I want to use financial data from yahoo in my program, it already works. I get the complete JSON content and I can display it. But now I want to extract the price as int.
public class Main {
public static void main (String[]args) throws IOException {
String sURL = "http://finance.yahoo.com/webservice/v1/symbols/googl/quote?format=json"; //just a string
// Connect to the URL using java's native library
URL url = new URL(sURL);
HttpURLConnection request = (HttpURLConnection) url.openConnection();
request.connect();
// Convert to a JSON object to print data
JsonParser jp = new JsonParser(); //from gson
JsonElement root = jp.parse(new InputStreamReader((InputStream) request.getContent())); //convert the input stream to a json element
JsonObject rootobj = root.getAsJsonObject(); //may be an array, may be an object.
System.out.print(rootobj);
}
}
EDIT
This is the JSON data from yahoo
{
"list" : {
"meta" : {
"type" : "resource-list",
"start" : 0,
"count" : 1
},
"resources" : [
{
"resource" : {
"classname" : "Quote",
"fields" : {
"name" : "Google Inc.",
"price" : "554.520020",
"symbol" : "GOOGL",
"ts" : "1432324800",
"type" : "equity",
"utctime" : "2015-05-22T20:00:00+0000",
"volume" : "1213288"
}
}
}
]
}
}
EDIT 2
I changed my code
JsonParser jp = new JsonParser(); //from gson
JsonElement root = jp.parse(new InputStreamReader((InputStream) request.getContent())); //convert the input stream to a json element
JsonObject obj = root.getAsJsonObject();
JsonObject result = obj.get("list").getAsJsonObject();
String result2 = result.get("resources").toString();
System.out.print(result2);
And now I already get this
[{"resource":{"classname":"Quote","fields":{"name":"Google Inc.","price":"554.520020","symbol":"GOOGL","ts":"1432324800","type":"equity","utctime":"2015-05-22T20:00:00+0000","volume":"1213288"}}}]
How can I get the "price" now?
EDIT 3
Ok I got it now, it works and I only get the price as double, but is this a smart way to solve this task?
// Convert to a JSON object to print data
JsonParser jp = new JsonParser(); //from gson
JsonElement root = jp.parse(new InputStreamReader((InputStream) request.getContent())); //convert the input stream to a json element
JsonObject obj = root.getAsJsonObject();
JsonObject result = obj.get("list").getAsJsonObject();
JsonArray result2 = result.get("resources").getAsJsonArray();
JsonObject result3 = result2.get(0).getAsJsonObject();
JsonObject result4 = result3.get("resource").getAsJsonObject();
JsonObject result5 = result4.get("fields").getAsJsonObject();
String result6 = result5.get("price").toString();
result6 = result6.replace("\"", "");
double value = Double.parseDouble(result6);
System.out.print(value);
you should reach "fields" object to extract "name", "price" etc.
The org.json library is easy to use. Example code below: your response as a string :
JSONObject obj1 = new JSONObject(response);
JSONArray arr = obj1.getJSONObject("list").getJSONArray("resources"); //GETS RESOURCES ARRAY
for (int i = 0; i < arr.length(); i++)
{
String resource = arr.getJSONObject(i).toString();
JSONObject obj2 = new JSONObject(resource);
String resourceObject = obj2.getJSONObject("resource").toString(); //RESOURCE OBJECT
JSONObject obj3 = new JSONObject(resourceObject);
String name = obj3.getJSONObject("fields").getString("name"); //REACHED THE FIELDS
float price = (float)obj3.getJSONObject("fields").getDouble("price");
System.out.println(name);
System.out.println(price);
}
Download : http://mvnrepository.com/artifact/org.json/json
He is already using gson.
