Github user kl0u commented on a diff in the pull request:
https://github.com/apache/flink/pull/3484#discussion_r106162497
--- Diff:
flink-examples/flink-examples-streaming/src/main/java/org/apache/flink/streaming/examples/sideoutput/SideOutputExample.java
---
@@ -0,0 +1,139 @@
+/*
+ * 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.examples.sideoutput;
+
+import org.apache.flink.api.java.functions.KeySelector;
+import org.apache.flink.streaming.api.TimeCharacteristic;
+import
org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
+import org.apache.flink.streaming.api.functions.ProcessFunction;
+import
org.apache.flink.streaming.api.windowing.assigners.TumblingEventTimeWindows;
+import org.apache.flink.streaming.api.windowing.time.Time;
+import org.apache.flink.util.OutputTag;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.utils.ParameterTool;
+import org.apache.flink.examples.java.wordcount.util.WordCountData;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import
org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.util.Collector;
+
+/**
+ * An example that illustrates the use of side outputs.
+ *
+ * <p>This is a modified version of {@link
org.apache.flink.streaming.examples.windowing.WindowWordCount}
+ * that has a filter in the tokenizer and only emits some words for
counting
+ * while emitting the other words to a side output.
+ */
+public class SideOutputExample {
+
+ /**
+ * We need to create an {@link OutputTag} so that we can reference it
when emitting
+ * data to a side output and also to retrieve the side output stream
from an operation.
+ */
+ static final OutputTag<String> rejectedWordsTag = new
OutputTag<String>("rejected") {};
--- End diff --
Here we add a side output but we do nothing to show that it works. Probably
we can add a prefix "rejected-" to the record and print it, so that the user
can see what the side output does.
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