How to iterate over a JSONObject

Question

I use a JSON library called JSONObject  I don t mind switching if I need to     I know how to iterate over JSONArrays  but when I parse JSON data from Facebook I don t get an array  only a JSONObject  but I need to be able to access an item via its index  such as JSONObject 0  to get the first one  and I can t figure out how to do it         http   http   url com             id    http   http   url com              http   url2 co             id    http   url2 com            shares   16               http   url3 com             id    http   url3 com            shares   16

User · Answer

We used below set of code to iterate over JSONObject fields  Iterator iterator   jsonObject entrySet   iterator     while  iterator hasNext               Entry lt String  JsonElement gt  entry    Entry lt String  JsonElement gt   iterator next            processedJsonObject add entry getKey    entry getValue

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First put this somewhere   private  lt T gt  Iterable lt T gt  iteratorToIterable final Iterator lt T gt  iterator        return new Iterable lt T gt               Override         public Iterator lt T gt  iterator                 return iterator                       Or if you have access to Java8  just this   private  lt T gt  Iterable lt T gt  iteratorToIterable Iterator lt T gt  iterator        return    - gt  iterator      Then simply iterate over the object s keys and values   for  String key   iteratorToIterable object keys           JSONObject entry   object getJSONObject key

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Most of the answers here are for flat JSON structures  in case you have a JSON which might have nested JSONArrays or Nested JSONObjects  the real complexity arises  The following code snippet takes care of such a business requirement  It takes a hash map  and hierarchical JSON with both nested JSONArrays and JSONObjects and updates the JSON with the data in the hash map public void updateData JSONObject fullResponse  HashMap lt String  String gt  mapToUpdate         fullResponse keySet   forEach keyStr - gt            Object keyvalue   fullResponse get keyStr            if  keyvalue instanceof JSONArray                updateData   JSONArray  keyvalue  getJSONObject 0   mapToUpdate             else if  keyvalue instanceof JSONObject                updateData  JSONObject  keyvalue  mapToUpdate             else                  System out println  quot key   quot    keyStr    quot  value   quot    keyvalue               if  mapToUpdate containsKey keyStr                     fullResponse put keyStr  mapToUpdate get keyStr                                        You have to notice here that the return type of this is void  but sice objects are passed as refernce this change is refelected to the caller

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I made a small recursive function that goes through the entire json object and saves the key path and its value      My stored keys and values from the json object HashMap lt String String gt  myKeyValues   new HashMap lt String String gt         Used for constructing the path to the key in the json object Stack lt String gt  key path   new Stack lt String gt         Recursive function that goes through a json object and stores     its key and values in the hashmap  private void loadJson JSONObject json       Iterator lt   gt  json keys   json keys         while  json keys hasNext              String json key    String json keys next             try              key path push json key               loadJson json getJSONObject json key            catch  JSONException e                 Build the path to the key            String key                  for String sub key  key path                  key    sub key                              key   key substring 0 key length  -1               System out println key      json getString json key               key path pop               myKeyValues put key  json getString json key                        if key path size    gt  0           key path pop

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I once had a json that had ids that needed to be incremented by one since they were 0-indexed and that was breaking Mysql auto-increment   So for each object I wrote this code - might be helpful to someone   public static void  incrementValue JSONObject obj  List lt String gt  keysToIncrementValue            Set lt String gt  keys   obj keySet            for  String key   keys                Object ob   obj get key                if  keysToIncrementValue contains key                     obj put key   Integer obj get key    1                              if  ob instanceof JSONObject                    incrementValue  JSONObject  ob  keysToIncrementValue                             else if  ob instanceof JSONArray                    JSONArray arr    JSONArray  ob                  for  int i 0  i  lt  arr length    i                          Object arrObj   arr get 0                       if  arrObj instanceof JSONObject                            incrementValue  JSONObject  arrObj  keysToIncrementValue                                                                           usage   JSONObject object        incrementValue object  Arrays asList  id    product id    category id    customer id       this can be transformed to work for JSONArray as parent object too

