[SPARK-16312][FOLLOW-UP][STREAMING][KAFKA][DOC] Add java code snippet for...

[SPARK-16312][FOLLOW-UP][STREAMING][KAFKA][DOC] Add java code snippet for Kafka 0.10 integration doc

## What changes were proposed in this pull request?

added java code snippet for Kafka 0.10 integration doc

## How was this patch tested?

SKIP_API=1 jekyll build

## Screenshot

![kafka-doc](https://cloud.githubusercontent.com/assets/15843379/19826272/bf0d8a4c-9db8-11e6-9e40-1396723df4bc.png)

Author: Liwei Lin <lwlin7@gmail.com>

Closes #15679 from lw-lin/kafka-010-examples.

docs/streaming-kafka-0-10-integration.md

@@ -8,9 +8,9 @@ The Spark Streaming integration for Kafka 0.10 is similar in design to the 0.8 [
 ### Linking
 For Scala/Java applications using SBT/Maven project definitions, link your streaming application with the following artifact (see [Linking section](streaming-programming-guide.html#linking) in the main programming guide for further information).
 
-		groupId = org.apache.spark
-		artifactId = spark-streaming-kafka-0-10_{{site.SCALA_BINARY_VERSION}}
-		version = {{site.SPARK_VERSION_SHORT}}
+	groupId = org.apache.spark
+	artifactId = spark-streaming-kafka-0-10_{{site.SCALA_BINARY_VERSION}}
+	version = {{site.SPARK_VERSION_SHORT}}
 
 ### Creating a Direct Stream
  Note that the namespace for the import includes the version, org.apache.spark.streaming.kafka010
@@ -44,6 +44,42 @@ For Scala/Java applications using SBT/Maven project definitions, link your strea
 Each item in the stream is a [ConsumerRecord](http://kafka.apache.org/0100/javadoc/org/apache/kafka/clients/consumer/ConsumerRecord.html)
 </div>
 <div data-lang="java" markdown="1">
+	import java.util.*;
+	import org.apache.spark.SparkConf;
+	import org.apache.spark.TaskContext;
+	import org.apache.spark.api.java.*;
+	import org.apache.spark.api.java.function.*;
+	import org.apache.spark.streaming.api.java.*;
+	import org.apache.spark.streaming.kafka010.*;
+	import org.apache.kafka.clients.consumer.ConsumerRecord;
+	import org.apache.kafka.common.TopicPartition;
+	import org.apache.kafka.common.serialization.StringDeserializer;
+	import scala.Tuple2;
+	
+	Map<String, Object> kafkaParams = new HashMap<>();
+	kafkaParams.put("bootstrap.servers", "localhost:9092,anotherhost:9092");
+	kafkaParams.put("key.deserializer", StringDeserializer.class);
+	kafkaParams.put("value.deserializer", StringDeserializer.class);
+	kafkaParams.put("group.id", "use_a_separate_group_id_for_each_stream");
+	kafkaParams.put("auto.offset.reset", "latest");
+	kafkaParams.put("enable.auto.commit", false);
+	
+	Collection<String> topics = Arrays.asList("topicA", "topicB");
+	
+	final JavaInputDStream<ConsumerRecord<String, String>> stream =
+	  KafkaUtils.createDirectStream(
+	    streamingContext,
+	    LocationStrategies.PreferConsistent(),
+	    ConsumerStrategies.<String, String>Subscribe(topics, kafkaParams)
+	  );
+	
+	stream.mapToPair(
+	  new PairFunction<ConsumerRecord<String, String>, String, String>() {
+	    @Override
+	    public Tuple2<String, String> call(ConsumerRecord<String, String> record) {
+	      return new Tuple2<>(record.key(), record.value());
+	    }
+	  })
 </div>
 </div>
 
@@ -85,6 +121,20 @@ If you have a use case that is better suited to batch processing, you can create
 
 </div>
 <div data-lang="java" markdown="1">
+	// Import dependencies and create kafka params as in Create Direct Stream above
+
+	OffsetRange[] offsetRanges = {
+	  // topic, partition, inclusive starting offset, exclusive ending offset
+	  OffsetRange.create("test", 0, 0, 100),
+	  OffsetRange.create("test", 1, 0, 100)
+	};
+
+	JavaRDD<ConsumerRecord<String, String>> rdd = KafkaUtils.createRDD(
+	  sparkContext,
+	  kafkaParams,
+	  offsetRanges,
+	  LocationStrategies.PreferConsistent()
+	);
 </div>
 </div>
 
@@ -103,6 +153,20 @@ Note that you cannot use `PreferBrokers`, because without the stream there is no
 	}
 </div>
 <div data-lang="java" markdown="1">
+	stream.foreachRDD(new VoidFunction<JavaRDD<ConsumerRecord<String, String>>>() {
+	  @Override
+	  public void call(JavaRDD<ConsumerRecord<String, String>> rdd) {
+	    final OffsetRange[] offsetRanges = ((HasOffsetRanges) rdd.rdd()).offsetRanges();
+	    rdd.foreachPartition(new VoidFunction<Iterator<ConsumerRecord<String, String>>>() {
+	      @Override
+	      public void call(Iterator<ConsumerRecord<String, String>> consumerRecords) {
+	        OffsetRange o = offsetRanges[TaskContext.get().partitionId()];
+	        System.out.println(
+	          o.topic() + " " + o.partition() + " " + o.fromOffset() + " " + o.untilOffset());
+	      }
+	    });
+	  }
+	});
 </div>
 </div>
 
