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Pulling out value of keys in JSON using Java, when key is under hierarchy

I need to pull out value of RecordOne from following JSON.
{
"errors": [],
"data": {
"paging": {
"RecordOne": 8,
"RecordTwo": 9,
"recordThree": 2,
"totalNumberOfRecords": 86052
},
"products": [
{
"testabstract": "test data",
"authors": "Frank Jr.",
"invertedauthors": "Frank VJr.",
"formatCode": "KND"
}
]
}
}
I'm using Java as language and JSON object to achieve the same, following is what I'm using:
protected String getTokenValueUnderHeirarchy(String responseString){
JSONObject json = new JSONObject(responseString);
String val= json.getJSONObject("data").getJSONObject("paging").getString("RecordOne");
System.out.println("val::"+val);
return val;
}
I'm getting value of val = 1, it should be 8
If I try to seek value for key totalNumberOfRecords with same code it returns correct value which is 86052
I know it's something silly but I can't catch it.

When I ran your code with the JSON example, I ended up with a "JSONException: JsonObject["RecordOne"] is not a string"..... which it isn't. Wrapping the 8 with double quotes: "8" returned the value that you expected. You can access this value with other get methods: getInt if you would like.
This test case parses both a String and an int. I pulled this from your example. Does it run for you?
package org.nadnavillus.test;
import org.json.JSONObject;
import org.junit.Test;
public class TestCase {
protected String getTokenValueUnderHeirarchy(String responseString) throws Exception {
JSONObject json = new JSONObject(responseString);
String val= json.getJSONObject("data").getJSONObject("paging").getString("RecordOne");
System.out.println("val::"+val);
return val;
}
protected String getTokenValueUnderHeirarchyInt(String responseString) throws Exception {
JSONObject json = new JSONObject(responseString);
int val= json.getJSONObject("data").getJSONObject("paging").getInt("RecordTwo");
System.out.println("val::"+val);
return String.valueOf(val);
}
#Test
public void testJson() throws Exception {
String input = "{\"errors\": [], \"data\": {\"paging\": {\"RecordOne\": \"8\", \"RecordTwo\": 9, \"recordThree\": 2, \"totalNumberOfRecords\": 86052}}}";
String test = this.getTokenValueUnderHeirarchy(input);
System.out.println(test);
test = this.getTokenValueUnderHeirarchyInt(input);
System.out.println(test);
}
}

return any exception in json in rest api

Is there any simple methods to return exception in JSON using Rest api?
I've already googled this question, but all solutions i see, was about throwing exceptions during some calculations. But what if income parameters are wrong? I mean what if there is sone string instead of int input parameter?
I created some DTO class for input data:
#XmlRootElement
public class RequestDTO implements Serializable{
private static final long serialVersionUID = 1L;
#XmlElement(name = "request_id")
private String requestId;
#XmlElement(name = "site")
private List<String> sitesIds;
#XmlElement(name = "date_begin")
#JsonSerialize(using = DateSerializer.class)
#JsonDeserialize(using = DateDeserializer.class)
private Date dateBegin;
#XmlElement(name = "date_end")
#JsonSerialize(using = JsonDateSerializer.class)
#JsonDeserialize(using = JsonDateDeserializer.class)
private Date dateEnd;
#XmlElement(name = "volume")
private double volume;
// there is getters and setters
}
If i sent something like 'qwerty' instead of 'volume' field in my json request i'l see error message like Runtime. Is it possible to handle it in someway? I mean to return error in json with such structure?
public class ExceptionDTO {
private String shortExceptionMessage;
private String stackTrace;
public ExceptionDTO(String shotExceptionMessage, String stackTrace){
this.shortExceptionMessage = shotExceptionMessage;
this.stackTrace = stackTrace;
}
public String getShortExceptionMessage() {
return shortExceptionMessage;
}
public String getStackTrace() {
return stackTrace;
}
}
UPD1:
#Provider
#Singleton
public class ExceptionMapperProvider implements ExceptionMapper<Exception>{
#Override
public Response toResponse(final Exception e) {
StringBuilder trace = new StringBuilder();
IntStream.range(0, e.getStackTrace().length)
.forEach(i -> trace.append(e.getStackTrace()[i]).append('\n'));
ExceptionDTO exceptionMessage = new ExceptionDTO(
e.toString(),
trace.toString()
);
return Response.status(500).entity(exceptionMessage).build();
}
}

