Recursive asynchronous HBase scanning

ScannerTest.java

package me.alexyang.scanner;

import java.nio.charset.Charset;
import java.util.ArrayList;

import org.jboss.netty.util.CharsetUtil;

import com.stumbleupon.async.Callback;
import com.stumbleupon.async.Deferred;
import org.hbase.async.HBaseClient;
import org.hbase.async.KeyValue;
import org.hbase.async.Scanner;

/**
 * @author Alex Yang <alex890714@gmail.com>
 */
public class ScannerTest {

  public static void main(String[] args) throws Exception {
    final HBaseClient hbase = new HBaseClient("centos-pd.alexyang.me");
    try {
      hbase.ensureTableExists("query").joinUninterruptibly();

      final Scanner scanner = hbase.newScanner("query");
      try {
        scanner.setFamily("dims");
        scanner.setQualifier("val");

        final ArrayList<String> results = new ArrayList<String>();

        class ResultHandler implements Callback<Object, ArrayList<ArrayList<KeyValue>>> {

          public Object call(ArrayList<ArrayList<KeyValue>> t) throws Exception {
            if (t == null) {
              return null;
            }
            for (ArrayList<KeyValue> arr : t) {
              for (KeyValue kv : arr) {
                results.add(new String(kv.value(), CharsetUtil.ISO_8859_1));
              }
            }
            return scanner.nextRows().addCallback(ResultHandler.this);
          }
        }

        scanner.nextRows().addCallback(new ResultHandler()).join();

        for (String str : results) {
          System.out.println(str);
        }
      } finally {
        scanner.close().joinUninterruptibly();
      }
    } finally {
      hbase.shutdown().joinUninterruptibly();
    }
  }
}