HBase1.2官方文档——ApacheHBaseCoprocessors

public class SumEndPoint extends SumService implements Coprocessor, CoprocessorService {

    private RegionCoprocessorEnvironment env;

    @Override
    public Service getService() {
        return this;
    }

    @Override
    public void start(CoprocessorEnvironment env) throws IOException {
        if (env instanceof RegionCoprocessorEnvironment) {
            this.env = (RegionCoprocessorEnvironment)env;
        } else {
            throw new CoprocessorException("Must be loaded on a table region!");
        }
    }

    @Override
    public void stop(CoprocessorEnvironment env) throws IOException {
        // do mothing
    }

    @Override
    public void getSum(RpcController controller, SumRequest request, RpcCallback done) {
        Scan scan = new Scan();
        scan.addFamily(Bytes.toBytes(request.getFamily()));
        scan.addColumn(Bytes.toBytes(request.getFamily()), Bytes.toBytes(request.getColumn()));
        SumResponse response = null;
        InternalScanner scanner = null;
        try {
            scanner = env.getRegion().getScanner(scan);
            List results = new ArrayList();
            boolean hasMore = false;
                        long sum = 0L;
                do {
                        hasMore = scanner.next(results);
                        for (Cell cell : results) {
                            sum = sum + Bytes.toLong(CellUtil.cloneValue(cell));
                     }
                        results.clear();
                } while (hasMore);

                response = SumResponse.newBuilder().setSum(sum).build();

        } catch (IOException ioe) {
            ResponseConverter.setControllerException(controller, ioe);
        } finally {
            if (scanner != null) {
                try {
                    scanner.close();
                } catch (IOException ignored) {}
            }
        }
        done.run(response);
    }
}
Configuration conf = HBaseConfiguration.create();
// Use below code for HBase version 1.x.x or above.
Connection cOnnection= ConnectionFactory.createConnection(conf);
TableName tableName = TableName.valueOf("users");
Table table = connection.getTable(tableName);

//Use below code HBase version 0.98.xx or below.
//HConnection cOnnection= HConnectionManager.createConnection(conf);
//HTableInterface table = connection.getTable("users");

final SumRequest request = SumRequest.newBuilder().setFamily("salaryDet").setColumn("gross")
                            .build();
try {
Map<byte[], Long> results = table.CoprocessorService (SumService.class, null, null,
new Batch.Call() {
    @Override
        public Long call(SumService aggregate) throws IOException {
BlockingRpcCallback rpcCallback = new BlockingRpcCallback();
            aggregate.getSum(null, request, rpcCallback);
            SumResponse response = rpcCallback.get();
            return response.hasSum() ? response.getSum() : 0L;
        }
    });
    for (Long sum : results.values()) {
        System.out.println("Sum = " + sum);
    }
} catch (ServiceException e) {
e.printStackTrace();
} catch (Throwable e) {
    e.printStackTrace();
}