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Json Parsing: How to fetch "body" data inside "body array" using Gson (or better in other java library or notation supported)?

My Rest API is returning the following response, in which only the inner list is required, all data shall be discarded:
{
"meta": [],
"links": [],
"body": [
{
"meta": [],
"links": [],
"body": {
"field1": "value1",
"fieldn": "valuen"
} // <-----
},
{
"meta": [],
"links": [],
"body": {
"field1": "value1",
"fieldn": "valuen"
} // <-----
}
]
}
Is there any way in Gson or another other java library to fetch an array of the body or a straightforward way of doing that? Or maybe even using standard of java 8?
Or, should I use a standard iterator as follows:
//Old way to do this
JSONArray BodyArr = (JSONArray) jsonObject.get("Body");
Iterator<JSONObject> itBody = BodyArr.iterator();
int teller = 0;
while (itBody.hasNext()) {
JSONObject bodyObj = itBody.next();
JSONObject body = (JSONObject) bodyObj.get("Body");
}
Also in mysql we have way to do that using notation ($.body.body[] etc.). Is there any notational way to fetch the object

I think we have a nicely written article on this.
Json object iteration

If you have a class that represents an object in the array, then you can deserialize the JSONArray to an array of that class using public <T> T fromJson​(JsonElement json, java.lang.Class<T> classOfT) throws JsonSyntaxException on the Gson class:
class BodyItem {
public String[] meta;
public String[] links;
public String field1;
public String fieldn;
}
public BodyItem[] getBodyItems(final Gson gson, final JsonObject jsonObject) {
final JsonElement body = jsonObject.get("body");
return gson.fromJson(body, BodyItem[].class);
}
public static void main(final String[] args) {
final String response = "<your REST API JSON response>";
final Gson gson = new Gson();
final JsonObject jsonObject = gson.fromJson(response, JsonObject.class);
final BodyItem[] bodyItems = getBodyItems(gson, jsonObject);
}
If you want a more notational way of accessing fields in Gson objects, you can use JsonObject's convenience accessors:
JsonArray getAsJsonArray​(java.lang.String memberName)
JsonObject getAsJsonObject​(java.lang.String memberName)
JsonPrimitive getAsJsonPrimitive(java.lang.String memberName)
And then with a JsonArray, you can iterate with for (final JsonElement element : jsonArray) or .forEach, and you can get JsonElements with the JsonElement get(int i) accessor.
So, say you had your original JsonObject response and wanted to get the value of body.field1 in the second element of the body list, you might do:
String value = jsonObject
.getAsJsonArray("body")
.get(1)
.getAsJsonObject()
.getAsJsonObject("body")
.getAsJsonObject("field1");

How to keep List name using Gson

I need to get JSON response
{
"text": [
"blabla",
"blabla",
"blabla"
]
}
I have list of Strings
List<String> text = new ArrayList<String>();
text.add("blabla");
text.add("blabla");
text.add("blabla");
How can I get wright result, because my solution seems to me not the best one?
Gson gson = new GsonBuilder().setPrettyPrinting().create();
String answ = gson.toJson(text);
return "{\"text\":"+answ+"}";

You need to define text as key of a map or DTOs field name
Here is how you can do this using use Guava's ImmutableMap map
return gson.toJson(ImmutableMap.of("text", text));
Or
HashMap<String, List<String>> map = new HashMap<>();
map.put("text", text);
return gson.toJson(map);
Or
Define a DTO named Data
public class Data {
private List<String> text;
public List<String> getText() {
return text;
}
public void setText(List<String> text) {
this.text = text;
}
}
Then use :
Data data = new Data();
data.setText(text);
return gson.toJson(data);

Set SQLite data to JsonObject class without using Stringbuilder

Am retrieving information from my SQLite database to display on CardView
My SQLite database structure is SQLite DB
My class is
public class ServiceRequest{
public String reqid;
public String name;
public String branch;
public Date date;
public Date time;
public String services;
//Getter and setter
.............
.............
}
I can convert this to JSON format using
List<ServiceRequest> reqs = getAllReqs();
List<ServiceRequest> jobservList = new ArrayList<>();
for (ServiceRequest access : reqs) {
ServiceRequest ob = new ServiceRequest();
ob.setId(access.getId());
ob.setBranch(access.getBranch());
ob.setName(access.getName());
ob.setDate(access.getDate());
ob.setTime(access.getTime());
ob.setServices(access.getServices());
jobservList.add(ob);
}
Gson gson = new GsonBuilder().setPrettyPrinting().create();
String json2 = gson.toJson(jobservList);
return json2;
but my desired JSONObject format is
{
"100": {
"name": "Rahul Suresh",
"branch": "Koramangala",
"phNumber":"123456",
"date": "2016-08-06",
"time": "16:00",
"reqServices": "Loans"
},
"200": {
"name": "Sidh",
"branch": "Jayanagar",
"phNumber":"182694",
"date": "2016-08-12",
"time": "11:00",
"reqServices": "OpenAcc,SafeDeposit"
}
}
so that I will get one whole JSON object with a single call
JSONObject jb = (JSONObject) jsonObject.get(Integer.toString(id));
100,200 are 'reqid' s
It's possible to achieve this using string builder. But is there any other ways to implement this like using an object mapper along with a class or something..?

