Hazelcast's distributed map implementation (IMap) has capability of indexing attributes of entry values. These indexes can be created using IMap API. But this usage has a limitation; all indexes must be created before any value is put into map. Sometimes by design adding an index to map may be impossible before any value is added. For example if a map has MapLoader that loads entries during map creation, then adding indexes to map becomes meaningless. To solve this problem, Hazelcast introduces defining IMap indexes in configuration.
Hazelcast XML configuration
<map name="default">
...
<indexes>
<index ordered="false">name</index>
<index ordered="true">age</index>
</indexes>
</map>
Config API
mapConfig.addMapIndexConfig(new MapIndexConfig("name", false));
mapConfig.addMapIndexConfig(new MapIndexConfig("age", true));
Spring XML configuration
<hz:map name="default">
<hz:indexes>
<hz:index attribute="name"/>
<hz:index attribute="age" ordered="true"/>
</hz:indexes>
</hz:map>