@Override
  public boolean equals(Object o) {
    if (this == o) return true;
    
    if (o == null || getClass() != o.getClass()) return false;

    HostConfigMappingEntityPK that = (HostConfigMappingEntityPK) o;

    if (clusterId != null ? !clusterId.equals(that.clusterId) : that.clusterId != null) return false;
    if (hostId != null ? !hostId.equals(that.hostId) : that.hostId != null) return false;
    if (type != null ? !type.equals(that.type) : that.type != null) return false;
    if (createTimestamp != null ? !createTimestamp.equals (that.createTimestamp) : that.createTimestamp != null) return false;

    return true;
  }
PK class for host config mappings.
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/HostConfigMappingEntityPK.java