Achilles is an open source advanced object mapper for Apache Cassandra. Its feature include

Advanced bean mapping (compound primary key, composite partition key, timeUUID, counter, static column …)
Pluggable codec system to define your own types
Life cycle interceptors to define custom behavior before INSERT/UPDATE/DELETE/SELECT operations
Fluent options system to parameter runtime statements (consistency level, retry policy, …)
Powerful and type-safe DSL to create your own queries
Display of DML scripts & DDL statements
Wrapper to deploy an embedded Cassandra server easily
Tight integration with JUnit for productive TDD programming
Support for Bean Validation (JSR-303)
Support for Lightweight Transaction with dedicated listener interface
Support for Materialized View
Support for typed-safe Function calls
Support for the new JSON API
Support for multi-project compilation unit
Support for native index, SASI and DSE Search
Flexible naming strategy & insert strategy
Runtime Schema Name Provider for multi-tenant environments
Full compatibility with Java 8 CompletableFuture

Hector - Java client for Apache Cassandra