If you want to continue using gson and know the structure before, you could create classes that stores the data.
class GoogleRequest{
private GoogleList list;
public GoogleList getList() {
return list;
}
public void setList(GoogleList list) {
this.list = list;
}
}
// class for list
class GoogleList{
private Meta meta;
private List<Resources> resources;
public List<Resources> getResources() {
return resources;
}
public void setResources(List<Resources> resources) {
this.resources = resources;
}
public Meta getMeta() {
return meta;
}
public void setMeta(Meta meta) {
this.meta = meta;
}
}
// create other classes here like the Resources class
JsonParser jp = new JsonParser(); // from gson
JsonElement root = jp.parse(new InputStreamReader((InputStream)request.getContent()));
GoogleRequest list = new Gson().fromJson(root,GoogleRequest.class);
The GoogleRequest should hold a List object and a Meta object. gson will introspect and set the properties. gson will set properties to null if they where not introspected. So you could use.
if( list.getResources() != null ){
// list is here
}else{
// do some other code and parse diffrent json
}
If you don't know if it is a array or object create different classes to handle it for you. Just parse the data with new Gson().fromJson();
Now remember that you need right properties for the job. Let's say you have this json in java
String json = "{\"price\" : \"554.520020\"}";
Then price needs to be Double or double. If you use Double you could check
if( obj.getPrice() != null ){
System.out.println( obj.getPrice().intValue() );
}
Note: you will loose precision if you cast double to int
Related
I'm trying to parse the below Json using the Gson lib in Java. When using other languages, such as C#, this JSON is parsed into an array, however it seems Gson converts this into a set of java attributes (which to be honest, makes more sense to me). Does anyone know if I can change this behaviour of the Gson lib?
{
"Outer": {
"0": {
"Attr1": 12345,
"Attr2": 67890
},
"1": {
"Attr1": 54321,
"Attr2": 09876
}
}
}
The below code demonstrates how Gson parses the array as a JsonObject. To be clear, I realise I've referenced outer as a JsonObject but I was just doing this to demonstrate the code. If I try and reference outer as an JsonArray, the code fails.
String json = "{\"Outer\": { \"0\": { \"Attr1\": 12345, \"Attr2\": 67890 }, \"1\": { \"Attr1\": 54321, \"Attr2\": 09876 }}}";
Gson gson = new GsonBuilder()
.disableHtmlEscaping()
.setLenient()
.serializeNulls()
.create();
JsonObject jo = gson.fromJson(json, JsonObject.class);
JsonObject outer = jo.getAsJsonObject("Outer");
System.out.println(outer);
System.out.println(outer.isJsonArray());
Result:
{"0":{"Attr1":12345,"Attr2":67890},"1":{"Attr1":54321,"Attr2":"09876"}}
false
//edit
I'm using this current simple Json as an example, however my application of this code will be to parse Json that's of varying and unknown shape. I therefore need Gson to automatically parse this to an array so that the isJsonArray returns true.
TL;DR: See "Using Deserializer" section at the bottom for parsing straight to array.
That JSON does not contain any arrays. An array would use the [...] JSON syntax.
Normally, a JSON object would map to a POJO, with the name in the name/value pairs mapping to a field of the POJO.
However, a JSON object can also be mapped to a Map, which is especially useful when the names are dynamic, since POJO fields are static.
