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 /** 24 * Helper class for custom client scanners. 25 */ 26 public abstract class AbstractClientScanner implements ResultScanner { 27 28 @Override 29 public Iterator<Result> iterator() { 30 return new Iterator<Result>() { 31 // The next RowResult, possibly pre-read 32 Result next = null; 33 34 // return true if there is another item pending, false if there isn't. 35 // this method is where the actual advancing takes place, but you need 36 // to call next() to consume it. hasNext() will only advance if there 37 // isn't a pending next(). 38 public boolean hasNext() { 39 if (next == null) { 40 try { 41 next = AbstractClientScanner.this.next(); 42 return next != null; 43 } catch (IOException e) { 44 throw new RuntimeException(e); 45 } 46 } 47 return true; 48 } 49 50 // get the pending next item and advance the iterator. returns null if 51 // there is no next item. 52 public Result next() { 53 // since hasNext() does the real advancing, we call this to determine 54 // if there is a next before proceeding. 55 if (!hasNext()) { 56 return null; 57 } 58 59 // if we get to here, then hasNext() has given us an item to return. 60 // we want to return the item and then null out the next pointer, so 61 // we use a temporary variable. 62 Result temp = next; 63 next = null; 64 return temp; 65 } 66 67 public void remove() { 68 throw new UnsupportedOperationException(); 69 } 70 }; 71 } 72 }