Use asynchbase to get or create an id for key.

gistfile1.txt

package me.alexyang.deferred;

import com.stumbleupon.async.Callback;
import com.stumbleupon.async.Deferred;
import java.util.ArrayList;
import org.hbase.async.Bytes;
import org.hbase.async.GetRequest;
import org.hbase.async.HBaseClient;
import org.hbase.async.KeyValue;
import org.hbase.async.PutRequest;

/**
 *
 * @author Alex Yang <[email protected]> 
 */
public class TestDeferred {

    public static void main(String[] args) throws Exception {

        final String table = "test";
        final String rowKey = "key";

        HBaseClient hbase = new HBaseClient("centos-pd.alexyang.me");
        hbase.ensureTableExists("test").joinUninterruptibly();

        GetRequest getRequest = new GetRequest(table, rowKey);
        getRequest.family("id").qualifier("id");

        Deferred<ArrayList<KeyValue>> getIdDeferred;
        getIdDeferred = hbase.get(getRequest);
        Deferred<byte[]> getIdResult = getIdDeferred.
            addCallback(new GetIdResultHandler()).
            addCallbacks(new DoNothingHandler(), new CreateIdHandler(hbase));
        
        System.out.println(Bytes.getInt(getIdResult.joinUninterruptibly()));

        hbase.shutdown().joinUninterruptibly();
    } 

}

class GetIdResultHandler implements Callback<byte[], ArrayList<KeyValue>> {

    public byte[] call(ArrayList<KeyValue> t) throws Exception {

        System.out.println("GetIdResultHandler:call()");

        if (null == t || 0 == t.size()) {
            throw new Exception("No ID.");
        }
        return t.get(0).value();
    }
    
}

class CreateIdHandler implements Callback<byte[], Exception> {

    private final HBaseClient hbase;

    public CreateIdHandler(HBaseClient client) {
        hbase = client;
    }

    public byte[] call(Exception t) throws Exception {

        System.out.println("CreateIdHandler:call()");

        byte[] value = Bytes.fromInt(1);
        PutRequest putRequest = new PutRequest(
            "test".getBytes(), "key".getBytes(), "id".getBytes(),
            "id".getBytes(), value);
        hbase.put(putRequest).joinUninterruptibly();

        GetRequest getRequest = new GetRequest("test", "key");
        getRequest.family("id").qualifier("id");
        
        ArrayList<KeyValue> arrs = hbase.get(getRequest).joinUninterruptibly();
        if (null == arrs || 0 == arrs.size()) {
            return null;
        }
        return arrs.get(0).value();
    }
}

class DoNothingHandler implements Callback<byte[], byte[]> {

    public byte[] call(byte[] t) throws Exception {
        return t;
    }
    
}