As it's not really clear if you are interested on checking if field or value of the payload is correct, here are a few ways to work with both.
If you want to check if the value for a field is correct (ie volume field value should be greater than zero etc), check out bean validation. This makes use of annotations on the fields you want to verify.
// for example
#Min(value = 0, message = "invalid message")
private double range;
To use your ExceptionDTO as error response whenever one of those validation fails, you can do so by creating an ExceptionMapper<ConstraintViolationException>. check it here for more details.
If you are checking for the invalid field (ie client sends ragne fields instead of range), have a look at the stack trace on what exception is being thrown. Then register an exception mapper with your ExceptionDTO as body.
For example, if UnrecognizedPropertyException is thrown then you can add:
#Provider
public class UnrecognizedPropertyExceptionMapper implements ExceptionMapper<UnrecognizedPropertyException> {
#Override
public Response toResponse(UnrecognizedPropertyException e) {
ExceptionDTO myDTO = // build response
return Response.status(BAD_REQUEST).entity(myDTO).build();
}
}

If you want to validate input parameters in the request, you should return status code 400 (Bad Request) along with the error details. You can simply send json
{ "error": { "message": "string received for parameter x, where as int expected" } with the response status code 400.
`

I did a bit of research and determined that the best way to encode a Java exception in JSON is to use a convention developed by Oasis that looks like this:
{
"error": {
"code": "400",
"message": "main error message here",
"target": "approx what the error came from",
"details": [
{
"code": "23-098a",
"message": "Disk drive has frozen up again. It needs to be replaced",
"target": "not sure what the target is"
}
],
"innererror": {
"trace": [ ... ],
"context": [ ... ]
}
}
}
details is a list that should have an entry for each nested cause exception in the chain.
innererror.trace should include the stack trace if you wish, as a list of string values.
The response status code should be 400 unless you have a good reason for making it something else, and the code in the structure should match whatever you sent.
Write one method to convert a Java exception to this format, and you are done. Use it consistently and your JS code will be able to handle and display the exception values.
More of the details of the other approaches evaluated and dismissed are covered in this blog post on JSON REST API – Exception Handling
https://agiletribe.purplehillsbooks.com/2015/09/16/json-rest-api-exception-handling/
Here is the java method to convert an exception to this format:
public static JSONObject convertToJSON(Exception e, String context) throws Exception {
JSONObject responseBody = new JSONObject();
JSONObject errorTag = new JSONObject();
responseBody.put("error", errorTag);
errorTag.put("code", 400);
errorTag.put("target", context);
JSONArray detailList = new JSONArray();
errorTag.put("details", detailList);
String lastMessage = "";
Throwable runner = e;
while (runner!=null) {
String className = runner.getClass().getName();
String msg = runner.toString();
runner = runner.getCause();
JSONObject detailObj = new JSONObject();
detailObj.put("message",msg);
int dotPos = className.lastIndexOf(".");
if (dotPos>0) {
className = className.substring(dotPos+1);
}
detailObj.put("code",className);
System.out.println(" ERR: "+msg);
detailList.put(detailObj);
}
JSONObject innerError = new JSONObject();
errorTag.put("innerError", innerError);
JSONArray stackList = new JSONArray();
runner = e;
while (runner != null) {
for (StackTraceElement ste : runner.getStackTrace()) {
String line = ste.getFileName() + ":" + ste.getMethodName() + ":" + ste.getLineNumber();
stackList.put(line);
}
stackList.put("----------------");
runner = runner.getCause();
}
errorTag.put("stack", stackList);
return responseBody;
}

How do I make nested JSON Objects using Gson?

