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1   /*
2    * Copyright 2010 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  
21  package org.apache.hadoop.hbase.rest;
22  
23  import java.io.IOException;
24  import java.util.Iterator;
25  
26  import org.apache.commons.logging.Log;
27  import org.apache.commons.logging.LogFactory;
28  import org.apache.hadoop.hbase.HColumnDescriptor;
29  import org.apache.hadoop.hbase.KeyValue;
30  import org.apache.hadoop.hbase.UnknownScannerException;
31  import org.apache.hadoop.hbase.client.HTableInterface;
32  import org.apache.hadoop.hbase.client.HTablePool;
33  import org.apache.hadoop.hbase.client.Result;
34  import org.apache.hadoop.hbase.client.ResultScanner;
35  import org.apache.hadoop.hbase.client.Scan;
36  import org.apache.hadoop.hbase.filter.Filter;
37  import org.apache.hadoop.hbase.rest.model.ScannerModel;
38  import org.apache.hadoop.util.StringUtils;
39  
40  public class ScannerResultGenerator extends ResultGenerator {
41  
42    private static final Log LOG =
43      LogFactory.getLog(ScannerResultGenerator.class);
44  
45    public static Filter buildFilterFromModel(final ScannerModel model) 
46        throws Exception {
47      String filter = model.getFilter();
48      if (filter == null || filter.length() == 0) {
49        return null;
50      }
51      return buildFilter(filter);
52    }
53  
54    private String id;
55    private Iterator<KeyValue> rowI;
56    private KeyValue cache;
57    private ResultScanner scanner;
58    private Result cached;
59  
60    public ScannerResultGenerator(final String tableName, final RowSpec rowspec,
61        final Filter filter) throws IllegalArgumentException, IOException {
62      HTablePool pool = RESTServlet.getInstance().getTablePool(); 
63      HTableInterface table = pool.getTable(tableName);
64      try {
65        Scan scan;
66        if (rowspec.hasEndRow()) {
67          scan = new Scan(rowspec.getStartRow(), rowspec.getEndRow());
68        } else {
69          scan = new Scan(rowspec.getStartRow());
70        }
71        if (rowspec.hasColumns()) {
72          byte[][] columns = rowspec.getColumns();
73          for (byte[] column: columns) {
74            byte[][] split = KeyValue.parseColumn(column);
75            if (split.length > 1 && (split[1] != null && split[1].length != 0)) {
76              scan.addColumn(split[0], split[1]);
77            } else {
78              scan.addFamily(split[0]);
79            }
80          }
81        } else {
82          for (HColumnDescriptor family: 
83              table.getTableDescriptor().getFamilies()) {
84            scan.addFamily(family.getName());
85          }
86        }
87        scan.setTimeRange(rowspec.getStartTime(), rowspec.getEndTime());          
88        scan.setMaxVersions(rowspec.getMaxVersions());
89        if (filter != null) {
90          scan.setFilter(filter);
91        }
92        // always disable block caching on the cluster when scanning
93        scan.setCacheBlocks(false);
94        scanner = table.getScanner(scan);
95        cached = null;
96        id = Long.toString(System.currentTimeMillis()) +
97               Integer.toHexString(scanner.hashCode());
98      } finally {
99        pool.putTable(table);
100     }
101   }
102 
103   public String getID() {
104     return id;
105   }
106 
107   public void close() {
108   }
109 
110   public boolean hasNext() {
111     if (cache != null) {
112       return true;
113     }
114     if (rowI != null && rowI.hasNext()) {
115       return true;
116     }
117     if (cached != null) {
118       return true;
119     }
120     try {
121       Result result = scanner.next();
122       if (result != null && !result.isEmpty()) {
123         cached = result;
124       }
125     } catch (UnknownScannerException e) {
126       throw new IllegalArgumentException(e);
127     } catch (IOException e) {
128       LOG.error(StringUtils.stringifyException(e));
129     }
130     return cached != null;
131   }
132 
133   public KeyValue next() {
134     if (cache != null) {
135       KeyValue kv = cache;
136       cache = null;
137       return kv;
138     }
139     boolean loop;
140     do {
141       loop = false;
142       if (rowI != null) {
143         if (rowI.hasNext()) {
144           return rowI.next();
145         } else {
146           rowI = null;
147         }
148       }
149       if (cached != null) {
150         rowI = cached.list().iterator();
151         loop = true;
152         cached = null;
153       } else {
154         Result result = null;
155         try {
156           result = scanner.next();
157         } catch (UnknownScannerException e) {
158           throw new IllegalArgumentException(e);
159         } catch (IOException e) {
160           LOG.error(StringUtils.stringifyException(e));
161         }
162         if (result != null && !result.isEmpty()) {
163           rowI = result.list().iterator();
164           loop = true;
165         }
166       }
167     } while (loop);
168     return null;
169   }
170 
171   public void putBack(KeyValue kv) {
172     this.cache = kv;
173   }
174 
175   public void remove() {
176     throw new UnsupportedOperationException("remove not supported");
177   }
178 }