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Below code worked fine for me  Please help me if tuning can be done  This gets all the keys even from the nested JSON objects    public static void main String args          String s          Sample JSON to be parsed      JSONParser parser   new JSONParser        JSONObject obj   null      try           obj    JSONObject  parser parse s            SuppressWarnings  unchecked           List lt String gt  parameterKeys   new ArrayList lt String gt  obj keySet             List lt String gt   result   null          List lt String gt  keys   new ArrayList lt  gt             for  String str   parameterKeys                keys add str               result   this addNestedKeys obj  keys  str                     System out println result toString           catch  ParseException e            e printStackTrace            public static List lt String gt  addNestedKeys JSONObject obj  List lt String gt  keys  String key        if  isNestedJsonAnArray obj get key              JSONArray array    JSONArray  obj get key           for  int i   0  i  lt  array length    i                  try                   JSONObject arrayObj    JSONObject  array get i                   List lt String gt  list   new ArrayList lt  gt  arrayObj keySet                     for  String s   list                        putNestedKeysToList keys  key  s                       addNestedKeys arrayObj  keys  s                                   catch  JSONException e                    LOG error     e                                 else if  isNestedJsonAnObject obj get key              JSONObject arrayObj    JSONObject  obj get key           List lt String gt  nestedKeys   new ArrayList lt  gt  arrayObj keySet             for  String s   nestedKeys                putNestedKeysToList keys  key  s               addNestedKeys arrayObj  keys  s                       return keys     private static void putNestedKeysToList List lt String gt  keys  String key  String s        if   keys contains key   Constants JSON KEY SPLITTER   s             keys add key   Constants JSON KEY SPLITTER   s              private static boolean isNestedJsonAnObject Object object        boolean bool   false      if  object instanceof JSONObject            bool   true            return bool     private static boolean isNestedJsonAnArray Object object        boolean bool   false      if  object instanceof JSONArray            bool   true            return bool

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Maybe this will help   JSONObject jsonObject   new JSONObject contents trim     Iterator lt String gt  keys   jsonObject keys     while keys hasNext          String key   keys next        if  jsonObject get key  instanceof JSONObject                 do something with jsonObject here

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org json JSONObject now has a keySet   method which returns a Set lt String gt  and can easily be looped through with a for-each    for String key   jsonObject keySet

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The simpler approach is  just found on W3Schools   let data               JSON Object for let d in data       console log d      It gives you property name     console log data d       And this gives you its value    UPDATE This approach works fine until you deal with the nested object so this approach will work  const iterateJSON    jsonObject  output         gt      for  let d in jsonObject        if  typeof jsonObject d       quot string quot           output d    jsonObject d             if  typeof jsonObject d       quot object quot           output d    iterateJSON jsonObject d                return output     And use the method like this let output   iterateJSON your json object

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With Java 8 and lambda  cleaner   JSONObject jObject   new JSONObject contents trim      jObject keys   forEachRemaining k - gt           https   docs oracle com javase 8 docs api java util Iterator html forEachRemaining-java util function Consumer-

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I made my small method to log JsonObject fields  and get some stings  See if it can be usefull  object JsonParser    val TAG    quot JsonParser quot          parse json object     param objJson     return  Map lt String  String gt      throws JSONException      Throws JSONException  class  fun parseJson objJson  Any    Map lt String  String gt        val map   HashMap lt String  String gt            If obj is a json array     if  objJson is JSONArray            for  i in 0 until objJson length                  parseJson objJson i                   else if  objJson is JSONObject            val it  Iterator lt   gt    objJson keys           while  it hasNext                  val key   it next   toString                  If you get an array             when  val jobject   objJson key                     is JSONArray - gt                        Log e TAG   quot  JSONArray   jobject quot                       parseJson jobject                                    is JSONObject - gt                        Log e TAG   quot  JSONObject   jobject quot                       parseJson jobject                                    else - gt                        Log e TAG   quot  adding to map   key  jobject quot                       map key    jobject toString                                                       return map

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for my case i found iterating the names   works well  for int i   0  i lt jobject names   length    i         Log v TAG   key       jobject names   getString i      value       jobject get jobject names   getString i

