GSON

What is first

GSON is a very nice Java library to map JSON into Java objects (and vice versa). Thanks to OKFN's Ross Jones for https://github.com/okfn/CKANClient-J (my fork) and it's eloquent use of GSON. My notes about this are at #sadi-using-java-take-2.

Let's get to it

List getDatasetRevisions(String datasetName) uses GSON.

• First, get a JSON string (with GET or POST).
• Next, create an inner class for the response.

Arrays up front

When the JSON looks like:

         [
            {
               "uri":"http://dbpedia.org/resource/Edinburgh",
               "numDuplicates":"176",
               "duplicates": [
                 "http://dbpedia.org/resource/Eidyn",
                 "http://dbpedia.org/resource/Embra",
                 "http://dbpedia.org/resource/Embro",
                 "http://yago-knowledge.org/resource/Edinburgh",
                 "http://yago-knowledge.org/resource/Areas_of_Edinburgh",
                 "http://yago-knowledge.org/resource/Edinburgh_Inspiring_Capital"
               ]
            }
         ]

use (thanks to stackoverflow):

public class MyClass {

	@Override
	public void doMyJSONThing() {
              String content; // The JSON String.
              ...
	      Gson       gson    = new Gson();
	      JsonParser jparser = new JsonParser();
	      for( JsonElement object : jparser.parse(content).getAsJsonArray() ) {
	         MyClass.URI uri = gson.fromJson(object, MyClass.URI.class);
	         System.out.println(uri.uri);
	         for( String duplicate : uri.duplicates ) {
	            System.out.println(duplicate);
	         }
	      }
	   }
	}

	/**
	 * For GSON
	 */
	public class URI {
	   public String       uri;        // The "uri" attribute in the JSON object
	   public List<String> duplicates; // The "duplicates" attribute in the JSON object
	}
}