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Both sides previous revision Previous revision 2012/01/31 11:47 straka 2012/01/31 11:43 straka 2012/01/31 11:42 straka 2012/01/31 11:39 straka 2012/01/31 11:29 straka 2012/01/31 11:28 straka 2012/01/31 11:27 straka 2012/01/31 09:52 straka Change Java commandline syntax.2012/01/30 15:38 majlis 2012/01/30 15:04 majlis 2012/01/28 17:55 straka 2012/01/27 23:57 straka 2012/01/27 23:48 straka 2012/01/27 23:47 straka 2012/01/27 23:46 straka 2012/01/27 22:20 straka 2012/01/27 22:17 straka 2012/01/27 22:17 straka 2012/01/27 22:16 straka 2012/01/27 22:16 straka 2012/01/27 22:08 straka 2012/01/27 22:08 straka 2012/01/27 22:01 straka 2012/01/27 21:56 straka 2012/01/27 21:52 straka 2012/01/27 21:47 straka 2012/01/27 21:41 straka 2012/01/27 21:32 straka 2012/01/27 21:28 straka 2012/01/27 21:28 straka 2012/01/27 21:27 straka 2012/01/27 21:27 straka 2012/01/27 21:02 straka 2012/01/27 21:01 straka 2012/01/27 20:56 straka 2012/01/27 20:40 straka 2012/01/27 20:11 straka vytvořeno Go		2012/01/31 11:47 straka 2012/01/31 11:43 straka 2012/01/31 11:42 straka 2012/01/31 11:39 straka 2012/01/31 11:29 straka 2012/01/31 11:28 straka 2012/01/31 11:27 straka 2012/01/31 09:52 straka Change Java commandline syntax.2012/01/30 15:38 majlis 2012/01/30 15:04 majlis 2012/01/28 17:55 straka 2012/01/27 23:57 straka 2012/01/27 23:48 straka 2012/01/27 23:47 straka 2012/01/27 23:46 straka 2012/01/27 22:20 straka 2012/01/27 22:17 straka 2012/01/27 22:17 straka 2012/01/27 22:16 straka 2012/01/27 22:16 straka 2012/01/27 22:08 straka 2012/01/27 22:08 straka 2012/01/27 22:01 straka 2012/01/27 21:56 straka 2012/01/27 21:52 straka 2012/01/27 21:47 straka 2012/01/27 21:41 straka 2012/01/27 21:32 straka 2012/01/27 21:28 straka 2012/01/27 21:28 straka 2012/01/27 21:27 straka 2012/01/27 21:27 straka 2012/01/27 21:02 straka 2012/01/27 21:01 straka 2012/01/27 20:56 straka 2012/01/27 20:40 straka 2012/01/27 20:11 straka vytvořeno Go Next revision Both sides next revision
courses:mapreduce-tutorial:step-24 [2012/01/27 21:41] straka		courses:mapreduce-tutorial:step-24 [2012/01/27 21:47] straka
Line 3:		Line 3:
	We start by going through a simple Hadoop job with Mapper only.		We start by going through a simple Hadoop job with Mapper only.
-	A mapper which processes (key, value) pairs of types (Kin, Vin) and produces (key, value) pairs of types (Kout, Vout) must be a subclass of [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapreduce/Mapper.html|Mapper<Kin, Vin, Kout, Vout>]]. In our case, ''TheMapper'' is subclass of ''Mapper<Text, Text, Text, Text>''.	+	A mapper which processes (key, value) pairs of types (Kin, Vin) and produces (key, value) pairs of types (Kout, Vout) must be a subclass of [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapreduce/Mapper.html|Mapper<Kin, Vin, Kout, Vout>]]. In our case, the mapper is subclass of ''Mapper<Text, Text, Text, Text>''.
		+	The mapper must define a ''map'' method and may provide ''setup'' and ''context'' method:
		+	<code java>
		+	public static class TheMapper extends Mapper<Text, Text, Text, Text>{
		+	public void setup(Context context) throws IOException, InterruptedException {}
-	http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapreduce/Mapper.html	+	public void map(Text key, Text value, Context context) throws IOException, InterruptedException {}
-	The Mapper outputs only keys starting with ''A''.	+	public void cleanup(Context context) throws IOException, InterruptedException {}
		+	}
		+	</code>
		+
		+	Outputting (key, value) pairs is performed using the [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapreduce/MapContext.html|MapContext<Kin, Vin, Kout, Vout>]] (the ''Context'' is an abbreviation for this type).
	<file java MapperOnlyHadoopJob.java>		<file java MapperOnlyHadoopJob.java>

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