Develop Reference

JSON array parsing with Java [duplicate]

I am building an android app that needs to download and synchronise with an online database, I am sending my query from the app to a php page which returns the relevant rows from a database in JSON format.
can someone please tell me the best way to iterate through a JSON array?
I receive an array of objects:
[{json object},{json object},{json object}]
What is the simplest piece of code I could use to access the JSONObjects in the array?
EDIT: now that I think of it the method I used to iterate the loop was:
for (String row: json){
id = row.getInt("id");
name = row.getString("name");
password = row.getString("password");
}
So I guess I had was somehow able to turn the returned Json into and iterable array. Any Ideas how I could achieve this?
I apologise for my vaguness but I had this working from an example I found on the web and have since been unable to find it.

I think this code is short and clear:
int id;
String name;
JSONArray array = new JSONArray(string_of_json_array);
for (int i = 0; i < array.length(); i++) {
JSONObject row = array.getJSONObject(i);
id = row.getInt("id");
name = row.getString("name");
}
Is that what you were looking for?

I have done it two different ways,
1.) make a Map
HashMap<String, String> applicationSettings = new HashMap<String,String>();
for(int i=0; i<settings.length(); i++){
String value = settings.getJSONObject(i).getString("value");
String name = settings.getJSONObject(i).getString("name");
applicationSettings.put(name, value);
}
2.) make a JSONArray of names
JSONArray names = json.names();
JSONArray values = json.toJSONArray(names);
for(int i=0; i<values.length(); i++){
if (names.getString(i).equals("description")){
setDescription(values.getString(i));
}
else if (names.getString(i).equals("expiryDate")){
String dateString = values.getString(i);
setExpiryDate(stringToDateHelper(dateString));
}
else if (names.getString(i).equals("id")){
setId(values.getLong(i));
}
else if (names.getString(i).equals("offerCode")){
setOfferCode(values.getString(i));
}
else if (names.getString(i).equals("startDate")){
String dateString = values.getString(i);
setStartDate(stringToDateHelper(dateString));
}
else if (names.getString(i).equals("title")){
setTitle(values.getString(i));
}
}

Unfortunately , JSONArray doesn't support foreach statements, like:
for(JSONObject someObj : someJsonArray) {
// do something about someObj
....
....
}

When I tried #vipw's suggestion, I was faced with this exception:
The method getJSONObject(int) is undefined for the type JSONArray
This worked for me instead:
int myJsonArraySize = myJsonArray.size();
for (int i = 0; i < myJsonArraySize; i++) {
JSONObject myJsonObject = (JSONObject) myJsonArray.get(i);
// Do whatever you have to do to myJsonObject...
}

If you're using the JSON.org Java implementation, which is open source, you can just make JSONArray implement the Iterable interface and add the following method to the class:
#Override
public Iterator iterator() {
return this.myArrayList.iterator();
}
This will make all instances of JSONArray iterable, meaning that the for (Object foo : bar) syntax will now work with it (note that foo has to be an Object, because JSONArrays do not have a declared type). All this works because the JSONArray class is backed by a simple ArrayList, which is already iterable. I imagine that other open source implementations would be just as easy to change.

On Arrays, look for:
JSONArray menuitemArray = popupObject.getJSONArray("menuitem");

You are using the same Cast object for every entry.
On each iteration you just changed the same object instead creating a new one.
This code should fix it:
JSONArray jCastArr = jObj.getJSONArray("abridged_cast");
ArrayList<Cast> castList= new ArrayList<Cast>();
for (int i=0; i < jCastArr.length(); i++) {
Cast person = new Cast(); // create a new object here
JSONObject jpersonObj = jCastArr.getJSONObject(i);
person.castId = (String) jpersonObj.getString("id");
person.castFullName = (String) jpersonObj.getString("name");
castList.add(person);
}
details.castList = castList;

While iterating over a JSON array (org.json.JSONArray, built into Android), watch out for null objects; for example, you may get "null" instead of a null string.
A check may look like:
s[i] = array.isNull(i) ? null : array.getString(i);

null replace into string in hiberante

I have below string output :
["Kolkata","data can be, null",null,"05/31/2020",null]
but I want to have the output like below format in Java
["Kolkata","data can be, null","","05/31/2020",""]
please help me .
I am converting object to json data . Please see the below codes
List<String> test = new ArrayList<>();
List<Object[]> data =query.list();
for (int i = 0; i < data.size(); i++) {
Object[] row = (Object[]) data.get(i);
String jsonString = gson.toJson(row);
test.add(jsonString);
}
I want to apply this on jsonString variable using java 7 as not using java 8

Gson doesn't allow you to change the serialized form of strings.
Probably better to change your objects -> replace null by empty string before serialization.

