[Bug] MessageEvent doesn`t support plain string in payload. (Probable fix provided)

[bivashy]

I'm executing this request (replace with URI from your logs): https://lp.vk.com/wh*******

with parameters (replace with params from your logs): wait=25&act=a_check&key=***&ts=19695

and I'm receiving (replace with response from your logs):

{"ts":"19696","updates":[{"group_id":203083412,"type":"message_event","event_id":"ae8e0ea6cca21fb263f871ca5aded4c59d91dc51","v":"5.131","object":{"user_id":205639000,"peer_id":205639000,"event_id":"15a1124fb169","payload":"\/принять Username","conversation_message_id":5187}}]}

Here is the code example (replace with your code example):

public class VkBotTest extends LongPollBot {
    private static final String GROUP_TOKEN = "TOKEN_HERE";

    public static void main(String[] args) throws VkApiException {
        new VkBotTest().startPolling();
    }

    @Override
    public void onMessageEvent(MessageEvent messageEvent) {
        System.out.println(messageEvent.getEventId());
        System.out.println(messageEvent.getConversationMessageId());
        System.out.println(messageEvent.getPayload());
    }

    @Override
    public String getAccessToken() {
        return GROUP_TOKEN;
    }
}
}

Stacktrace:

Exception in thread "main" com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Expected value at line 1 column 1 path $
	at com.google.gson.Gson.fromJson(Gson.java:902)
	at com.google.gson.Gson.fromJson(Gson.java:852)
	at com.google.gson.Gson.fromJson(Gson.java:801)
	at com.google.gson.Gson.fromJson(Gson.java:773)
	at api.longpoll.bots.adapters.deserializers.PayloadDeserializer.deserialize(PayloadDeserializer.java:23)
	at api.longpoll.bots.adapters.deserializers.PayloadDeserializer.deserialize(PayloadDeserializer.java:14)
	at com.google.gson.internal.bind.TreeTypeAdapter.read(TreeTypeAdapter.java:69)
	at com.google.gson.TypeAdapter$1.read(TypeAdapter.java:199)
	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:129)
	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:220)
	at com.google.gson.Gson.fromJson(Gson.java:887)
	at com.google.gson.Gson.fromJson(Gson.java:952)
	at com.google.gson.internal.bind.TreeTypeAdapter$GsonContextImpl.deserialize(TreeTypeAdapter.java:162)
	at api.longpoll.bots.adapters.deserializers.UpdateDeserializer.deserialize(UpdateDeserializer.java:66)
	at api.longpoll.bots.adapters.deserializers.UpdateDeserializer.deserialize(UpdateDeserializer.java:47)
	at com.google.gson.internal.bind.TreeTypeAdapter.read(TreeTypeAdapter.java:69)
	at com.google.gson.TypeAdapter$1.read(TypeAdapter.java:199)
	at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:41)
	at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82)
	at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)
	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:129)
	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:220)
	at com.google.gson.Gson.fromJson(Gson.java:887)
	at com.google.gson.Gson.fromJson(Gson.java:852)
	at com.google.gson.Gson.fromJson(Gson.java:801)
	at com.google.gson.Gson.fromJson(Gson.java:773)
	at api.longpoll.bots.methods.impl.VkMethod.execute(VkMethod.java:130)
	at api.longpoll.bots.LongPollBot.startPolling(LongPollBot.java:73)
	at com.ubivashka.java.test.VkBotTest.main(VkBotTest.java:14)
Caused by: com.google.gson.stream.MalformedJsonException: Expected value at line 1 column 1 path $
	at com.google.gson.stream.JsonReader.syntaxError(JsonReader.java:1559)
	at com.google.gson.stream.JsonReader.doPeek(JsonReader.java:590)
	at com.google.gson.stream.JsonReader.peek(JsonReader.java:425)
	at com.google.gson.Gson.fromJson(Gson.java:883)
	... 28 more

I'm using java-vk-bots-longpoll-api version (replace with version you are using): 4.1.0

Could you please help me to understand what is wrong here?

My thoughts: This is issue with payload. I am sending its as an string. But api.longpoll.bots.adapters.deserializers.PayloadDeserializer tries to parse it as json. Yes, i can fix this issue with just changing payload. But i hope you`ll fix that

I think fixed version would be:

public class PayloadDeserializer implements JsonDeserializer<JsonElement> {
    /**
     * {@link Gson} object.
     */
    private static final Gson GSON = new Gson();

    @Override
    public JsonElement deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext context) throws JsonParseException {
        return jsonElement;
    }
}

Because GSON.fromJson(jsonElement.getAsString(), JsonElement.class) cannot process simple strings.

Good luck! And have a good day!