问题描述
hadoop是我的新手，它使用Hadoop 2.6.0版本并尝试解析复杂的XML.搜索了一段时间后，我知道对于XML解析，我们需要编写自定义的InputFormat，它是mahout的XMLInputFormat.我还从此示例
I am new to hadoop, using Hadoop 2.6.0 version and trying to parse an complex XML.After searching for a while I get to know that for XML parsing we need to write custom InputFormat which is mahout's XMLInputFormat.I also took a help from this example
但是当我在passig XMLInputformat类之后运行代码时，如果我使用示例中给出的XMLInputFormat，它将不会调用我自己的Mapper类，并且输出文件中包含0个数据.
But when I am running my code after passig XMLInputformat class, It will not call my own Mapper class and the output file is having 0 data in it if I use the XMLInputFormat given in the example.
令人惊讶的是，如果我没有将XMLInputFormat类传递给我的JOB，则我的映射器可以正常工作并正确输出.请问有人在这里帮助指出我在这里缺少的内容吗?
Surprisingly if I do not pass my XMLInputFormat class to my JOB, then my mapper works fine and giving output properly. Will any one help here to point out what I am missing over here.
我的工作配置类是:
public static void runParserJob(String inputPath, String outputPath) throws IOException {
LOGGER.info("-----runParserJob()-----Start");
Configuration configuration = new Configuration(); configuration.set("xmlinput.start",Constants.XML_INPUT_START_TAG_PRODUCT);
configuration.set("xmlinput.end",Constants.XML_INPUT_END_TAG_PRODUCT);
configuration.set("io.serializations",Constants.XML_IO_SERIALIZATIONS);
Job job = new Job(configuration,Constants.JOB_TITLE);
FileInputFormat.setInputPaths(job, inputPath);
job.setJarByClass(ParserDriver.class);
job.setMapperClass(XMLMapper.class);
job.setNumReduceTasks(0);
job.setInputFormatClass(XmlInputFormat.class);
job.setOutputKeyClass(NullWritable.class);
job.setOutputValueClass(Text.class);
Path hdfsOutputPath = new Path(outputPath);
FileOutputFormat.setOutputPath(job, hdfsOutputPath);
FileSystem dfs = FileSystem.get(hdfsOutputPath.toUri(),configuration);
/**Using this condition it will create output at same location
* by deleting older data in that location**/
if(dfs.exists(hdfsOutputPath)){
dfs.delete(hdfsOutputPath,true);
}
try{
job.waitForCompletion(true);
}catch(InterruptedException ie){
LOGGER.error("-----Process interrupted in between Exception-----", ie);
}catch(ClassNotFoundException ce){
LOGGER.error("-----Class not found while running the job-----",ce);
}
}
我的XMLInputFormat类为:
public class XmlInputFormat extends TextInputFormat{
public static final String START_TAG_KEY = "xmlinput.start";
public static final String END_TAG_KEY = "xmlinput.end";
@Override
public RecordReader<LongWritable,Text> createRecordReader(InputSplit is, TaskAttemptContext tac) {
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 inputSplit, TaskAttemptContext taskAttemptContext)
throws IOException, InterruptedException {
FileSplit fileSplit = (FileSplit)inputSplit;
startTag = taskAttemptContext.getConfiguration().get(START_TAG_KEY).getBytes("utf-8");
endTag = taskAttemptContext.getConfiguration().get(END_TAG_KEY).getBytes("utf-8");
start = fileSplit.getStart();
end = start + fileSplit.getLength();
Path file = fileSplit.getPath();
FileSystem hdfs = file.getFileSystem(taskAttemptContext.getConfiguration());
fsin = hdfs.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 void close() throws IOException {
}
@Override
public LongWritable getCurrentKey() throws IOException,InterruptedException {
return null;
}
@Override
public Text getCurrentValue() throws IOException, InterruptedException {
return null;
}
@Override
public float getProgress() throws IOException, InterruptedException {
return 0;
}
private boolean readUntilMatch(byte[] match, boolean withinBlock) throws IOException{
int i = 0;
while(true){
int b = fsin.read();
//If reaches to EOF
if(b == -1){
return false;
}
//If not then save into the buffer.
if(withinBlock){
buffer.write(b);
}
// check if we're matching:
if (b == match[i]) {
i++;
if (i >= match.length) return true;
} else i = 0;
// see if we've passed the stop point:
if (!withinBlock && i == 0 && fsin.getPos() >= end) return false;
}
}
}
}
有人可以帮我吗?提前致谢.如果我在任何地方出错了，请纠正我.
Can any one help me out here? Thanks in advance. Correct me if I am going wrong anywhere.
推荐答案
我不确定您的XML结构如何，但是例如，如果您具有XML结构:
I am not sure how your XML structure looks like, but for example if you have a XML structure:
<data>
<product id="101" itemCategory="BER" transaction="PUR">
<transaction-id>102A5RET</transaction-id>
<item-name>Blue-Moon-12-PK-BTTLE</item-name>
<item-purchased>2</item-purchased>
<item-price>12.99</item-price>
<time-stamp>2015-04-20 11:12:13 102301</time-stamp>
</product>
.
.
.
</data>
您的XMLInputFormat类将需要知道您要使用哪个XML节点:
Your XMLInputFormat class would need to know which XML node you want to work with:
configuration.set("xmlinput.start", "<product") //note only <product
configuration.set("xmlinput.end", "</product>") //note only </product>
希望这会有所帮助！
这篇关于使用XMLInputFormat解析hadoop中的xml时不执行我的hadoop映射器类的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！