If you would like to form the JSON you have shown, you could "pull out" the ID into a HashMap key, then set the value to be your object.
I can't remember how Gson handles the conversion of the object values in the map, but this is the general idea
List<ServiceRequest> reqs = getAllReqs();
HashMap<Integer, ServiceRequest> map = new HashMap<Integer, ServiceRequest>();
for (ServiceRequest access : reqs) {
map.put(access.getId(), access);
}
Gson gson = new GsonBuilder().setPrettyPrinting().create();
String json2 = gson.toJson(map); // TODO: Not sure if this will work
return json2;

Parsing the nested JSON Array using Jackson library in java

I would like to know how to parse the following JSON using jackson library in java to construct the URI like http://api.statdns.com/google.com/cname
{
"status": {
"status": 200,
"msg": "SUCCESS"
},
"apicalls": [
{
"API": {
"method": "get",
"success": "200",
"baseURL": "http://api.statdns.com/",
"param1": "google.com/",
"param2": "cname",
"continue_on_fail": "1",
"add_header2": "'Accept', 'application/json'",
"add_header1": "'Content-Type', 'application/json'",
"client_id": "101"
},
"id": 1385
}
]
}
I have written bad code to parse the above json array. Following is the code i used,
public void parseJSON(String json) {
try{
JsonFactory factory = new JsonFactory();
JsonParser parser;
parser = factory.createJsonParser(json);
parser.setCodec(new ObjectMapper()); // to avoid IllegalStateException
JsonToken current;
current = parser.nextToken();
if (current != JsonToken.START_OBJECT) {
System.out.println("Error: root should be object: quiting.");
return;
}
while (parser.nextToken() != JsonToken.END_OBJECT) {
String fieldName = parser.getCurrentName();
// Move from field name to field value
current = parser.nextToken();
if (fieldName.equals("APIcalls")) {
JsonNode node = parser.readValueAsTree();
JsonNode currentJson = node.findValue("API");
System.out.println("Current JSON :: " + currentJson);
JsonNode url = currentJson.get("baseURL");
JsonNode param1 = currentJson.get("param1");
JsonNode param2 = currentJson.get("param2");
String baseURL = url.asText();
String params1 = param1.asText();
String params2 = param2.asText();
String uri = baseURL + params1 + params2;
System.out.println("URL :: " + uri);
initiateRESTCall(uri);
}
}
} catch (JsonParseException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
Could anyone help me to know parsing the JSON using jackson? Help is highly appreciated.

If you are using jackson library, then you should go something like this:
I am using response from http://api.statdns.com/google.com/cname
public void parseJSON(String json) {
JSONObject parse = new JSONObject(data);
if(parse.get("question") instanceof JSONObject){
JSONObject questionJson = (JSONObject) parse.get("question");
System.out.println("Name"+questionJson.getString("name"));
System.out.println("Type"+questionJson.getString("type"));
System.out.println("Class"+questionJson.getString("class"));
}
else if(parse.get("question") instanceof JSONArray){
JSONArray questionJson = (JSONArray) parse.get("question");
String[] nameAttrib=new String[questionJson.length()];
String[] typeAttrib=new String[questionJson.length()];
String[] classAttrib=new String[questionJson.length()];
for(int i=0;i<questionJson.length();i++){
JSONObject questionJsonData=(JSONObject)questionJson.get(i);
nameAttrib[i]=questionJsonData.getString("name");
typeAttrib[i]=questionJsonData.getString("type");
classAttrib[i]=questionJsonData.getString("class");
System.out.println("Name: "+nameAttrib[i]);
System.out.println("Type: "+typeAttrib[i]);
System.out.println("Class: "+classAttrib[i]);
}
}
else if (parse.get("question").equals(null)){
System.out.println("question"+null);
}
}
Here I am doing for "question" only, similarly you can do other as well say "answer", "authority" in case url you have mentioned http://api.statdns.com/google.com/cname.
Hopefully it helps you with your problem..!!!!