Using Map
The JSON object with numeric values as names can be mapped to a Map<Integer, ?>, e.g. to parse that JSON to POJOs, do it like this:
class Root {
#SerializedName("Outer")
public Map<Integer, Outer> outer;
#Override
public String toString() {
return "Root[outer=" + this.outer + "]";
}
}
class Outer {
#SerializedName("Attr1")
public int attr1;
#SerializedName("Attr2")
public int attr2;
#Override
public String toString() {
return "Outer[attr1=" + this.attr1 + ", attr2=" + this.attr2 + "]";
}
}
Test
Gson gson = new GsonBuilder().create();
Root root;
try (BufferedReader in = Files.newBufferedReader(Paths.get("test.json"))) {
root = gson.fromJson(in, Root.class);
}
System.out.println(root);
Output
Root[outer={0=Outer[attr1=12345, attr2=67890], 1=Outer[attr1=54321, attr2=9876]}]
Get as Array
You can then add a helper method to the Root class to get that as an array:
public Outer[] getOuterAsArray() {
if (this.outer == null)
return null;
if (this.outer.isEmpty())
return new Outer[0];
int maxKey = this.outer.keySet().stream().mapToInt(Integer::intValue).max().getAsInt();
Outer[] arr = new Outer[maxKey + 1];
this.outer.forEach((k, v) -> arr[k] = v);
return arr;
}
Test
System.out.println(Arrays.toString(root.getOuterAsArray()));
Output
[Outer[attr1=12345, attr2=67890], Outer[attr1=54321, attr2=9876]]
Using Deserializer
However, it would likely be more useful if the conversion to array is done while parsing, so you need to write a JsonDeserializer and tell Gson about it using #JsonAdapter:
class Root {
#SerializedName("Outer")
#JsonAdapter(OuterArrayDeserializer.class)
public Outer[] outer;
#Override
public String toString() {
return "Root[outer=" + Arrays.toString(this.outer) + "]";
}
}
class OuterArrayDeserializer implements JsonDeserializer<Outer[]> {
#Override
public Outer[] deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
// Parse JSON array normally
if (json.isJsonArray())
return context.deserialize(json, Outer[].class);
// Parse JSON object using names as array indexes
JsonObject obj = json.getAsJsonObject();
if (obj.size() == 0)
return new Outer[0];
int maxKey = obj.keySet().stream().mapToInt(Integer::parseInt).max().getAsInt();
Outer[] arr = new Outer[maxKey + 1];
for (Entry<String, JsonElement> e : obj.entrySet())
arr[Integer.parseInt(e.getKey())] = context.deserialize(e.getValue(), Outer.class);
return arr;
}
}
Same Outer class and test code as above.
Output
Root[outer=[Outer[attr1=12345, attr2=67890], Outer[attr1=54321, attr2=9876]]]
I'll asume your JsonObject is a POJO class such like:
public Inner[] outer;
If you want an array of objects you can change your code to:
Inner[] jo = gson.fromJson(json, Inner[].class);
Jackson – Marshall String to JsonNode will be useful in your case.with following pom:-
//POM FILE
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.8</version>
</dependency>
//JAVA CODE
//read json file data to String
byte[] jsonData = Files.readAllBytes(Paths.get("employee.txt"));
//create ObjectMapper instance
ObjectMapper objectMapper = new ObjectMapper();
//read JSON like DOM Parser
JsonNode rootNode = objectMapper.readTree(jsonData);
JsonNode idNode = rootNode.path("id");
System.out.println("id = "+idNode.asInt());
JsonNode phoneNosNode = rootNode.path("phoneNumbers");
Iterator<JsonNode> elements = phoneNosNode.elements();
while(elements.hasNext()){
JsonNode phone = elements.next();
System.out.println("Phone No = "+phone.asLong());
}
You can use the JsonNode class's method findParent findValue and findPath which reduce your code as compare to another parsing library.
Please refer below code
1.To get an array of Objects (outerArray)
2.You can extract a JsonArray (outerJsonArray) containing values of inner objects in Outer (in case keys aren't significant for further use)
String json = "{\"Outer\": { \"0\": { \"Attr1\": 12345, \"Attr2\": 67890 }, \"1\": { \"Attr1\": 54321, \"Attr2\": 09876 }}}";
Gson gson = new GsonBuilder().disableHtmlEscaping().setLenient().serializeNulls().create();
JsonObject jo = gson.fromJson(json, JsonObject.class);
JsonObject outer = jo.getAsJsonObject("Outer");
Object[] outerArray = outer.entrySet().toArray();
// outerArray: [0={"Attr1":12345,"Attr2":67890}, 1={"Attr1":54321,"Attr2":"09876"}]
JsonArray outerJsonArray = new JsonArray();
outer.keySet().stream().forEach(key -> {
outerJsonArray.add(outer.get(key));
});
//jsonArray=[{"Attr1":12345,"Attr2":67890},{"Attr1":54321,"Attr2":"09876"}]
System.out.println(outer);
System.out.println(outerJsonArray.isJsonArray() + " " + outerJsonArray);
I have simple json which looks like this :
[
{
"id":"0",
"name":"Bob",
"place":"Colorado",
},
{
"id":"1",
"name":"John",
"place":"Chicago",
},
{
"id":"2",
"name":"Marry",
"place":"Miami",
}
]
What I want is using Java to create list of strings (List<String>) that contains all 'names'. I have some experience using Gson and I think about something like:
Gson gson = new Gson();
String[] stringArray= gson.fromJson(jsonString, " ".class);
The problem with this method is that I should create some POJO class which I didn`t in this case. Is it any way I can achieve it without creating separate class with this 'name' property ?