You can replace every null value with an empty string inside the array using another for loop. Here is an example that will do the same.
Object[] row = new Object[]{"Kolkata","data can be, null",null,"05/31/2020",null};
for (int i = 0; i < row.length; i++) {
if (row[i] == null) {
row[i] = "";
}
}

How to loop through json arrays nested inside json objects

I have this json text which has some symptoms associated with head diseases:
{
"Head": {
"Agitation": {
"conditions": "Generalized anxiety disorder,Medication reaction or side-effect"
},
"Anxiety": {
"conditions": "Generalized anxiety disorder,Depression (Adult)"
},
"Apathy": {
"conditions": "Depression (Adult),Medication reaction or side-effect,Dementia in head injury"
}
}
}
What I want is to access and display every symptom in this Head block using a for loop, and then access each symptom's conditions and store them separately as arrays.
This java code works but it's functionality is limited:
JSONObject jsonObject = (JSONObject) object;
JSONObject bodyPart = (JSONObject) jsonObject.get("Head");
JSONObject symptoms = (JSONObject) name.get("Agitation");
String res = (String) symptoms.get("conditions");
String[] tokens = res.split(",");
for (int i = 0; i < tokens.length; i++){
System.out.println(tokens[i]);}
Instead of displaying just the conditions of Agitation, how can I display every condition associated with every symptom without having to pass their String values manually into the get methods?
I don't know if I should use JSONArray for "Head" instead of JSONObject to access the symptoms.

Assuming this is the org.json package, you can use JSONObject's keys() method to get an iterator over the object's keys.
Iterator bodyParts = jsonObject.keys();
while (bodyParts.hasNext()){
String bodyPart = (String) bodyParts.next();
JSONObject symptomsJson = jsonObject.getJSONObject(bodyPart);
Iterator symptoms = symptomsJson.keys();
// And so on...
}

My friend, if you're using java, use objects, no plain text, my recommendation is to use Json.simple,
That way you can have List of objects and use the properties you want, take a look on the link examples.

Remove object from json response Android

Hello guys I need your help. How do I remove this from my json response?
[
{
"Woa": [
"Seo",
"Rikjeo",
"JDa"
]
},
"Aha",
"Aad",
"Char"
]
I want to remove this:
{
"Woa": [
"Seo",
"Rikjeo",
"JDa"
]
}
This is what I tried so far:
for (int i = 0; i < array.length(); ++i) {
list.add(array.getString(i));
}
list.remove(0);
But it is still not removed. How do I do that? Any ideas will be greatly appreciated
Edited list.remove(1) to (0)

After removing the item you need to create the JSON again using the list.
list.remove(1);
JSONArray jsArray = new JSONArray(list);
If you want to convert JSONArray to JSON string:
jsArray.toString()

Your list will be updated, not your JSON object.
Why don't you use a JSONparser.
JSONObject obj = new JSONObject(mystring);
obj.remove("entryname");

One problem is that the element you are trying to remove is the first one, and the index of the first element of a JSONArray object is zero.
You are calling list.remove(1) which removes the second element of the array.
The following should be sufficient:
list.remove(0);
... without the stuff prior to it.
If this is not working, then my guess is that you are removing the element too late; i.e. after the JSONArray object has been serialized. However, we need to see more (relevant) code to be sure.
The Android documentation for JSONArray fails to mention that array indexing is zero-based. However, it is. I checked the source code. Furthermore most other Java data structures (arrays, lists etcetera) use zero-based indexing. (A notable exception is Java data structures modelled on the W3C DOM APIs.)