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Can t believe that there is no more simple and secured solution than using an iterator in this answers    JSONObject names    method returns a JSONArray of the JSONObject keys  so you can simply walk though it in loop  JSONObject object   new JSONObject     JSONArray keys   object names      for  int i   0  i  lt  keys length     i             String key   keys getString  i      Here s your key    String value   object getString  key      Here s your value

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This is is another working solution to the problem   public void test          Map lt String  String gt  keyValueStore   new HasMap lt  gt         Stack lt String gt  keyPath   new Stack        JSONObject json   new JSONObject  thisYourJsonObject        keyValueStore   getAllXpathAndValueFromJsonObject json  keyValueStore  keyPath       for Map Entry lt String  String gt  map   keyValueStore entrySet              System out println map getKey           map getValue                 public Map lt String  String gt  getAllXpathAndValueFromJsonObject JSONObject json  Map lt String  String gt  keyValueStore  Stack lt String gt  keyPath        Set lt String gt  jsonKeys   json keySet        for  Object keyO   jsonKeys            String key    String  keyO          keyPath push key           Object object   json get key            if  object instanceof JSONObject                getAllXpathAndValueFromJsonObject  JSONObject  object  keyValueStore  keyPath                      if  object instanceof JSONArray                doJsonArray  JSONArray  object  keyPath  keyValueStore  json  key                      if  object instanceof String    object instanceof Boolean    object equals null                 String keyStr                    for  String keySub   keyPath                    keyStr    keySub                                   keyStr   keyStr substring 0  keyStr length   - 1                keyPath pop                 keyValueStore put keyStr  json get key  toString                          if  keyPath size    gt  0            keyPath pop               return keyValueStore     public void doJsonArray JSONArray object  Stack lt String gt  keyPath  Map lt String  String gt  keyValueStore  JSONObject json          String key        JSONArray arr    JSONArray  object      for  int i   0  i  lt  arr length    i              keyPath push Integer toString i            Object obj   arr get i           if  obj instanceof JSONObject                getAllXpathAndValueFromJsonObject  JSONObject  obj  keyValueStore  keyPath                      if  obj instanceof JSONArray                doJsonArray  JSONArray  obj  keyPath  keyValueStore  json  key                      if  obj instanceof String    obj instanceof Boolean    obj equals null                 String keyStr                    for  String keySub   keyPath                    keyStr    keySub                                   keyStr   keyStr substring 0  keyStr length   - 1                keyPath pop                 keyValueStore put keyStr   json get key  toString                         if  keyPath size    gt  0            keyPath pop

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I will avoid iterator as they can add remove object during iteration  also for clean code use for loop   it will be simply clean  amp  fewer lines   Using Java 8 and Lamda  Update 4 2 2019   import org json JSONObject   public static void printJsonObject JSONObject jsonObj        jsonObj keySet   forEach keyStr - gt                Object keyvalue   jsonObj get keyStr           System out println  key     keyStr     value      keyvalue              for nested objects iteration if required           if  keyvalue instanceof JSONObject                printJsonObject  JSONObject keyvalue               Using old way  Update 4 2 2019   import org json JSONObject   public static void printJsonObject JSONObject jsonObj        for  String keyStr   jsonObj keySet              Object keyvalue   jsonObj get keyStr              Print key and value         System out println  key     keyStr     value      keyvalue              for nested objects iteration if required           if  keyvalue instanceof JSONObject                printJsonObject  JSONObject keyvalue             Original Answer  import org json simple JSONObject  public static void printJsonObject JSONObject jsonObj        for  Object key   jsonObj keySet                based on you key types         String keyStr    String key          Object keyvalue   jsonObj get keyStr              Print key and value         System out println  key     keyStr     value      keyvalue              for nested objects iteration if required         if  keyvalue instanceof JSONObject              printJsonObject  JSONObject keyvalue

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Iterator lt JSONObject gt  iterator   jsonObject values   iterator     while  iterator hasNext       jsonChildObject   iterator next         Do whatever you want with jsonChildObject     String id    String  jsonChildObject get  id

[java] How to iterate over a JSONObject?

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