Using Jackson to parse, and Java 8 Streams API for extracting only the name field; the following may help you:
// Your string
jsonString = "[{ \"id\":\"0\", \"name\":\"Bob\", \"place\":\"Colorado\" }, { \"id\":\"1\", \"name\":\"John\", \"place\":\"Chicago\"}, { \"id\":\"2\", \"name\":\"Marry\", \"place\":\"Miami\" }]";
// using Jackson to parse
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.getTypeFactory();
List<MyInfo> myObjectList = objectMapper.readValue(jsonString, typeFactory.constructCollectionType(List.class, MyInfo.class));
// Java 8 Collections
List<String> nameList = myObjectList.stream().map(MyInfo::getName).collect(Collectors.toList());
Beware, it implies the usage of a MyInfo class representing your a Java class in which Json objects of yours would fit in.
You can use JSONArray to get value from key 'name'. Like this:
JSONArray jSONArray = new JSONArray(yourJson);
List<String> list = new ArrayList<>();
for (int i = 0; i < jSONArray.length(); i++) {
JSONObject object = (JSONObject) jSONArray.get(i);
String value = object.getString("name");
System.out.println(value);
list.add(value);
}
You may try the following code snippet,
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
List<String> ls = new ArrayList<String>();
JSONObject jsonObj = new JSONObject();
JSONArray jsonArr = new JSONArray();
JSONParser jsonParse = new JSONParser();
String str = "[{\"id\": \"0\",\"name\": \"Bob\",\"place\": \"Colorado\"},"
+ "{\"id\": \"1\",\"name\": \"John\",\"place\": \"Chicago\"},"
+ "{\"id\": \"2\",\"name\": \"Marry\",\"place\": \"Miami\"}]";
try {
jsonArr= (JSONArray) jsonParse.parse(str); //parsing the JSONArray
if(jsonArr!=null){
int arrayLength =jsonArr.size(); //size is 3 here
for(int i=0;i<arrayLength;i++){
jsonObj = (JSONObject) jsonParse.parse(jsonArr.get(i).toString());
ls.add(jsonObj.get("name").toString()); //as we need only value of name into the list
}
System.out.println(ls);
}
} catch (ParseException e) {
e.printStackTrace();
}catch(Exception e1){
e1.printStackTrace();
}
As you have array, use JSONArray and used jsonParse to avoid any parsing error.
I have used json-simple API to acheive the above.
So I get place_id by storing it in a Hashmap with the "name" of the place as the key.
private HashMap<String, String> placeTitleId = new HashMap<>();
if (!place.isNull("place_id")) {
placeId = place.getString("place_id");
placeTitleId.put(name, placeId);
}
Later, I create the Places Detail search url:
private String createPlaceDetailsUrl(String placeId) {
StringBuilder stringBuilder = new StringBuilder("https://maps.googleapis.com/maps/api/place/details/json?");
stringBuilder.append("placeid=").append(placeId);
stringBuilder.append("&key=").append(GOOGLE_PLACES_API_KEY);
return stringBuilder.toString();
}
Finally, I parse the json response:
JSONObject data = new JSONObject(result);
if (data.getString("status").equalsIgnoreCase("OK")) {
JSONArray photoArray = data.getJSONArray("photos");
}
What I don't understand is why the "photos" json array has no value
Android Monitor: W/System.err: org.json.JSONException: No value for photos
The documentation says that the photos[] jsonarray should have up to 10 photos. However, the json output schema does not contain a photos[] object, which I find weird. Is there a problem with how I am obtaining place_id or parsing the response?
