JSON in Groovy / Grails

Question

I'm trying to access a site via their JSON export.

The URL is: http://neotest.dabbledb.com/publish/neotest/f820728c-4451-41f6-b346-8cba54e52c6f/projects.jsonp

I'm using HTTPBuilder to try and accomplish this in Groovy, but am having trouble. I used the example code from http://groovy.codehaus.org/HTTP+Builder to come up with this:

            // perform a GET request, expecting JSON response data
        http.request( GET, JSON ) {
          url.path = 'publish/neotest/f820728c-4451-41f6-b346-8cba54e52c6f/projects.jsonp'

          // response handler for a success response code:
          response.success = { resp, json ->
            println resp.statusLine

            // parse the JSON response object:
            json.responseData.results.each {
              println "  ${it.titleNoFormatting} : ${it.visibleUrl}"
            }
          }
        }

however, when I run the unit test for the method I simply get "No such property: GET for class: ProjectController groovy.lang.MissingPropertyException: No such property: GET for class: ProjectController" which I'm having trouble understanding.

Answer 1

I'm not familiar with HTTPBuilder, but looking at the documentation, you might be able to get by with replacing

http.request( GET, JSON ) {

with

http.request( Method.GET, ContentType.JSON ) {

You may also have to:

import groovyx.net.http.Method
import groovyx.net.http.ContentType

I'm basing this off of the documentation for HttpBuilder.request(), which calls for a Method and an Object (which can be a ContentType).

Answer 2

There are a few problems with your sample code. First of all, to access GET and JSON that way, you need to statically import them:

import static groovyx.net.http.Method.GET
import static groovyx.net.http.ContentType.JSON

That will make the code compile, but not run successfully. Your url.path value needs a leading '/' (as shown on the HTTPBuilder page). More importantly, the JSON that comes back from the URL you're referencing has a totally different structure from that returned by the example code that performs a Google search. If you load your URL into the very handy JSON Formatter service at CuriousConcept, you'll see the structure. Here's code that would display some of the JSON data:

println json.name
println json.id
json.fields.each {
  println it
}

By the way, there's a breaking change in version 0.5.0 of HTTPBuilder that is relevant to this code. As the RC-1 release announcement states,

The HTTPBuilder class' URL property has been renamed to uri

So, if you move to 0.5.0 at some point, you'll need to use uri.path instead of url.path

Answer 3

Although not answering the original question I noticed you asked about other possible libraries. Disregarding Groovy which I haven't used for this, the best and simplest Java library for building a web services client is Jersey in my opinion, hands down.

Answer 4

If you just want to fetch the data, you could do it in Grails this way:

import grails.converters.*;

def url = new URL("http://neotest.dabbledb.com/publish/neotest/f820728c-4451-41f6-b346-8cba54e52c6f/projects.jsonp")
def response = JSON.parse(url.newReader()) // response is an instance of JSONObject (see Grails API docs)

println response.toString(3) // Pretty-printed output
response.each { key, value ->
    println "$key = $value"
}

(just as a simple alternative)