Question

I want to parse a JSON object using GSON. Everything seems to work fine but when I’m trying to parse a more “complexed” object I’m getting a deserialization error. The object I’m trying to parse contains some primitives, a stack and a vector collection.

Is it possible that the stack\vector causing this problem? can I somehow over come this?

The Error:

Exception in thread "AWT-EventQueue-0" com.google.gson.JsonParseException: The JsonDeserializer com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter@4e76fba0 failed to deserialize json object [{"name_":"Human","points_":1,"alive_":true,"id_":0,"cssStyleClass":"pressed_p1"},{"name_":"Human","points_":0,"alive_":true,"id_":1,"cssStyleClass":"pressed_p2"}] given the type java.util.Vector<entities.Player>
    at com.google.gson.JsonDeserializerExceptionWrapper.deserialize(JsonDeserializerExceptionWrapper.java:64)
    at com.google.gson.JsonDeserializationVisitor.invokeCustomDeserializer(JsonDeserializationVisitor.java:92)
    at com.google.gson.JsonObjectDeserializationVisitor.visitFieldUsingCustomHandler(JsonObjectDeserializationVisitor.java:117)
    at com.google.gson.ReflectingFieldNavigator.visitFieldsReflectively(ReflectingFieldNavigator.java:63)
    at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:120)
    at com.google.gson.JsonDeserializationContextDefault.fromJsonObject(JsonDeserializationContextDefault.java:76)
    at com.google.gson.JsonDeserializationContextDefault.deserialize(JsonDeserializationContextDefault.java:54)

Request Code

Gson json = new Gson();
Multiplayer result = json.fromJson(answer.toString(), Multiplayer.class);

Code On Servlet

Gson gson = new Gson();
Multiplayer game = (Multiplayer)getServletContext().getAttribute("OnlineGame");
String responseStr = gson.toJson(game);

response.setContentType("application/json;charset=UTF-8");
out.write(responseStr);

String from toString()

{serializeNulls:false,serializers:{mapForTypeHierarchy:{Map:MapTypeAdapter,Collection:com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter@596e1fb1,InetAddress:com.google.gson.DefaultTypeAdapters$DefaultInetAddressAdapter@4ce2cb55,Enum:EnumTypeAdapter},map:{Integer:IntegerTypeAdapter,URI:UriTypeAdapter,UUID:UuidTypeAdapter,BigInteger:BigIntegerTypeAdapter,URL:UrlTypeAdapter,Short:ShortTypeAdapter,Time:com.google.gson.DefaultTypeAdapters$DefaultTimeTypeAdapter@16bdb503,byte:ByteTypeAdapter,short:ShortTypeAdapter,Number:NumberTypeAdapter,double:com.google.gson.DefaultTypeAdapters$DoubleSerializer@b6e39f,GregorianCalendar:GregorianCalendarTypeAdapter,Calendar:GregorianCalendarTypeAdapter,Byte:ByteTypeAdapter,StringBuilder:StringBuilderTypeAdapter,Float:com.google.gson.DefaultTypeAdapters$FloatSerializer@6719dc16,Locale:LocaleTypeAdapter,StringBuffer:StringBufferTypeAdapter,Date:DefaultDateTypeAdapter(SimpleDateFormat),Character:CharacterTypeAdapter,float:com.google.gson.DefaultTypeAdapters$FloatSerializer@6719dc16,BigDecimal:BigDecimalTypeAdapter,Boolean:BooleanTypeAdapter,boolean:BooleanTypeAdapter,String:StringTypeAdapter,Timestamp:DefaultDateTypeAdapter(SimpleDateFormat),int:IntegerTypeAdapter,long:LongSerializer,Date:com.google.gson.DefaultTypeAdapters$DefaultJavaSqlDateTypeAdapter@52c05d3b,char:CharacterTypeAdapter,Double:com.google.gson.DefaultTypeAdapters$DoubleSerializer@b6e39f,Long:LongSerializer},deserializers:{mapForTypeHierarchy:{Map:MapTypeAdapter,Collection:com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter@596e1fb1,InetAddress:com.google.gson.DefaultTypeAdapters$DefaultInetAddressAdapter@4ce2cb55,Enum:EnumTypeAdapter},map:{Integer:IntegerTypeAdapter,URI:UriTypeAdapter,UUID:UuidTypeAdapter,BigInteger:BigIntegerTypeAdapter,URL:UrlTypeAdapter,Short:ShortTypeAdapter,byte:ByteTypeAdapter,Time:com.google.gson.DefaultTypeAdapters$DefaultTimeTypeAdapter@16bdb503,short:ShortTypeAdapter,Number:NumberTypeAdapter,double:DoubleDeserializer,Byte:ByteTypeAdapter,Calendar:GregorianCalendarTypeAdapter,GregorianCalendar:GregorianCalendarTypeAdapter,StringBuilder:StringBuilderTypeAdapter,Float:FloatDeserializer,Locale:LocaleTypeAdapter,StringBuffer:StringBufferTypeAdapter,Date:DefaultDateTypeAdapter(SimpleDateFormat),Character:CharacterTypeAdapter,float:FloatDeserializer,BigDecimal:BigDecimalTypeAdapter,Boolean:BooleanTypeAdapter,boolean:BooleanTypeAdapter,String:StringTypeAdapter,Timestamp:com.google.gson.DefaultTypeAdapters$DefaultTimestampDeserializer@5328f6ee,int:IntegerTypeAdapter,long:LongDeserializer,Date:com.google.gson.DefaultTypeAdapters$DefaultJavaSqlDateTypeAdapter@52c05d3b,char:CharacterTypeAdapter,Double:DoubleDeserializer,Long:LongDeserializer},instanceCreators:{mapForTypeHierarchy:{SortedSet:DefaultConstructorCreator,Set:DefaultConstructorCreator,Queue:DefaultConstructorCreator,Collection:DefaultConstructorCreator,Map:DefaultConstructorCreator},map:{}}

Answer 1

I recommend you to use an array Player[] instead of the generic collection Vector<Player>. It’s not easy to use Java generics for serializing and deserializing. If you use an array instead, you will have no problem with it.

But it had been easier to answer if you show your code for Multiplayer and Player.