import java.io.IOException;
import java.util.List;
import org.apache.hadoop.fs.BlockLocation;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DataOutputBuffer;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
public class XmlInputFormat extends TextInputFormat {
public static final String START_TAG_KEY = "< student>";
public static final String END_TAG_KEY = "</student>";
@Override
public RecordReader<LongWritable, Text> createRecordReader(
InputSplit split, TaskAttemptContext context) {
return new XmlRecordReader();
}
public static class XmlRecordReader extends
RecordReader<LongWritable, Text> {
private byte[] startTag;
private byte[] endTag;
private long start;
private long end;
private FSDataInputStream fsin;
private DataOutputBuffer buffer = new DataOutputBuffer();
private LongWritable key = new LongWritable();
private Text value = new Text();
@Override
public void initialize(InputSplit is, TaskAttemptContext tac)
throws IOException, InterruptedException {
FileSplit fileSplit = (FileSplit) is;
String START_TAG_KEY = "<employee>";
String END_TAG_KEY = "</employee>";
startTag = START_TAG_KEY.getBytes("utf-8");
endTag = END_TAG_KEY.getBytes("utf-8");
start = fileSplit.getStart();
end = start + fileSplit.getLength();
Path file = fileSplit.getPath();
FileSystem fs =file.getFileSystem(tac.getConfiguration());
fsin = fs.open(fileSplit.getPath());
fsin.seek(start);
}
@Override
public boolean nextKeyValue() throws
IOException,InterruptedException {
if (fsin.getPos() < end) {
if (readUntilMatch(startTag, false)) {
try {
buffer.write(startTag);
if (readUntilMatch(endTag, true)) {
value.set(buffer.getData(), 0,
buffer.getLength());
key.set(fsin.getPos());
return true;
}
} finally {
buffer.reset();
}
}
}
return false;
}
@Override
public LongWritable getCurrentKey() throws IOException,
InterruptedException {
return key;
}
@Override
public Text getCurrentValue() throws IOException,
InterruptedException {
return value;
}
@Override
public float getProgress() throws IOException,
InterruptedException {
return (fsin.getPos() - start) / (float) (end - start);
}
@Override
public void close() throws IOException {
fsin.close();
}
private boolean readUntilMatch(byte[] match, boolean
withinBlock)throws IOException {
int i = 0;
while (true) {
int b = fsin.read();
if (b == -1)
return false;
if (withinBlock)
buffer.write(b);
if (b == match[i]) {
i++;
if (i >= match.length)
return true;
} else
i = 0;
if (!withinBlock && i == 0 && fsin.getPos() >= end)
return false;
}
}
}
}