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 deni

Answer 1

Further to @Chrizzz, I'm doing two way command object exchange between a Java web server and an unsigned applet. As such I am using both Gson toJson() and fromJson() within my applet code.

I've found that both deserialization and serialization in an unsigned applet throw security exceptions and that implementing custom serializers and deserializers can work-around those problems.

The biggest pain is not being able emulate the applet environment (SecurityManager) for Unit testing. It seems that there are no frameworks available to do this: see e.g. How to unit test Java code that is expected to run within an applet Security Manager

Answer 2

I have found the answer here.

System.setSecurityManager(null);

Adding to static main helped me. Of course, all-permissions in jnlp and so on must be.

Answer 3

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!