I have written a program that does some probability calculations and gives its results in the form of arrays. I want to convert these results to JSON format, but I am having issues.
I want my json object to look like this:
{
"totalSuggestions": 6,
"routes": {
"rank_2": {
"Source": "ABC",
"Weight": "0.719010390625",
"Destination": "XYZ"
},
"rank_1": {
"Source": "XYZ",
"Weight": "0.7411458281249999",
"Destination": "ABC"
},
"rank_0": {
"Source": "LMN",
"Weight": "0.994583325",
"Destination": "PQR"
}
}
}
What I understood is that I need to have an object class with the structure of my objects. For now I am experimenting with the rank object only but failing to form the required JSON.
My code for the object structure:
public class Object {
int rank_;
public class Inner{
String Source;
String Destination;
String Weightage;
}
}
I can pass either an instance of Object or an instance of Inner to toJson() method so I either get {"rank_":1} or {"Source":"ABC","Destination":"XYZ","Weightage":"123"}.
I cant seem to put each of the inner object to the corresponding rank object.
I did it with relative ease with org.json but that library has some issues with Android studio so I had to switch to Gson. What I did earlier (which worked as well) was:
public JSONObject convertToJson(int mkr, String[][] result){
JSONObject outerObj = new JSONObject();
JSONObject innerObj = new JSONObject();
JSONObject[] temp = new JSONObject[mkr];
outerObj.put("totalSuggestions", marker);
outerObj.put("routes",innerObj);
for (int i=0;i<marker;i++){
String[] useless = result[i][0].split("-");
temp[i]= new JSONObject();
temp[i].put("Source",useless[0] );
temp[i].put("Destination", useless[1]);
temp[i].put("Weight", result[i][1]);
innerObj.put("rank_"+i, temp[i]);
}
System.out.println(outerObj.toString());
return outerObj;
}

Well, first: related objects should probably be in a class together. So lets start with a simple class:
public class Results {
int mkr;
String[][] result;
}
Now we want to serialize it. We could construct a different data structure, or we could just write our own custom serializer. We want to have our custom class to allow us to use Gson's type inference for doing so, plus the code is just easier to understand. I will show you how to serialize the data structure, and I'll leave the deserialization as an exercise for you.
We create a TypeAdapter<Results>:
public class ResultsAdapter extends TypeAdapter<Results> {
public Results read(JsonReader reader) throws IOException {
if (reader.peek() == JsonToken.NULL) {
reader.nextNull();
return null;
}
// exercise for you
return results;
}
public void write(JsonWriter writer, Results value) throws IOException {
if (value == null) {
writer.nullValue();
return;
}
writer.beginObject();
writer.name("totalSuggestions").value(value.mkr);
writer.name("routes");
writer.beginObject();
for(int i = 0; i < value.mkr; i++) {
writer.name("rank_"+i);
writer.beginObject();
String[] sourceDestSplit = result[i][0].split("-");
writer.name("Source").value(sourceDestSplit[0]);
writer.name("Destination").value(sourceDestSplit[1]);
writer.name("Weight").value(result[i][1]);
writer.endObject();
}
writer.endObject();
writer.endObject();
}
}
You can then call this method by doing (note: should only create the Gson object once, but I did it this way to keep the code short):
public String convertToJson(Results results) {
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(new ResultsAdapter()):
Gson gson = builder.build();
return gson.toJson(results);
}
This will work you the way you've asked, but I strongly recommend using JSON's array syntax instead (using []). Try this instead:
public void write(JsonWriter writer, Results value) throws IOException {
if (value == null) {
writer.nullValue();
return;
}
writer.beginObject();
writer.name("totalSuggestions").value(value.mkr);
writer.name("routes");
writer.beginArray();
for(int i = 0; i < value.mkr; i++) {
writer.beginObject();
String[] sourceDestSplit = result[i][0].split("-");
writer.name("Source").value(sourceDestSplit[0]);
writer.name("Destination").value(sourceDestSplit[1]);
writer.name("Weight").value(result[i][1]);
writer.endObject();
}
writer.endArray();
writer.endObject();
}
Doing it this will will result in JSON that looks like this, which will be easier to deserialize on the other side and iterate through, because you won't have to dynamically generate maps for the keys.:
{
"totalSuggestions": 6,
"routes": [
{
"Source": "ABC",
"Weight": "0.719010390625",
"Destination": "XYZ"
},
{
"Source": "XYZ",
"Weight": "0.7411458281249999",
"Destination": "ABC"
},
{
"Source": "LMN",
"Weight": "0.994583325",
"Destination": "PQR"
}
]
}

I landed here while searching for a similar solution for the com.google.gson.JsonObject library. Now, I've found it:
JsonObject mainJson = new JsonObject();
JsonObject innerJson = new JsonObject();
innerJson.addProperty("#iot.id", "31");
mainJson.add("Datastream", innerJson); // <-- here the nesting happens
mainJson.addProperty("result", 12.3);
// fetch inner variable like this
System.out.println(mainJson.get("Datastream").getAsJsonObject().get("#iot.id").getAsString());
This works fine for me using the com.google.gson.JsonObject library.

