Accesing file in Mapper through Distributed Cache - hadoop

Question

I want to access the contents of the distributed file in my Mapper. Below is the code I have written which generates the name of the file for Distributed Cache. Please help me accessing the contents of the file
public class DistCacheExampleMapper extends MapReduceBase implements Mapper<LongWritable, Text, Text, Text >
{
Text a = new Text();
Path[] dates = new Path[0];
public void configure(JobConf conf) {
try {
dates = DistributedCache.getLocalCacheFiles(conf);
String astr = dates.toString();
a = new Text(astr);
} catch (IOException ioe) {
System.err.println("Caught exception while getting cached files: " +
StringUtils.stringifyException(ioe));
}
}
#Override
public void map(LongWritable key, Text value, OutputCollector<Text, Text> output,
Reporter reporter) throws IOException {
String line = value.toString();
for(Path cacheFile: dates){
output.collect(new Text(line), new Text(cacheFile.getName()));
}
}
}

Answer 1

Try this instead in your configure() method:
List<String []> lines;
Path[] files = new Path[0];
public void configure(JobConf conf) {
lines = new ArrayList<>();
BufferedReader SW;
try {
files = DistributedCache.getLocalCacheFiles(conf);
SW = new BufferedReader(new FileReader(files[0].toString()));
String line;
while ((line = SW.readLine()) != null) {
lines.add(line.split(",")); //now, each lines entry is a String array, with each element being a column
}
SW.close();
} catch (IOException ioe) {
System.err.println("Caught exception while getting cached files: " +
StringUtils.stringifyException(ioe));
}
}
This way, you will have the contents of the files (in this case the first file) in the Distributed Cache, in the variable lines. Each lines entry represent a String array, which is split by ','. So the first column of the first row is lines.get(0)[0], the third row of the second line is lines.get(1)[2], etc.