[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-772) null in maps are handled inconsistently

[ http://opensource.atlassian.com/projects/hibernate/browse/HHH-772?page=co... ] Ferenc Gratzer commented on HHH-772: ------------------------------------ I want to share how this old and insane hibernate issue could be circumvented fairly easy. Let's take the next example: public class Owner { private Map<KeyClass, ValueClass> mapping = new HashMap<KeyClass, ValueClass>(); public ValueClass getMappingValue(KeyClass keyClass) { return mapping.get(keyClass); } public void addMapping(KeyClass keyClass, ValueClass valueClass) { mapping.put(keyClass, valueClass); } } This wouldn't work if the value of the map is null. owner.addMapping(keyClass, null) 1) Add a new dummy boolean column to the mapping table: ALTER TABLE MAPPING_TABLE ADD DUMMY SMALLINT DEFAULT 0 NOT NULL; 2) Add a <composite-element> as the value of the map: <map name="mapping" cascade="all" fetch="select" lazy="true" mutable="true" inverse="false" table="MAPPING_TABLE"> <cache usage="read-write" /> <key column="OWNER_ID" not-null="true" /> <map-key-many-to-many class="KeyClass" column="KEY_ID" /> <!-- This composite element is only created as Hibernate doesn't allow null as map value, see HHH-772 --> <composite-element class="MapValueClass"> <many-to-one name="mapValue" column="VALUE_ID" class="ValueClass" /> <property name="dummy" column="DUMMY" not-null="true" type="boolean" /> </composite-element> </map> 3) Create a MapValueClass class: public class MapValueClass { private ValueClass valueClass; @SuppressWarnings("unused") private boolean dummy; @SuppressWarnings("unused") private MapValueClass() { // Hibernate } public MapValueClass(ValueClass valueClass) { this.valueClass = valueClass; } public ValueClass getValueClass() { return valueClass; } } 4) Change the mapping configuration in Owner class: class Owner { Map<KeyClass, MapValueClass> mapping = new HashMap<KeyClass, MapValueClass>(); public ValueClass getMappingValue(KeyClass keyClass) { return mapping.get(keyClass).getValueClass(); } public void addMapping(KeyClass keyClass, ValueClass valueClass) { mapping.put(keyClass, new MapValueClass(valueClass)); } } Now the owner.addMapping(keyObject, null) works fine. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://opensource.atlassian.com/projects/hibernate/secure/Administrators.... - For more information on JIRA, see: http://www.atlassian.com/software/jira