Java: Using Gson in an Applet causes SecurityException

Question

I'm trying to use Google Gson in my Java Applet, but when I do I get

Exception in thread "Thread-19" java.security.AccessControlException: access denied (java.lang.reflect.ReflectPermission suppressAccessChecks) at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323) at java.security.AccessController.checkPermission(AccessController.java:546) at java.lang.SecurityManager.checkPermission(SecurityManager.java:532) at java.lang.reflect.AccessibleObject.setAccessible(AccessibleObject.java:74) at com.google.gson.MappedObjectConstructor.getNoArgsConstructor(MappedObjectConstructor.java:85) at com.google.gson.MappedObjectConstructor.constructWithNoArgConstructor(MappedObjectConstructor.java:62) at com.google.gson.MappedObjectConstructor.construct(MappedObjectConstructor.java:53) at com.google.gson.JsonObjectDeserializationVisitor.constructTarget(JsonObjectDeserializationVisitor.java:40) at com.google.gson.JsonDeserializationVisitor.getTarget(JsonDeserializationVisitor.java:56) at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:109) at com.google.gson.JsonDeserializationContextDefault.fromJsonObject(JsonDeserializationContextDefault.java:73) at com.google.gson.JsonDeserializationContextDefault.deserialize(JsonDeserializationContextDefault.java:51) at com.google.gson.Gson.fromJson(Gson.java:495) at com.google.gson.Gson.fromJson(Gson.java:444) at com.google.gson.Gson.fromJson(Gson.java:396) at com.google.gson.Gson.fromJson(Gson.java:372) at org.jblux.client.network.GsonParser$1.run(GsonParser.java:32) at java.security.AccessController.doPrivileged(Native Method) at org.jblux.client.network.GsonParser.parseJson(GsonParser.java:36) at org.jblux.client.network.PlayerDataFactory.getDataFromBase64(PlayerDataFactory.java:36) at org.jblux.client.states.MainMenuState.update(MainMenuState.java:155) at java.util.Observable.notifyObservers(Observable.java:142) at org.jblux.client.network.ResponseWaiter.responseReceived(ResponseWaiter.java:33) at org.jblux.client.network.ServerListener.notify_observers(ServerCommunicator.java:236) at org.jblux.client.network.ServerListener.doCommand(ServerCommunicator.java:252) at org.jblux.client.network.ServerListener.run(ServerCommunicator.java:218)

There were two other related questions I found here.
GSON on Google App Engine throws a Security Exception
Reflection Permission problems when using the GSON library in a applet

But neither of them had an answer for me. One just said to not use Gson.
Is there any way to grant Reflection permission to my applet?

Update: I'm in the process of switching my application to use JNLP file and Java Web Start because I haven't been able to figure out how to make the Applet work. I'll leave this question open in case anybody figures it out, but using a JNLP may be the only option if you don't want to give up Gson.

Answer 1

I solved this problem using a custom deserializer.

I had a class with two members, a timestamp and a list of doubles. This is the code that worked for me.

GsonBuilder gsonBuilder = new GsonBuilder();
    gsonBuilder.registerTypeAdapter(TimestampedValueList.class, new JsonDeserializer<TimestampedValueList>() {
        @Override
        public TimestampedValueList deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
            long timestampMs = json.getAsJsonObject().get("timestampMs").getAsLong();
            double[] valueList = context.deserialize(json.getAsJsonObject().get("valueList"), double[].class);
            return new TimestampedValueList(timestampMs, valueList);
        }
    });
gson = gsonBuilder.create();

Hope this can help anyone!