How to store complex objects into hadoop Hbase?
HBase only deals with byte arrays, so you can serialize your object in any way you see fit.
The standard Hadoop way of serializing objects is to implement the org.apache.hadoop.io.Writable interface. Then you can serialize your object into a byte array using org.apache.hadoop.io.WritableUtils.toByteArray(Writable ... writable).
Also, there are other serialization frameworks that people in the Hadoop community use, like Avro, Protocol Buffers, and Thrift. All have their specific use cases, so do your research. If you're doing something simple, implementing Hadoop's Writable should be good enough.