EDIT:
The "result" String is incredibly long, but I can provide a gist:
result {
"address components" : [
*bunch of stuff*
]
...
"geometry" : {
*bunch of stuff*
}
"icon"
"id"
"photos" : [
{
"height"
"html_attributions:
"photo_reference!!
}
{
...
"photo_reference!!
}
*bunch more of these*
]
}
EDIT:
Fix is getting json object "result
JSONObject jsonObject = new JSONObject(result);
JSONObject data = new JSONObject("result");
The data object has "pictures"
Try this.
JSONObject data = new JSONObject(result);
// add log here ,make sure you have photos in your result
Log.e("result", result + "");
if (data.getString("status").equalsIgnoreCase("OK")) {
// edited here
JSONArray photoArray = data.optJSONArray("photos");
}
Edit
if (data .has("photos")) {
Log.e("photos", "photos exists");
} else {
Log.e("photos", "photos not exists");
}
Use data .has("photos") in your code and judge it .
Note
Use
JSONObject data = new JSONObject(result);
if(data.has("TAG")){
// if has it in your data,do something
}
to determine whether this tag is present in the data
I am trying retrieving the following JSON data from imagga's image recognition API.
{"results":[{"image":"http://docs.imagga.com/static/images/docs/sample/japan-605234_1280.jpg","tagging_id":null,"tags":[{"confidence":63.346307851163395,"tag":"valley"},{"confidence":60.66263009377379,"tag":"mountain"},{"confidence":44.39096006516168,"tag":"canyon"},{"confidence":42.08210930346856,"tag":"landscape"},{"confidence":33.52198895357515,"tag":"geological formation"},{"confidence":32.702112467737216,"tag":"mountains"},{"confidence":28.626223994488203,"tag":"glacier"},{"confidence":28.36,"tag":"natural depression"},{"confidence":28.03481906795487,"tag":"ravine"},{"confidence":27.269738461024804,"tag":"sky"},{"confidence":26.130797131953397,"tag":"rock"},{"confidence":23.11898739400327,"tag":"travel"},{"confidence":21.75182989551758,"tag":"alp"},{"confidence":20.956625061326214,"tag":"national"},{"confidence":20.15360199670358,"tag":"park"},{"confidence":19.826365024393702,"tag":"stone"},{"confidence":19.717420656127437,"tag":"water"},{"confidence":18.049071926896588,"tag":"river"},{"confidence":17.81629840041474,"tag":"hill"},{"confidence":17.30594970410163,"tag":"tourism"},{"confidence":17.192663177192692,"tag":"clouds"},{"confidence":16.53588724897844,"tag":"scenic"},{"confidence":15.98967256769248,"tag":"peak"},{"confidence":15.792599629554461,"tag":"lake"},{"confidence":15.532788988165363,"tag":"scenery"},{"confidence":15.453814687301834,"tag":"snow"},{"confidence":15.232632664896412,"tag":"outdoors"},{"confidence":15.212304004139495,"tag":"range"},{"confidence":15.042325772263556,"tag":"hiking"},{"confidence":14.958759294889424,"tag":"tree"},{"confidence":14.78842712696222,"tag":"forest"},{"confidence":12.853490785491731,"tag":"grass"},{"confidence":12.242518977753525,"tag":"desert"},{"confidence":12.095999999999998,"tag":"natural