/*** * @author YangXin * @info Mapper选择艺术家的整数特征ID然后建立单个特征的向量。这些一维的部分 * 向量会传给Reducer，后者会将这些向量简单地进行联结。生成一个完整的向量。

*/ package unitTwelve; import java.io.IOException; import java.util.HashMap; import java.util.Map; import java.util.regex.Pattern; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.io.DefaultStringifier; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.util.GenericsUtil; import org.apache.mahout.math.NamedVector; import org.apache.mahout.math.SequentialAccessSparseVector; import org.apache.mahout.math.VectorWritable; public class VectorMapper extends Mapper<LongWritable, Text, Text, VectorWritable>{ private Pattern splitter; private VectorWritable writer; private Map<String, Integer> dictionary = new HashMap<String, Integer>(); @Override protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException{ String[] fields = splitter.split(value.toString()); if(fields.length < 4){ context.getCounter("Map", "LinesWithErrors").increment(1); return; } String arrtist = fields[1]; String tag = fields[2]; double weight = Double.parseDouble(fields[3]); NamedVector vector = new NamedVector(new SequentialAccessSparseVector(dictionary.size()), tag); vector.set(dictionary.get(value), weight); writer.set(vector); context.write(new Text(tag), writer); } @Override protected void setup(Context context) throws IOException, InterruptedException{ super.setup(context); Configuration conf = context.getConfiguration(); DefaultStringifier<Map<String, Integer>> mapStringifier = new DefaultStringifier<Map<String, Integer>>(conf, GenericsUtil.getClass(dictionary)); dictionary = mapStringifier.fromString(conf.get("dictionary")); splitter = Pattern.compile("<sep>"); writer = new VectorWritable(); } } </span></strong>