@@ -120,15 +184,24 @@ Kafka has an offset commit API that stores offsets in a special Kafka topic.  By
 <div class="codetabs">
 <div data-lang="scala" markdown="1">
 	stream.foreachRDD { rdd =>
-	  val offsets = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
+	  val offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
 
 	  // some time later, after outputs have completed
-	  stream.asInstanceOf[CanCommitOffsets].commitAsync(offsets)
+	  stream.asInstanceOf[CanCommitOffsets].commitAsync(offsetRanges)
 	}
 
 As with HasOffsetRanges, the cast to CanCommitOffsets will only succeed if called on the result of createDirectStream, not after transformations.  The commitAsync call is threadsafe, but must occur after outputs if you want meaningful semantics.
 </div>
 <div data-lang="java" markdown="1">
+	stream.foreachRDD(new VoidFunction<JavaRDD<ConsumerRecord<String, String>>>() {
+	  @Override
+	  public void call(JavaRDD<ConsumerRecord<String, String>> rdd) {
+	    OffsetRange[] offsetRanges = ((HasOffsetRanges) rdd.rdd()).offsetRanges();
+
+	    // some time later, after outputs have completed
+	    ((CanCommitOffsets) stream.inputDStream()).commitAsync(offsetRanges);
+	  }
+	});
 </div>
 </div>
 
@@ -141,7 +214,7 @@ For data stores that support transactions, saving offsets in the same transactio
 
 	// begin from the the offsets committed to the database
 	val fromOffsets = selectOffsetsFromYourDatabase.map { resultSet =>
-	  new TopicPartition(resultSet.string("topic")), resultSet.int("partition")) -> resultSet.long("offset")
+	  new TopicPartition(resultSet.string("topic"), resultSet.int("partition")) -> resultSet.long("offset")
 	}.toMap
 
 	val stream = KafkaUtils.createDirectStream[String, String](
@@ -155,16 +228,46 @@ For data stores that support transactions, saving offsets in the same transactio
 
 	  val results = yourCalculation(rdd)
 
-	  yourTransactionBlock {
-	    // update results
+	  // begin your transaction
 
-	    // update offsets where the end of existing offsets matches the beginning of this batch of offsets
+	  // update results
+	  // update offsets where the end of existing offsets matches the beginning of this batch of offsets
+	  // assert that offsets were updated correctly
 
-	    // assert that offsets were updated correctly
-	  }
+	  // end your transaction
 	}
 </div>
 <div data-lang="java" markdown="1">
+	// The details depend on your data store, but the general idea looks like this
+
+	// begin from the the offsets committed to the database
+	Map<TopicPartition, Long> fromOffsets = new HashMap<>();
+	for (resultSet : selectOffsetsFromYourDatabase)
+	  fromOffsets.put(new TopicPartition(resultSet.string("topic"), resultSet.int("partition")), resultSet.long("offset"));
+	}
+
+	JavaInputDStream<ConsumerRecord<String, String>> stream = KafkaUtils.createDirectStream(
+	  streamingContext,
+	  LocationStrategies.PreferConsistent(),
+	  ConsumerStrategies.<String, String>Assign(fromOffsets.keySet(), kafkaParams, fromOffsets)
+	);
+
+	stream.foreachRDD(new VoidFunction<JavaRDD<ConsumerRecord<String, String>>>() {
+	  @Override
+	  public void call(JavaRDD<ConsumerRecord<String, String>> rdd) {
+	    OffsetRange[] offsetRanges = ((HasOffsetRanges) rdd.rdd()).offsetRanges();
+	    
+	    Object results = yourCalculation(rdd);
+
+	    // begin your transaction
+
+	    // update results
+	    // update offsets where the end of existing offsets matches the beginning of this batch of offsets
+	    // assert that offsets were updated correctly
+
+	    // end your transaction
+	  }
+	});
 </div>
 </div>
 
@@ -185,6 +288,14 @@ The new Kafka consumer [supports SSL](http://kafka.apache.org/documentation.html
 	)
 </div>
 <div data-lang="java" markdown="1">
+	Map<String, Object> kafkaParams = new HashMap<String, Object>();
+	// the usual params, make sure to change the port in bootstrap.servers if 9092 is not TLS
+	kafkaParams.put("security.protocol", "SSL");
+	kafkaParams.put("ssl.truststore.location", "/some-directory/kafka.client.truststore.jks");
+	kafkaParams.put("ssl.truststore.password", "test1234");
+	kafkaParams.put("ssl.keystore.location", "/some-directory/kafka.client.keystore.jks");
+	kafkaParams.put("ssl.keystore.password", "test1234");
+	kafkaParams.put("ssl.key.password", "test1234");
 </div>
 </div>