elevation"},{"confidence":12.03899501602295,"tag":"america"},{"confidence":11.49381779097963,"tag":"environment"},{"confidence":11.250534926394025,"tag":"usa"},{"confidence":10.935999552280517,"tag":"panorama"},{"confidence":10.838870815021957,"tag":"trees"},{"confidence":10.77081532273937,"tag":"south"},{"confidence":10.385222667460749,"tag":"summer"},{"confidence":9.967993711501377,"tag":"cloud"},{"confidence":9.960797892906747,"tag":"wild"},{"confidence":9.840206836878211,"tag":"natural"},{"confidence":9.64736797817423,"tag":"geology"},{"confidence":9.622992778171428,"tag":"rocky"},{"confidence":9.5011692563878,"tag":"outdoor"},{"confidence":9.36921935993258,"tag":"wilderness"},{"confidence":9.360136841263397,"tag":"vacation"},{"confidence":9.295849004816608,"tag":"rocks"},{"confidence":9.200756690906687,"tag":"high"},{"confidence":9.098263071652019,"tag":"highland"},{"confidence":8.912795414022,"tag":"tourist"},{"confidence":8.871604649828521,"tag":"hike"},{"confidence":8.849249986309006,"tag":"landmark"},{"confidence":8.696713373486205,"tag":"cliff"},{"confidence":8.600291951670297,"tag":"scene"},{"confidence":8.535889495009538,"tag":"stream"},{"confidence":8.530021520404471,"tag":"sunny"},{"confidence":8.255077489679804,"tag":"altitude"},{"confidence":8.016191292928964,"tag":"trail"},{"confidence":7.9938748285500605,"tag":"autumn"},{"confidence":7.985278417869093,"tag":"california"},{"confidence":7.927492176055299,"tag":"spain"},{"confidence":7.774043777890904,"tag":"adventure"},{"confidence":7.560207874392119,"tag":"peaceful"},{"confidence":7.485827508554503,"tag":"fall"},{"confidence":7.283862421876644,"tag":"erosion"},{"confidence":7.272123549182718,"tag":"terrain"},{"confidence":7.24510515635207,"tag":"rural"},{"confidence":7.234934522337296,"tag":"vista"},{"confidence":7.092282542389207,"tag":"holiday"}]}]}
I am using http://www.java2s.com/Code/Jar/o/Downloadorgjson20130603jar.htm library.
My Java code is as follows:
String imageUrl = "http://docs.imagga.com/static/images/docs/sample/japan-605234_1280.jpg",
apiKey = "",
apiSecret = "";
// These code snippets use an open-source library. http://unirest.io/java
HttpResponse response = Unirest.get("https://api.imagga.com/v1/tagging")
.queryString("url", imageUrl)
.basicAuth(apiKey, apiSecret)
.header("Accept", "application/json")
.asJson();
String js = response.getBody().toString();
System.out.println(js.toString());
JSONObject jObject = new JSONObject(response.getBody()); // json
System.out.print("hello");
JSONObject data1 = jObject.getJSONObject("results"); // get data
System.out.print(data1); // object
String projectname = data1.getString("tags"); // get the name
// from data.
System.out.print(projectname);
I am getting the error that
Exception in thread "main" org.json.JSONException:
JSONObject["results"] not found.
What I want to get is the list of "tag" and "confidence".
try this
JSONArray data1 = jObject.getJSONArray("results");
Edited Answer
String js = response.getBody().toString();
System.out.println(js.toString());
JSONObject jObject = new JSONObject(js); // json
System.out.print("hello");
JSONArray data1 = jObject.getJSONArray("results");
for(int i = 0; i < data1.length; i++)
{
JSONObject jsonObject = data1.getJSONObject(i);
String projectn ame = jsonObject.getString("tagging_id");
System.out.print(projectname);
JSONArray tagArray = jsonObject.getJsonArray("tags");
for(int j = 0; j < tagArray.length; j++)
{
JSONObject tagObject = tagArray.getJSON(j);
System.out.println("Tag == " + tagObject.getString("tag"));
}
}
To make your life more easy I'd go to model the Objects as POJO's and let Jackson's Objectmapper do the magic.
See http://wiki.fasterxml.com/JacksonDataBinding
I suppose you should try jObject.getJSONArray("results") instead of jObject.getJSONObject("results").
