java.io.NotSerializableException: java.util.HashMap$Values

Question

Stacktrace:

org.jboss.remoting.InvocationFailureException: Unable to perform invocation;
nested exception is: java.io.WriteAbortedException: writing aborted;
java.io.NotSerializableException: java.util.HashMap$Values

Sadly, the log doesn't show the line or the class where the serialization problem occurs, but debugging the ESB until the step where problem occurs all the HashMap's that are used have only Serializable objects like String, Long and Date!

Also, the problem occurs when calling a remote method, which is void.

Have you seen something like this before?

score 30 · Accepted Answer · answered Sep 09 '13 at 14:36

Found the problem!

The remote service was trying to throw an Exception encapsulating a Collection of String from HashMap.values():

if (!identifiersMap.isEmpty()) {
    context.setRollbackOnly();

    BusinessException e = new BusinessException();
    e.setValues(identifiersMap.values()); // here is where the problem is
    throw e;
}

HashMap has an inner class named Values (as you can see here), which is an implementation of Collection and is NOT Serializable. So, throwing an exception having the content of HashMap.values(), the remote method will throw a serialization exception instead!

ArrayList, for example, is Serializable and could be used to resolve the issue. Working code:

if (!identifiersMap.isEmpty()) {
    context.setRollbackOnly();

    BusinessException e = new BusinessException();
    e.setValues(new ArrayList(apIdentifiersMap.values())); // problem fixed
    throw e;
}

My case, the remote method was void and it was throwing an Exception, but note:

It will also occur if the remote service return a HashMap$Values instance, for example:

return hashMap.values(); // would also have serialization problems

Once again, the solution would be:

return new ArrayList(hashMap.values()); // problem solved

+1 Since the source is a Map, perhaps you could allow `e.setValues(identifiersMap);` as the Map should be Serializable. — Peter Lawrey, Sep 09 '13 at 14:40
@PeterLawrey Also a great solution, Peter, as always. But I'd rather not change the `setValues` method's signature, since it's being used and handled that way elsewhere. Thank you by the nice contribution. — falsarella, Sep 09 '13 at 14:48
I had the same problem, but with the keySet, thanks for the tip! — Claes Mogren, Mar 06 '14 at 13:56
I had the same problem with GenericJackson2JsonRedisSerializer. When we return a Collection as a result of map.values() method, due to type erasure, there would be issues with deserialization (serialization will happen alright). Solved it by enclosing result in an arraylist. — ahrooran, Sep 01 '23 at 11:30

java.io.NotSerializableException: java.util.HashMap$Values

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