : "testing-message",
                "dateTime"         : "2000-01-01-01:02:03",
                "responseToMessage": "aaaaaa",
        ]

        RestBuilder rest = new RestBuilder(connectTimeout: 1000, readTimeout:60000)
        String url = "http://127.0.0.1:8080/api"
        RestResponse restResponse = rest.post(url) {
            accept("application/json")
            contentType("application/json")
            json {
                responseData
            }
        }

        JSONElement jsonElement = restResponse.json
        render(jsonElement)
</code>

===== Additional Information =====
Here is how the server code looks like
<code>
class ApiController {

    def index() {
        JSONObject jsonObject = request.JSON as JSONObject
        render(jsonObject as JSON)
    }
}
</code>

and the result from the client looks like this:
{{ :grails:grails_rest_client_json.png?nolink&200 |}}