Expected BEGIN OBJECT but was STRING at line 1 column 1

Question

I have this method   public static Object parseStringToObject String json        String Object   json      Gson gson   new Gson        Object objects   gson fromJson object  Object class       parseConfigFromObjectToString object       return objects      And I want to parse a JSON with   public static void addObject String IP  Object addObject        try           String json   sendPostRequest  http       IP     3000 config add Object   ConfigJSONParser parseConfigFromObjectToString addObject            addObject   ConfigJSONParser parseStringToObject json         catch  Exception ex            ex printStackTrace              But I get an error message      com google gson JsonSyntaxException  java lang IllegalStateException    Expected BEGIN OBJECT but was STRING at line 1 column 1

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In my case  my custom http-client didn t support the gzip encoding  I was sending the  quot Accept-Encoding  gzip quot  header  and so the response was sent back as a gzip string and couldn t be decoded  The solution was to not send that header

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Make sure you have DESERIALIZED objects like DATE DATETIME etc  If you are directly sending JSON without deserializing it then it can cause this problem

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Don t use jsonObject toString on a JSON object

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Don t forget to convert your object into Json first using Gson      val fromUserJson   Gson   toJson notificationRequest fromUser    Then you can easily convert it back into an object using this awesome library        val fromUser   Gson   fromJson fromUserJson  User  class java

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if your json format and variables are okay then check your database queries   even if data is saved  in db correctly the actual problem might be in there   recheck your queries and try again   Hope it helps

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In my situation  I have a  model   consist of several String parameters  with the exception of one  it is byte array byte    Some code snippet   String response   args 0  toString    Gson gson   new Gson    BaseModel responseModel   gson fromJson response  BaseModel class     The last line above is when the  java lang IllegalStateException  Expected BEGIN OBJECT but was STRING at line 1 column   is triggered  Searching through the SO  I realised I need to have some form of Adapter to convert my BaseModel to and fro a JsonObject  Having mixed of String and byte   in a model does complicate thing  Apparently  Gson don t really like the situation   I end up making an Adapter to ensure byte   is converted to Base64 format  Here is my Adapter class   public class ByteArrayToBase64Adapter implements JsonSerializer lt byte   gt   JsonDeserializer lt byte   gt          Override     public byte   deserialize JsonElement json  Type typeOfT  JsonDeserializationContext context  throws JsonParseException           return Base64 decode json getAsString    Base64 NO WRAP               Override     public JsonElement serialize byte   src  Type typeOfSrc  JsonSerializationContext context            return new JsonPrimitive Base64 encodeToString src  Base64 NO WRAP              To convert JSONObject to model  I used the following   Gson customGson   new GsonBuilder   registerTypeHierarchyAdapter byte   class  new ByteArrayToBase64Adapter    create    BaseModel responseModel   customGson fromJson response  BaseModel class     Similarly  to convert the model to JSONObject  I used the following   Gson customGson   new GsonBuilder   registerTypeHierarchyAdapter byte   class  new ByteArrayToBase64Adapter    create    String responseJSon   customGson toJson response     What the code is doing is basically to push the intended class object  in this case  byte   class  through the Adapter whenever it is encountered during the convertion to fro JSONObject

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I had a case where I read from a handwritten json file  The json is perfect  However  this error occurred  So I write from a java object to json file  then read from that json file  things are fine  I could not see any difference between the handwritten json and the one from java object  Tried beyondCompare it sees no difference  I finally noticed the two file sizes are slightly different  and I used winHex tool and detected extra stuff  So the solution for my situation is  make copy of the good json file  paste content into it and use

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Invalid JSON from the server should always be an expected use case  A million things can go wrong during transmission  Gson is a bit tricky  because its error output will give you one problem  and the actual exception you catch will be of a different type   With all that in mind  the proper fix on the client side is  try     gson fromJSON ad  Ad class             catch  IllegalStateException   JsonSyntaxException exception              If you want to know why the JSON you received from the server is wrong  you can look inside your catch block at the exception  But even if it is your problem  it s not the client s responsibility to fix JSON it is receiving from the internet   Either way  it is the client s responsibility to decide what to do when it gets bad JSON  Two possibilities are rejecting the JSON and doing nothing  and trying again   If you are going to try again  I highly recommend setting a flag inside the try   catch block and then responding to that flag outside the try   catch block  Nested try   catch is likely how Gson got us into this mess with our stack trace and exceptions not matching up   In other words  even though I ll admit it doesn t look very elegant  I would recommend  boolean failed   false   try     gson fromJSON ad  Ad class             catch  IllegalStateException   JsonSyntaxException exception      failed   true             if  failed