For the record, this is what i did.
import java.util.*;
public class DataObject {
public int Suggestions;
HashMap<String, route> routes = new HashMap<>();
//constructor
public DataObject(int mkr, String[][] routesArr){
Suggestions = mkr;
{
for (int i=0;i<Suggestions;i++){
routes.put("rank_"+(i+1),new route(routesArr[i]));
}
}
}
//class to populate the hashmap
public class route{
public String Origin;
public String Destination;
public String Weight;
public route(String arr[]){
String[] splitter = arr[0].split("-");
this.Origin = splitter[0];
this.Destination = splitter[1];
this.Weight = arr[1];
}
}
}

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);

GSON identifying JSON Object as Primitive

I am writing a relatively simple messaging app that saves its logs in the JSON format, and I am using the GSON library to parse these. I load a JSON file from a server, and put it trough Gson.toJsonTree() function. I'm not sure this is expected, but when I test the result from the previous function with the isJsonSomething() functions (isJsonObject,isJsonAray,isJsonNull,isJsonPrimitive), isJsonPrimitive returns true, and I can't parse it into a object. This is my JSON file's contents:
{
"users": [
{
"picture": "",
"type": "user",
"name": "kroltan"
}
],
"description": "No description",
"messages": [
{
"content": "something",
"time": "2013-08-30 00:38:17.212000",
"type": "message",
"author": "someone"
}
],
"type": "channel",
"name": "default"
}
And here is the class used to parse it into POJOs: (CLEANUP comments is where I've removed irrelevant code from the post)
package com.example.testapp;
//CLEANUP: All needed imports
import com.example.testapp.data.*;
import com.google.gson.*;
public class JSONConverter {
public interface JsonTypeLoadedListener {
public void onSucess(JSONType jsonType);
public void onFailure(Exception e);
}
public static final String DATE_FORMAT = "dd-MM-yyyy HH:mm:ss.SSS";
public static final HashMap<String, Class<?>> JSON_TYPES = new HashMap<String, Class<?>>();
public JSONConverter() {
JSON_TYPES.clear();
JSON_TYPES.put("channel", Channel.class);
JSON_TYPES.put("user", User.class);
JSON_TYPES.put("message", Message.class);
}
public void loadFromURL(final URL url, final JsonTypeLoadedListener listener) {
new Thread(new Runnable() {
#Override
public void run() {
JsonObject result = null;
Gson gson = new GsonBuilder().setDateFormat(DATE_FORMAT).create();
if (url.getProtocol().equals("http")) {
try {
String content = //Loads from a server, omitted for clarity
result = gson.toJsonTree(content).getAsJsonObject();
conn.disconnect();
} catch (Exception e) {
e.printStackTrace();
listener.onFailure(e);
return;
}
} else if (url.getProtocol().equals("file")) {
try {
String content = //Loads from a file, omitted for clarity
result = gson.toJsonTree(content).getAsJsonObject();
br.close();
} catch (Exception e) {
e.printStackTrace();
listener.onFailure(e);
return;
}
}
listener.onSucess((JSONType) gson.fromJson(result, JSON_TYPES.get(result.get("type").getAsString())));
}
}, "URLLoader").start();
}
public JSONType loadFromString(String s) {
Gson gson = new Gson();
JsonObject result = gson.toJsonTree(s).getAsJsonObject();
return (JSONType) gson.fromJson(result, JSON_TYPES.get(result.get("type").getAsString()));
}
}
The classes Message, User and Channel all inherit from JSONType (a custom class with a field called type and some utility methods) and contain all values present in the above mentioned JSON file.
When it reaches gson.toJsonTree(content).getAsJsonObject(), I get this error in Logcat (string omitted for clarity, it's just the full file):
java.lang.IllegalStateException: Not a JSON Object: "String containing all the file with tabs represented as \t"

I'm guessing that the tabs are causing your issue. Try to remove them with:
content = content.replaceAll("\\s","")
this will simply clean your json string from any whitespace.
Btw I suggests you to get rid of Gson library and use directly the JSONObject provided in the android sdk. You can initialize it directly with the json string, as new JSONObject(content). :)