How to access a specific field of a JSON object using JAVA

Question

I’m using Java to get information from Twitter and the REST client Elasticsearch.

As a test I did a PUT of info in JSON and then used the performRequest to obtain a specific element.

//create a json to PUT at the ES
    Map<String, String> params2 = Collections.emptyMap();
    String jsonString = "{" +
                "\"user\":\"Luisinho\"," +
                "\"postDate\":\"1988\"," +
                "\"message\":\"esta a começar a andar\"" +
            "}";
    HttpEntity entity = new NStringEntity(jsonString, ContentType.APPLICATION_JSON);
    Response response4 = restClient.performRequest("PUT", "/posts/doc/2", params, entity);


    //Search the document using Query Params

    Map<String, String> paramMap = new HashMap<String, String>();
    paramMap.put("q", "user:Luisinho");
    paramMap.put("pretty", "true");

    Response response5 = restClient.performRequest("GET", "/posts/_search",
                                                               paramMap);

    System.out.println(EntityUtils.toString(response5.getEntity()));
    System.out.println("Host -" + response5.getHost() );

And I got the desired element this way:

   {
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 0.2876821,
    "hits" : [
      {
        "_index" : "posts",
        "_type" : "doc",
        "_id" : "2",
        "_score" : 0.2876821,
        "_source" : {
          "user" : "Luisinho",
          "postDate" : "1988",
          "message" : "esta a começar a andar"
        }
      }
    ]
  }
}

Host -http://localhost:9200

1- It is possible to obtain this information already as a JSON object?

2- Since I don’t know how to do the first one, I converted that information to a JSON object, but how do I get the value of the key "message" which is what interests me?

I tried something like:

String nova=EntityUtils.toString(response5.getEntity());
JSONObject jsonObj = new JSONObject(nova);
String message = jsonObj.getJSONObject("hits").getString("message");
        System.out.println("JSON  "+message);

But I can’t get the desired value.

Answer 1

To make it easier to get the value "message". Create a pojo with all fields returned from json. Once this is done, use the GSON library to convert your json to the pojo created. That way you can get the value without problems!

Something like that:

Gson gson = new Gson();
String jsonInString = "   {
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 0.2876821,
    "hits" : [
      {
        "_index" : "posts",
        "_type" : "doc",
        "_id" : "2",
        "_score" : 0.2876821,
        "_source" : {
          "user" : "Luisinho",
          "postDate" : "1988",
          "message" : "esta a começar a andar"
        }
      }
    ]
  }
}";
PojoCriado pojoCriado= gson.fromJson(jsonInString, PojoCriado.class);
pojoCriado.getHits.getMessage();