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I have come to share an solution  The error happened to me after forcing the notbook to hang up  possible solution clean preject

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Maybe your JSON Object is right but the response that you received is not your valid data Just like when you connect the invalid WiFi you may received a strange response  lt  html gt       lt   html gt  that GSON can not parse   you may need to do some try  catch   for this strange response to avoid crash

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In Retrofit2  When you want to send your parameters in raw you must use Scalars   first add this in your gradle       compile  com squareup retrofit2 retrofit 2 3 0      compile  com squareup retrofit2 converter-gson 2 3 0      compile  com squareup retrofit2 converter-scalars 2 3 0       public interface ApiInterface        String URL BASE    http   10 157 102 22 rest          Headers  Content-Type  application json        POST  login       Call lt User gt  getUser  Body String body        my SampleActivity       public class SampleActivity extends AppCompatActivity implements Callback lt User gt          Override     protected void onCreate  Nullable Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity sample            Retrofit retrofit   new Retrofit Builder                    baseUrl ApiInterface URL BASE                   addConverterFactory ScalarsConverterFactory create                     addConverterFactory GsonConverterFactory create                     build             ApiInterface apiInterface   retrofit create ApiInterface class                prepare call in Retrofit 2 0         try               JSONObject paramObject   new JSONObject                paramObject put  email    sample gmail com                paramObject put  pass    4384984938943                 Call lt User gt  userCall   apiInterface getUser paramObject toString                 userCall enqueue this             catch  JSONException e                e printStackTrace                           Override     public void onResponse Call lt User gt  call  Response lt User gt  response                Override     public void onFailure Call lt User gt  call  Throwable t              Reference   How to POST raw whole JSON in the body of a Retrofit request

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Even without seeing your JSON string you can tell from the error message that it is not the correct structure to be parsed into an instance of your class   Gson is expecting your JSON string to begin with an object opening brace  e g        But the string you have passed to it starts with an open quotes

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I had a similar problem recently and found an interesting solution  Basically I needed to deserialize following nested JSON String into my POJO   quot    quot restaurant  quot     quot id  quot    quot abc-012  quot    quot name  quot    quot good restaurant  quot    quot foodType  quot    quot American  quot    quot phoneNumber  quot    quot 123-456-7890  quot    quot currency  quot    quot USD  quot    quot website  quot    quot website com  quot    quot location  quot     quot address  quot     quot street  quot    quot  Good Street  quot    quot city  quot    quot Good City  quot    quot state  quot    quot CA  quot    quot country  quot    quot USA  quot    quot postalCode  quot    quot 12345  quot     quot coordinates  quot     quot latitude  quot    quot 00 7904692  quot    quot longitude  quot    quot -000 4047208  quot      quot restaurantUser  quot     quot firstName  quot    quot test  quot    quot lastName  quot    quot test  quot    quot email  quot    quot test test com  quot    quot title  quot    quot server  quot    quot phone  quot    quot 0000000000  quot     quot   I ended up using regex to remove the open quotes from beginning and the end of JSON and then used apache commons unescapeJava   method  to unescape it  Basically passed the unclean JSON into following method to get back a cleansed one  private String removeQuotesAndUnescape String uncleanJson        String noQuotes   uncleanJson replaceAll  quot    quot    quot   quot    quot  quot         return StringEscapeUtils unescapeJava noQuotes      then used Google GSON to parse it into my own Object  MyObject myObject   new Gson   fromJson this removeQuotesAndUnescape uncleanJson

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In my case  I am Returning JSON Object as        data      message   Attendance Saved   Successfully        status   success     Resolved by changing it as        data      message   Attendance Saved   Successfully        status   success     Here data is a sub JsonObject and it should starts from   not

[java] "Expected BEGIN_OBJECT but was STRING at line 1 column 1"

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