[SPARK-16114][SQL] structured streaming network word count examples

## What changes were proposed in this pull request?

Network word count example for structured streaming

## How was this patch tested?

Run locally

Author: James Thomas <jamesjoethomas@gmail.com>
Author: James Thomas <jamesthomas@Jamess-MacBook-Pro.local>

Closes #13816 from jjthomas/master.

1 files changed, 82 insertions, 0 deletions

diff --git a/examples/src/main/java/org/apache/spark/examples/sql/streaming/JavaStructuredNetworkWordCount.java b/examples/src/main/java/org/apache/spark/examples/sql/streaming/JavaStructuredNetworkWordCount.java
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@@ -0,0 +1,82 @@
+/*
+ * 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.spark.examples.sql.streaming;
+
+import org.apache.spark.api.java.function.FlatMapFunction;
+import org.apache.spark.sql.*;
+import org.apache.spark.sql.streaming.StreamingQuery;
+
+import java.util.Arrays;
+import java.util.Iterator;
+
+/**
+ * Counts words in UTF8 encoded, '\n' delimited text received from the network every second.
+ *
+ * Usage: JavaStructuredNetworkWordCount <hostname> <port>
+ * <hostname> and <port> describe the TCP server that Structured Streaming
+ * would connect to receive data.
+ *
+ * To run this on your local machine, you need to first run a Netcat server
+ *    `$ nc -lk 9999`
+ * and then run the example
+ *    `$ bin/run-example sql.streaming.JavaStructuredNetworkWordCount
+ *    localhost 9999`
+ */
+public final class JavaStructuredNetworkWordCount {
+
+  public static void main(String[] args) throws Exception {
+    if (args.length < 2) {
+      System.err.println("Usage: JavaNetworkWordCount <hostname> <port>");
+      System.exit(1);
+    }
+
+    String host = args[0];
+    int port = Integer.parseInt(args[1]);
+
+    SparkSession spark = SparkSession
+      .builder()
+      .appName("JavaStructuredNetworkWordCount")
+      .getOrCreate();
+
+    // Create DataFrame representing the stream of input lines from connection to host:port
+    Dataset<String> lines = spark
+      .readStream()
+      .format("socket")
+      .option("host", host)
+      .option("port", port)
+      .load().as(Encoders.STRING());
+
+    // Split the lines into words
+    Dataset<String> words = lines.flatMap(new FlatMapFunction<String, String>() {
+      @Override
+      public Iterator<String> call(String x) {
+        return Arrays.asList(x.split(" ")).iterator();
+      }
+    }, Encoders.STRING());
+
+    // Generate running word count
+    Dataset<Row> wordCounts = words.groupBy("value").count();
+
+    // Start running the query that prints the running counts to the console
+    StreamingQuery query = wordCounts.writeStream()
+      .outputMode("complete")
+      .format("console")
+      .start();
+
+    query.awaitTermination();
+  }
+}