001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.coprocessor.example;
019
020import java.io.IOException;
021import java.util.Optional;
022import org.apache.hadoop.hbase.CoprocessorEnvironment;
023import org.apache.hadoop.hbase.client.Scan;
024import org.apache.hadoop.hbase.coprocessor.ObserverContext;
025import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
026import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
027import org.apache.hadoop.hbase.coprocessor.RegionObserver;
028import org.apache.hadoop.hbase.util.Bytes;
029import org.apache.yetus.audience.InterfaceAudience;
030
031/**
032 * A RegionObserver which modifies incoming Scan requests to include additional columns than what
033 * the user actually requested.
034 */
035@InterfaceAudience.Private
036public class ScanModifyingObserver implements RegionCoprocessor, RegionObserver {
037
038  public static final String FAMILY_TO_ADD_KEY = "hbase.examples.coprocessor.scanmodifying.family";
039  public static final String QUALIFIER_TO_ADD_KEY =
040    "hbase.examples.coprocessor.scanmodifying.qualifier";
041
042  private byte[] FAMILY_TO_ADD = null;
043  private byte[] QUALIFIER_TO_ADD = null;
044
045  @Override
046  public void start(@SuppressWarnings("rawtypes") CoprocessorEnvironment env) throws IOException {
047    RegionCoprocessorEnvironment renv = (RegionCoprocessorEnvironment) env;
048    FAMILY_TO_ADD = Bytes.toBytes(renv.getConfiguration().get(FAMILY_TO_ADD_KEY));
049    QUALIFIER_TO_ADD = Bytes.toBytes(renv.getConfiguration().get(QUALIFIER_TO_ADD_KEY));
050  }
051
052  @Override
053  public Optional<RegionObserver> getRegionObserver() {
054    // Extremely important to be sure that the coprocessor is invoked as a RegionObserver
055    return Optional.of(this);
056  }
057
058  @Override
059  public void preScannerOpen(ObserverContext<RegionCoprocessorEnvironment> c, Scan scan)
060    throws IOException {
061    // Add another family:qualifier
062    scan.addColumn(FAMILY_TO_ADD, QUALIFIER_TO_ADD);
063  }
064}