How to check if a json key exists

Question

So  I get some JSON values from the server but I don t know if there will be a particular field or not   So like      regatta name   ProbaRegatta      country   Congo      status   invited      And sometimes  there will be an extra field like      regatta name   ProbaRegatta      country   Congo      status   invited      club   somevalue      I would like to check if the field named  club  exists so that at parsing I won t get org json JSONException  No value for club

User · Answer

I used hasOwnProperty  club    var myobj      regatta name   ProbaRegatta        country   Congo        status   invited        if   myobj hasOwnProperty  club            do something with club  will be false with above data       var data   myobj club   if   myobj hasOwnProperty  status            do something with the status field   will be true with above          var data   myobj status    works in all current browsers

User · Answer

Try this  if  jsonObj isNull  club         jsonObj getString  club

User · Answer

A better way  instead of using a conditional like   if  json has  club          String club   json getString  club          is to simply use the existing method optString    like this   String club   json optString  club     the optString  key   method will return an empty String if the key does not exist and won t  therefore  throw you an exception

User · Answer

just before read key check it like before read  JSONObject json obj new JSONObject yourjsonstr   if  json obj isNull  club          it s contain value to be read operation   else       it s not contain key club or isnull so do this operation here     isNull function definition   Returns true if this object has no mapping for name or if it has a mapping whose value is NULL     official documentation below link for isNull function  http   developer android com reference org json JSONObject html isNull java lang String

User · Answer

I am just adding another thing  In case you just want to check whether anything is created in JSONObject or not you can use length    because by default when JSONObject is initialized and no key is inserted  it just has empty braces    and using has String key  doesn t make any sense   So you can directly write if  jsonObject length    gt  0  and do your things   Happy learning

User · Answer

Try this   let json yourJson  if json hasOwnProperty yourKey        value json yourKey

User · Answer

you could JSONObject has  providing the key as input and check if the method returns true or false  You could also  use optString instead of getString      Returns the value mapped by name if it exists  coercing it if   necessary  Returns the empty string if no such mapping exists

User · Answer

Json has a method called containsKey      You can use it to check if a certain key is contained in the Json set    File jsonInputFile   new File  jsonFile json     InputStream is   new FileInputStream jsonInputFile   JsonReader reader   Json createReader is   JsonObject frameObj   reader readObject    reader close     if frameObj containsKey  person             Do stuff

User · Answer

You can check this way where  HAS  - Returns true if this object has a mapping for name  The mapping may be NULL   if  json has  status         String status   json getString  status        if  json has  club         String club   json getString  club            You can also check using  isNull  - Returns true if this object has no   mapping for name or if it has a mapping whose value is NULL    if   json isNull  club        String club   json getString  club

User · Answer

You can try this to check wether the key exists or not   JSONObject object   new JSONObject jsonfile   if  object containskey  key        object get  key        etc  etc

User · Answer

JSONObject class has a method named  has    http   developer android com reference org json JSONObject html has java lang String      Returns true if this object has a mapping for name  The mapping may be NULL

User · Answer

You can use the JsonNode hasNonNull String fieldName   it mix the has method and the verification if it is a null value or not

User · Answer

You can use has  public boolean has String key    Determine if the JSONObject contains a specific key   Example  JSONObject JsonObj   new JSONObject Your API STRING     JSONObject is an unordered collection of name value pairs  if  JsonObj has  address             Checking address Key Present or not     String get address   JsonObj  getString  address       Present Key   else         Do Your Staff

[java] How to check if a json key exists?

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