1 /** 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 package org.apache.hadoop.hbase.client; 19 20 import java.io.IOException; 21 import java.util.Iterator; 22 23 import org.apache.hadoop.classification.InterfaceAudience; 24 25 /** 26 * Helper class for custom client scanners. 27 */ 28 @InterfaceAudience.Private 29 public abstract class AbstractClientScanner implements ResultScanner { 30 31 @Override 32 public Iterator<Result> iterator() { 33 return new Iterator<Result>() { 34 // The next RowResult, possibly pre-read 35 Result next = null; 36 37 // return true if there is another item pending, false if there isn't. 38 // this method is where the actual advancing takes place, but you need 39 // to call next() to consume it. hasNext() will only advance if there 40 // isn't a pending next(). 41 public boolean hasNext() { 42 if (next == null) { 43 try { 44 next = AbstractClientScanner.this.next(); 45 return next != null; 46 } catch (IOException e) { 47 throw new RuntimeException(e); 48 } 49 } 50 return true; 51 } 52 53 // get the pending next item and advance the iterator. returns null if 54 // there is no next item. 55 public Result next() { 56 // since hasNext() does the real advancing, we call this to determine 57 // if there is a next before proceeding. 58 if (!hasNext()) { 59 return null; 60 } 61 62 // if we get to here, then hasNext() has given us an item to return. 63 // we want to return the item and then null out the next pointer, so 64 // we use a temporary variable. 65 Result temp = next; 66 next = null; 67 return temp; 68 } 69 70 public void remove() { 71 throw new UnsupportedOperationException(); 72 } 73 }; 74 } 75 }