There is also a good tool to convert json to java: http://json2java.azurewebsites.net/
If you use it, you will see:
...other code...
public class RootObject
{
private ArrayList<Result> results;
public ArrayList<Result> getResults() { return this.results; }
public void setResults(ArrayList<Result> results) { this.results = results; }
}
...other code...
And results is list here, so use getJSONArray instead of getJSONObject
If you look into your json results has an array in it and therefore you should use getJSONArray and not getJSONObject.
JSONArray data1 = jObject.getJSONArray("results");
This question already has answers here:
How to parse JSON in Java
(36 answers)
Closed 4 years ago.
I have JSON object as follows:
member = "{interests : [{interestKey:Dogs}, {interestKey:Cats}]}";
In Java I want to parse the above json object and store the values in an arraylist.
I am seeking some code through which I can achieve this.
I'm assuming you want to store the interestKeys in a list.
Using the org.json library:
JSONObject obj = new JSONObject("{interests : [{interestKey:Dogs}, {interestKey:Cats}]}");
List<String> list = new ArrayList<String>();
JSONArray array = obj.getJSONArray("interests");
for(int i = 0 ; i < array.length() ; i++){
list.add(array.getJSONObject(i).getString("interestKey"));
}
public class JsonParsing {
public static Properties properties = null;
public static JSONObject jsonObject = null;
static {
properties = new Properties();
}
public static void main(String[] args) {
try {
JSONParser jsonParser = new JSONParser();
File file = new File("src/main/java/read.json");
Object object = jsonParser.parse(new FileReader(file));
jsonObject = (JSONObject) object;
parseJson(jsonObject);
} catch (Exception ex) {
ex.printStackTrace();
}
}
public static void getArray(Object object2) throws ParseException {
JSONArray jsonArr = (JSONArray) object2;
for (int k = 0; k < jsonArr.size(); k++) {
if (jsonArr.get(k) instanceof JSONObject) {
parseJson((JSONObject) jsonArr.get(k));
} else {
System.out.println(jsonArr.get(k));
}
}
}
public static void parseJson(JSONObject jsonObject) throws ParseException {
Set<Object> set = jsonObject.keySet();
Iterator<Object> iterator = set.iterator();
while (iterator.hasNext()) {
Object obj = iterator.next();
if (jsonObject.get(obj) instanceof JSONArray) {
System.out.println(obj.toString());
getArray(jsonObject.get(obj));
} else {
if (jsonObject.get(obj) instanceof JSONObject) {
parseJson((JSONObject) jsonObject.get(obj));
} else {
System.out.println(obj.toString() + "\t"
+ jsonObject.get(obj));
}
}
}
}}
Thank you so much to #Code in another answer. I can read any JSON file thanks to your code. Now, I'm trying to organize all the elements by levels, for could use them!
I was working with Android reading a JSON from an URL and the only I had to change was the lines
Set<Object> set = jsonObject.keySet();
Iterator<Object> iterator = set.iterator();
for
Iterator<?> iterator = jsonObject.keys();
I share my implementation, to help someone:
public void parseJson(JSONObject jsonObject) throws ParseException, JSONException {
Iterator<?> iterator = jsonObject.keys();
while (iterator.hasNext()) {
String obj = iterator.next().toString();
if (jsonObject.get(obj) instanceof JSONArray) {
//Toast.makeText(MainActivity.this, "Objeto: JSONArray", Toast.LENGTH_SHORT).show();
//System.out.println(obj.toString());
TextView txtView = new TextView(this);
txtView.setText(obj.toString());
layoutIzq.addView(txtView);
getArray(jsonObject.get(obj));
} else {
if (jsonObject.get(obj) instanceof JSONObject) {
//Toast.makeText(MainActivity.this, "Objeto: JSONObject", Toast.LENGTH_SHORT).show();
parseJson((JSONObject) jsonObject.get(obj));
} else {
//Toast.makeText(MainActivity.this, "Objeto: Value", Toast.LENGTH_SHORT).show();
//System.out.println(obj.toString() + "\t"+ jsonObject.get(obj));
TextView txtView = new TextView(this);
txtView.setText(obj.toString() + "\t"+ jsonObject.get(obj));
layoutIzq.addView(txtView);
}
}
}
}
1.) Create an arraylist of appropriate type, in this case i.e String
2.) Create a JSONObject while passing your string to JSONObject constructor as input
As JSONObject notation is represented by braces i.e {}
Where as JSONArray notation is represented by square brackets i.e []
3.) Retrieve JSONArray from JSONObject (created at 2nd step) using "interests" as index.
