ConcurrentModificationException in Flexjson

Question

I'm sometimes getting this error when serialising an object

flexjson.JSONException: Error trying to deepSerialize
        at flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:61)
        at flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
        at flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:49)
        at flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
        at flexjson.JSONContext.transform(JSONContext.java:73)
        at flexjson.JSONSerializer.serialize(JSONSerializer.java:377)
        at flexjson.JSONSerializer.deepSerialize(JSONSerializer.java:301

...
Caused by: java.util.ConcurrentModificationException
        at java.base/java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1042)
        at java.base/java.util.ArrayList$Itr.next(ArrayList.java:996)
        at flexjson.JSONContext.matches(JSONContext.java:434)

With this String sessionJson = serializer.exclude("*.class").deepSerialize(response);

Can anyone tell me what ConcurrentModificationException is all about?

Answer 1

Possible that same instance of JSONSerializer is shared between two threads and along with serialize, there are other calls/invocations. Check the calls to includes/excludes, use, transforms etc., which should be before the first thread invokes serialize.

Other option is to use CopyOnWriteArrayList , such as :

serializer = new flexjson.JSONSerializer();
List pathExpressions = (List)BeanUtil.getDeclaredProperty(serializer, "pathExpressions");
pathExpressions = new CopyOnWriteArrayList(pathExpressions);
BeanUtil.setDeclaredProperty(serializer, "pathExpressions", pathExpressions);