Hibernate does not properly deal with empty strings in maps on Oracle --------------------------------------------------------------------- Key: HHH-1173 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1173 Project: Hibernate Core Issue Type: Bug Components: core Affects Versions: 3.1 rc2 Reporter: Keith D Gregory Attachments: null-value-bug.tar.gz This is really a duplicate of HHH-772, but has an actual use case, rather than an abstract "maps should contain nulls" 1) Define an object that contains a map property 2) Create an instance of that object, insert a map entry that contains an empty string as its value, persist 3) Retrieve the object - note that the map now contains the mapping key -> null 4) Use putAll() to copy the map entries from the first object to a new object, persist the new object 5) Retrieve both, note that the second map does not contain the same entries as the first Incidentally, the java.util.Map API has the following to say about null values: "Some map implementations have restrictions on the keys and values they may contain. For example, some implementations prohibit null keys and values, and some have restrictions on the types of their keys. Attempting to insert an ineligible key or value throws an unchecked exception, typically NullPointerException or ClassCastException."