Github user scubafuchs commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/244#discussion_r112533546
--- Diff:
core/src/main/java/org/apache/accumulo/core/iterators/ServerWrappingIterator.java
---
@@ -0,0 +1,80 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.accumulo.core.iterators;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Map;
+
+import org.apache.accumulo.core.data.ByteSequence;
+import org.apache.accumulo.core.data.Key;
+import org.apache.accumulo.core.data.Range;
+import org.apache.accumulo.core.data.Value;
+
+/**
+ * A convenience class for implementing iterators that select, but do not
modify, entries read from a source iterator. Default implementations exist for
all
+ * methods, but {@link #deepCopy} will throw an
<code>UnsupportedOperationException</code>.
+ *
+ * This iterator has some checks in place to enforce the iterator
contract. Specifically, it verifies that it has a source iterator and that
{@link #seek} has
+ * been called before any data is read. If either of these conditions does
not hold true, an <code>IllegalStateException</code> will be thrown. In
particular,
+ * this means that <code>getSource().seek</code> and
<code>super.seek</code> no longer perform identical actions. Implementors
should take note of this and if
+ * <code>seek</code> is overridden, ensure that <code>super.seek</code> is
called before data is read.
+ */
+public abstract class ServerWrappingIterator implements
SortedKeyValueIterator<Key,Value> {
+
+ protected final SortedKeyValueIterator<Key,Value> source;
+
+ public ServerWrappingIterator(SortedKeyValueIterator<Key,Value> source) {
+ this.source = source;
+ }
+
+ @Override
+ public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment
env) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public Key getTopKey() {
+ return source.getTopKey();
+ }
+
+ @Override
+ public Value getTopValue() {
+ return source.getTopValue();
+ }
+
+ @Override
+ public boolean hasTop() {
+ return source.hasTop();
+ }
+
+ @Override
+ public void init(SortedKeyValueIterator<Key,Value> source,
Map<String,String> options, IteratorEnvironment env) throws IOException {
+ throw new UnsupportedOperationException();
--- End diff --
Same as above -- a bunch of the system iterators don't use or support the
init method, so this is a common implementation.
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