How to make a list thread-safe for serialization?

Question

I am using a ThreadSafeList and I am getting great mileage out of it for streaming data from a process to a webserver and then streaming the data back out as it comes in to a client. In memory I am saving the data in the JVM with Spring Caching (ehcache under the hood) and all is well. The trouble started when I started hitting my heap limits and Spring Caching started serializing my ThreadSafeList to disk while I am using it, causing ConcurrentModificationExceptions. Can I overwrite the private writeObject and readObject methods for the Serialization interface to solve the problem? I am unsure of how to do this or if I should abandon my ThreadSafeList.

Back when I started this program I was using a BlockingDeque, but it wasn't sufficient because as I put and take on the structure I couldn't remember the data for caching... I can't use a ConcurrentMap because I need ordering in my list... should I go for ConcurrentNavigableMap? I feel like rolling my own with a ThreadSafeList and custom private serialization functions might be a waste?

Java Code Geeks ThreadSafeList

Spring caching does not such thing if that can help you track down where the problem is coming from. — Stephane Nicoll, Mar 26 '15 at 08:16

score 1 · Accepted Answer · answered Apr 02 '15 at 00:28

Collections.synchronizedList() will make any List thread-safe and supports serialization (if the underlying list is Serializable). Remember to synchronize on the list if you need to iterate over it.

e.g.

@Cacheable
public List<String> getData(String clientName) {
    List<String> data = Collections.synchronizedList(new ArrayList<String>());
    // load data for the client from external process and add it to the list...
    return data;
}

How to make a list thread-safe for serialization?

1 Answers1