If you are confident in the JSON not changing, a quick and dirty way to simplify your code is to use JSON Pointers.
// prefer injecting your project's ObjectMapper
private static final ObjectMapper om = new ObjectMapper();
public void parseJSON(String json) throws IOException {
JsonNode jsonNode = om.readTree(json);
String uri = new StringBuilder(jsonNode.findValue("baseURL").asText())
.append(jsonNode.findValue("param1").asText())
.append(jsonNode.findValue("param2").asText())
.toString();
initiateRESTCall(uri);
}
This becomes vulnerable if multiple apicalls entries are returned.

I don't know JACKSON library but I think it is similar to GSON. You just have to make some POJO and the library will take care of filling the fields for you.
For instance to convert your string to MyJSONClass use the following classes :
class Status {
int status;
String msg;
}
class APIClass {
String method;
String success;
String baseURL;
String param1;
String param2;
String continue_on_fail;
String add_header2;
String add_header1;
String client_id;
}
class APICall {
APIClass API;
int id;
}
class MyJSONClass {
Status status;
List<APICall> apicalls;
}
This set of classes could be transformed to JSON with JACKSON library (thanks to this stackoverflow answer) like that:
ObjectWriter ow = new ObjectMapper().writer().withDefaultPrettyPrinter();
String json = ow.writeValueAsString(object);

Interpreting and reading JSON with GSON

I'm having trouble trying to make sense of this JSON string.
{
"results":[
{
"user":{
"gender":"female",
"name":{
"title":"miss",
"first":"taylor",
"last":"anderson"
},
"location":{
"street":"3645 dogwood ave",
"city":"roseburg",
"state":"new hampshire",
"zip":"20963"
},
"email":"taylor.anderson49#example.com",
"username":"heavyduck595",
"password":"liverpool",
"salt":"UK`o;9a_",
"md5":"6c8db0305b4591d8d9820d9f8edfd162",
"sha1":"906df4c09f3a87899666cb57bf974bd9b1950ea6",
"sha256":"3b12f5e51688578f845bef8ae1750d3e263c2010691010a80ce632a6b2323c03",
"registered":"1359027425",
"dob":"16243995",
"phone":"(934)-888-7068",
"cell":"(727)-467-8384",
"SSN":"697-20-6143",
"picture":"http://api.randomuser.me/0.3/portraits/women/30.jpg"
},
"seed":"5eaf02877746c7e",
"version":"0.3"
}
]
}
It's the first time I've really used JSON and want to try and interpret it appropriately. This is the code i have thus far:
static class Results{
String results;
}
static class User{
String gender;
String name;
String location;
List<Results> items;
}
private static String readUrl(String urlString) throws Exception {
BufferedReader reader = null;
try {
URL url = new URL(urlString);
reader = new BufferedReader(new InputStreamReader(url.openStream()));
StringBuffer buffer = new StringBuffer();
int read;
char[] chars = new char[1024];
while ((read = reader.read(chars)) != -1)
buffer.append(chars, 0, read);
return buffer.toString();
} finally {
if (reader != null)
reader.close();
}
}
public void larry() throws Exception{
String json = readUrl("http://api.randomuser.me/");
System.out.println(json);
Gson gson = new Gson();
User page = gson.fromJson(json, User.class);
System.out.println(page.name);
for (Results item : page.items)
System.out.println(" " + item.results);
}

There is nothing particularly complicated about JSON, or mapping it to your own Java classes. You just have to understand the basic structure.
Your JSON is an object that has exactly one field; results. This is what {} means:
{ "results": ... }
That field holds an array. That's the [].
{ "results": [ ... ] }
That array holds another object (presumably you'd have more than one in an array, but the JSON you've posted just has one). That object has three fields, one of which ("user") holds another object with the other two being strings.
To map that to your own classes, you simply make them look like that JSON:
class JsonResult {
List<Result> results; // JSON arrays map to Java Lists
}
class Result {
User user;
String seed;
String version;
}
class User {
String gender;
Name name;
// and so on ...
}
class Name {
String title;
String first;
String last;
}
And so forth. You build classes to match the objects (again, denoted by {}) in the JSON, and structure everything accordingly.
As #HotLicks notes in his comment, you can decide not to map to Java classes and use a "clean" parser. In fact, Gson offers this with it's JsonParser class. This will just parse the JSON to a tree from which you can extract the info you want:
JsonElement element = new JsonParser().parse(yourJsonString);
From there you can access the JSON structure using the field names:
JsonObject root = element.getAsJsonObject();
JsonArray array = root.getAsJsonArray("results");
By accessing the JSON structure you can get to whatever you want.