4.) Traverse JASONArray using loops upto the length of array provided by length() function
5.) Retrieve your JSONObjects from JSONArray using getJSONObject(index) function
6.) Fetch the data from JSONObject using index '"interestKey"'.
Note : JSON parsing uses the escape sequence for special nested characters if the json response (usually from other JSON response APIs) contains quotes (") like this
`"{"key":"value"}"`
should be like this
`"{\"key\":\"value\"}"`
so you can use JSONParser to achieve escaped sequence format for safety as
JSONParser parser = new JSONParser();
JSONObject json = (JSONObject) parser.parse(inputString);
Code :
JSONParser parser = new JSONParser();
String response = "{interests : [{interestKey:Dogs}, {interestKey:Cats}]}";
JSONObject jsonObj = (JSONObject) parser.parse(response);
or
JSONObject jsonObj = new JSONObject("{interests : [{interestKey:Dogs}, {interestKey:Cats}]}");
List<String> interestList = new ArrayList<String>();
JSONArray jsonArray = jsonObj.getJSONArray("interests");
for(int i = 0 ; i < jsonArray.length() ; i++){
interestList.add(jsonArray.getJSONObject(i).optString("interestKey"));
}
Note : Sometime you may see some exceptions when the values are not available in appropriate type or is there is no mapping key so in those cases when you are not sure about the presence of value so use optString, optInt, optBoolean etc which will simply return the default value if it is not present and even try to convert value to int if it is of string type and vice-versa so Simply No null or NumberFormat exceptions at all in case of missing key or value
From docs
Get an optional string associated with a key. It returns the
defaultValue if there is no such key.
public String optString(String key, String defaultValue) {
String missingKeyValue = json_data.optString("status","N/A");
// note there is no such key as "status" in response
// will return "N/A" if no key found
or To get empty string i.e "" if no key found then simply use
String missingKeyValue = json_data.optString("status");
// will return "" if no key found where "" is an empty string
Further reference to study
How to convert String to JSONObject in Java
Convert one array list item into multiple Items
There are many JSON libraries available in Java.
The most notorious ones are: Jackson, GSON, Genson, FastJson and org.json.
There are typically three things one should look at for choosing any library:
Performance
Ease of use (code is simple to write and legible) - that goes with features.
For mobile apps: dependency/jar size
Specifically for JSON libraries (and any serialization/deserialization libs), databinding is also usually of interest as it removes the need of writing boiler-plate code to pack/unpack the data.
For 1, see this benchmark: https://github.com/fabienrenaud/java-json-benchmark I did using JMH which compares (jackson, gson, genson, fastjson, org.json, jsonp) performance of serializers and deserializers using stream and databind APIs.
For 2, you can find numerous examples on the Internet. The benchmark above can also be used as a source of examples...
Quick takeaway of the benchmark: Jackson performs 5 to 6 times better than org.json and more than twice better than GSON.
For your particular example, the following code decodes your json with jackson:
public class MyObj {
private List<Interest> interests;
static final class Interest {
private String interestKey;
}
private static final ObjectMapper MAPPER = new ObjectMapper();
public static void main(String[] args) throws IOException {
MyObj o = JACKSON.readValue("{\"interests\": [{\"interestKey\": \"Dogs\"}, {\"interestKey\": \"Cats\" }]}", MyObj.class);
}
}
Let me know if you have any questions.