Troubleshooting

Loading too many objects / StackOverflowError

If you get an java.lang.StackOverflowError and the Stacktrace contains lines like these:

at org.zoodb.internal.DataDeSerializer.postProcessCollections(DataDeSerializer.java:334)

and these

at YOUR_CLASS_HERE.hashCode(YOUR_CLASS_HERE.java:129)
at java.util.HashMap.hash(HashMap.java:366)

then ZooDB is recursively loading too many objects into the client. Objects are loaded because the objects contain a HashMap (or similar) or other objects. Whenever an object is loaded into memory, 'empty' objects are used fill any HashMaps it has. However, filling such a HashMap involves calling hashCode() on the empty objects, which in turn causes them to become non-empty (materialised in memory). If these objects also contains HashMaps, then we or loading objects in that HashMap as well.

Solution: Avoid using HashMap (use IdenityHashMap instead), or avoid implementing hashCode(), or use something like this if possible:

@Override
public int hashCode() {
	return super.hashCode();
}