You should make something that's more general so you don't have to modify your code EVERY time the JSON changes. For example:
//here we create the JSONArray object from the string that contains the json data
JSONArray array = new JSONArray(myJsonString);
//here we create a list that represents the final result - a list of Strings
List<String> list = new ArrayList<>();
//here we parse every object that the JSONArray contains
for (int i = 0; i < array.length(); i++) {
//if the current item is an JSONObject, then we don't need it, so we continue our iteration
//this check is not necessary because of the below check,
//but it helps you see things clearly: we IGNORE JSONObjects from the array
if (array.get(i) instanceof JSONObject) {
continue;
}
//if our current object is a String, we add it to our final result
if (array.get(i) instanceof String) {
list.add(array.getString(i));
}
}

you can parse your string to JSONArray, the first element of the array is what you want.
#Test
public void test() {
String str = "[ {\"Woa\": [\"Seo\",\"Rikjeo\",\"JDa\"]},\"Aha\",\"Aad\",\"Char\"]";
try {
JSONArray array;
array = new JSONArray(str);
System.out.println(array);
System.out.println(array.get(0));
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
[{"Woa":["Seo","Rikjeo","JDa"]},"Aha","Aad","Char"]
{"Woa":["Seo","Rikjeo","JDa"]}
PASSED: test

You Can one by one remove
while (user_data.length() > 0) {
user_data.remove(user_data.keys().next());
}

JSON Array Problem

Hy!
I have a JSON Array with the tv channels and the lenght of the array is three, but after transmitting into a treemap the Value is only one.
Please Help
Code:
try
{
JSONObject menuobj = this.getJSONObject("responseData");
Log.e("XXX", menuobj.toString());
JSONArray array = menuobj.getJSONArray("countries");
TreeMap<String, Integer> map = new TreeMap<String, Integer>();
for (int i = 0; i < array.length(); i++)
{
JSONObject obj = new JSONObject();
obj = array.getJSONObject(i);
if (obj.getString("name").equals(country))
{
Log.e("XXX2", obj.toString());
JSONArray arr = obj.getJSONArray("channels");
Log.e("XXX3", String.valueOf(arr.length()));
for (int j = 0; j < arr.length(); j++)
{
JSONObject obj2 = new JSONObject();
obj2 = arr.getJSONObject(i);
map.put(obj2.getString("name"), obj2.getInt("id"));
}
Log.e("XXX4", String.valueOf(map.size()));
return map;
}
}
LogCat:
02-01 18:24:20.277: ERROR/XXX(3784): {"countries":[{"id":"1","channels":[{"id":"3","name":"ARD"},{"id":"1","name":"ORF 1"},{"id":"2","name":"ORF 2"}],"name":"Ã?sterreich"},{"id":"2","channels":[{"id":"3","name":"ARD"}],"name":"Deutschland"}]}
02-01 18:24:20.288: ERROR/XXX2(3784): {"id":"1","channels":[{"id":"3","name":"ARD"},{"id":"1","name":"ORF 1"},{"id":"2","name":"ORF 2"}],"name":"Ã?sterreich"}
02-01 18:24:20.297: ERROR/XXX3(3784): 3
02-01 18:24:20.307: ERROR/XXX4(3784): 1

I believe :
obj2 = arr.getJSONObject(i);
should be
obj2 = arr.getJSONObject(j);
So you are putting three times the same object pair of key/value to the map.

You need to use JSONArray without JSONObject:
JSONArray resultJson = new JSONArray(responseDataString);

You're missing an important logging detail, call it XXX3.5. It's almost certainly the case that the map contains one element because each call to map.put() is passing in a key that is considered equal to the key already inside the map.
Now I'd expect these keys to be the String names of the channels, which are distinct, so clearly this expectation isn't holding. Adding a log message of obj2.getString("name") (or alternatively setting a breakpoint there), will let you see what the map keys actually are, and why subsequent calls are overwriting the existing mapping. Outputting the actual class of the object would be useful too, in order to distinguish between an actual String and some class that merely contains a String.
If the elements look sensible, the problem could be a loose definition of equals() on the class in question, which equates elements that ought to seem distinct. In any case, better logging will show why
arr.getJSONObject(0).getString("name").equals(arr.getJSONObject(1).getString("name")
returns true when you expect this to return false.