Github user pnowojski commented on a diff in the pull request:
https://github.com/apache/flink/pull/5193#discussion_r159221102
--- Diff:
flink-streaming-java/src/test/java/org/apache/flink/streaming/api/functions/sink/ContentDump.java
---
@@ -0,0 +1,134 @@
+/*
+ * 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.flink.streaming.api.functions.sink;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+import static org.apache.flink.util.Preconditions.checkNotNull;
+import static org.apache.flink.util.Preconditions.checkState;
+
+/**
+ * Utility class to simulate in memory file like writes, flushes and
closing.
+ */
+public class ContentDump {
+ private boolean writable = true;
+ private Map<String, List<String>> filesContent = new HashMap<>();
+
+ public Set<String> listFiles() {
+ return filesContent.keySet();
+ }
+
+ public void setWritable(boolean writable) {
+ this.writable = writable;
+ }
+
+ /**
+ * Creates an empty file.
+ */
+ public ContentWriter createWriter(String name) {
+ checkArgument(!filesContent.containsKey(name), "File [%s]
already exists", name);
+ filesContent.put(name, new ArrayList<>());
+ return new ContentWriter(name, this);
+ }
+
+ public static void move(String name, ContentDump source, ContentDump
target) {
+ Collection<String> content = source.read(name);
+ try (ContentWriter contentWriter = target.createWriter(name)) {
+ contentWriter.write(content).flush();
+ }
+ source.delete(name);
+ }
+
+ public void delete(String name) {
+ filesContent.remove(name);
+ }
+
+ public Collection<String> read(String name) {
+ List<String> content = filesContent.get(name);
+ checkState(content != null, "Unknown file [%s]", name);
+ List<String> result = new ArrayList<>(content);
+ content.clear();
+ return result;
+ }
+
+ private void putContent(String name, List<String> values) {
+ List<String> content = filesContent.get(name);
+ checkState(content != null, "Unknown file [%s]", name);
+ if (!writable) {
+ throw new NotWritableException(name);
+ }
+ content.addAll(values);
+ }
+
+ /**
+ * {@link ContentWriter} represents an abstraction that allows to
putContent to the {@link ContentDump}.
+ */
+ public static class ContentWriter implements AutoCloseable {
+ private final ContentDump contentDump;
+ private final String name;
+ private final List<String> buffer = new ArrayList<>();
+ private boolean closed = false;
+
+ private ContentWriter(String name, ContentDump contentDump) {
+ this.name = checkNotNull(name);
+ this.contentDump = checkNotNull(contentDump);
+ }
+
+ public String getName() {
+ return name;
+ }
+
+ public ContentWriter write(String value) {
+ if (closed) {
+ throw new IllegalStateException();
+ }
+ buffer.add(value);
+ return this;
+ }
+
+ public ContentWriter write(Collection<String> values) {
+ values.forEach(this::write);
+ return this;
+ }
+
+ public ContentWriter flush() {
+ contentDump.putContent(name, buffer);
+ return this;
+ }
+
+ public void close() {
--- End diff --
What do you mean? Close is encouraged to be idempotent.
---
