这是我的源代码
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.SequenceFileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
public class PageRank {
public static final String MAGIC_STRING = ">>>>";
boolean overwrite = true;
PageRank(boolean overwrite){
this.overwrite = overwrite;
}
public static class TextPair implements WritableComparable<TextPair>{
Text x;
int ordering;
public TextPair(){
x = new Text();
ordering = 1;
}
public void setText(Text t, int o){
x = t;
ordering = o;
}
public void setText(String t, int o){
x.set(t);
ordering = o;
}
public void readFields(DataInput in) throws IOException {
x.readFields(in);
ordering = in.readInt();
}
public void write(DataOutput out) throws IOException {
x.write(out);
out.writeInt(ordering);
}
public int hashCode() {
return x.hashCode();
}
public int compareTo(TextPair o) {
int x = this.x.compareTo(o.x);
if(x==0)
return ordering-o.ordering;
else
return x;
}
}
public static class MapperA extends Mapper<LongWritable, Text, TextPair, Text> {
private Text word = new Text();
Text title = new Text();
Text link = new Text();
TextPair textpair = new TextPair();
boolean start=false;
String currentTitle="";
private Pattern linkPattern = Pattern.compile("\\[\\[\\s*(.+?)\\s*\\]\\]");
private Pattern titlePattern = Pattern.compile("<title>\\s*(.+?)\\s*</title>");
private Pattern pagePattern = Pattern.compile("<page>\\s*(.+?)\\s*</page>");
public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
String line = value.toString();
int startPage=line.lastIndexOf("<title>");
if(startPage<0)
{
Matcher matcher = linkPattern.matcher(line);
int n = 0;
title.set(currentTitle);
while(matcher.find()){
textpair.setText(matcher.group(1), 1);
context.write(textpair, title);
}
link.set(MAGIC_STRING);
textpair.setText(title.toString(), 0);
context.write(textpair, link);
}
else
{
String result=line.trim();
Matcher titleMatcher = titlePattern.matcher(result);
if(titleMatcher.find()){
currentTitle = titleMatcher.group(1);
}
else
{
currentTitle=result;
}
}
}
}
public static class ReducerA extends Reducer<TextPair, Text, Text, Text>{
Text aw = new Text();
boolean valid = false;
String last = "";
public void run(Context context) throws IOException, InterruptedException {
setup(context);
while (context.nextKeyValue()) {
TextPair key = context.getCurrentKey();
Text value = context.getCurrentValue();
if(key.ordering==0){
last = key.x.toString();
}
else if(key.x.toString().equals(last)){
context.write(key.x, value);
}
}
cleanup(context);
}
}
public static class MapperB extends Mapper<Text, Text, Text, Text>{
Text t = new Text();
public void map(Text key, Text value, Context context) throws InterruptedException, IOException{
context.write(value, key);
}
}
public static class ReducerB extends Reducer<Text, Text, Text, PageRankRecord>{
ArrayList<String> q = new ArrayList<String>();
public void reduce(Text key, Iterable<Text> values, Context context)throws InterruptedException, IOException{
q.clear();
for(Text value:values){
q.add(value.toString());
}
PageRankRecord prr = new PageRankRecord();
prr.setPageRank(1.0);
if(q.size()>0){
String[] a = new String[q.size()];
q.toArray(a);
prr.setlinks(a);
}
context.write(key, prr);
}
}
public boolean roundA(Configuration conf, String inputPath, String outputPath, boolean overwrite) throws IOException, InterruptedException, ClassNotFoundException{
if(FileSystem.get(conf).exists(new Path(outputPath))){
if(overwrite){
FileSystem.get(conf).delete(new Path(outputPath), true);
System.err.println("The target file is dirty, overwriting!");
}
else
return true;
}
Job job = new Job(conf, "closure graph build round A");
//job.setJarByClass(GraphBuilder.class);
job.setMapperClass(MapperA.class);
//job.setCombinerClass(RankCombiner.class);
job.setReducerClass(ReducerA.class);
job.setMapOutputKeyClass(TextPair.class);
job.setMapOutputValueClass(Text.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(Text.class);
job.setOutputFormatClass(SequenceFileOutputFormat.class);
job.setNumReduceTasks(30);
FileInputFormat.addInputPath(job, new Path(inputPath));
SequenceFileOutputFormat.setOutputPath(job, new Path(outputPath));
return job.waitForCompletion(true);
}
public boolean roundB(Configuration conf, String inputPath, String outputPath) throws IOException, InterruptedException, ClassNotFoundException{
if(FileSystem.get(conf).exists(new Path(outputPath))){
if(overwrite){
FileSystem.get(conf).delete(new Path(outputPath), true);
System.err.println("The target file is dirty, overwriting!");
}
else
return true;
}
Job job = new Job(conf, "closure graph build round B");
//job.setJarByClass(PageRank.class);
job.setMapperClass(MapperB.class);
//job.setCombinerClass(RankCombiner.class);
job.setReducerClass(ReducerB.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(Text.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(PageRankRecord.class);
job.setInputFormatClass(SequenceFileInputFormat.class);
job.setOutputFormatClass(SequenceFileOutputFormat.class);
job.setNumReduceTasks(30);
SequenceFileInputFormat.addInputPath(job, new Path(inputPath));
SequenceFileOutputFormat.setOutputPath(job, new Path(outputPath));
return job.waitForCompletion(true);
}
public boolean build(Configuration conf, String inputPath, String outputPath) throws IOException, InterruptedException, ClassNotFoundException{
System.err.println(inputPath);
if(roundA(conf, inputPath, "cgb", true)){
return roundB(conf, "cgb", outputPath);
}
else
return false;
}
public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException{
Configuration conf = new Configuration();
//PageRanking.banner("ClosureGraphBuilder");
PageRank cgb = new PageRank(true);
cgb.build(conf, args[0], args[1]);
}
}
这是我如何编译和运行
javac -classpath hadoop-0.20.1-core.jar -d pagerank_classes PageRank.java PageRankRecord.java
jar -cvf pagerank.jar -C pagerank_classes/ .
bin/hadoop jar pagerank.jar PageRank pagerank result
但我收到以下错误：
INFO mapred.JobClient: Task Id : attempt_201001012025_0009_m_000001_0, Status : FAILED
java.lang.RuntimeException: java.lang.ClassNotFoundException: PageRank$MapperA
有人能告诉我什么是错的
由于
答案 0 :(得分：7)
如果您使用的是0.2.0 hadoop（想要使用未弃用的类），您可以这样做：
public int run(String[] args) throws Exception {
Job job = new Job();
job.setJarByClass(YourMapReduceClass.class); // <-- omitting this causes above error
job.setMapperClass(MyMapper.class);
FileInputFormat.setInputPaths(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.waitForCompletion(true);
return 0;
}
答案 1 :(得分：1)
“PageRank $ MapperA.class”最终是否在该jar文件中？它应该与“PageRank.class”在同一个地方。
答案 2 :(得分：1)
尝试添加“--libjars pagerank.jar”。 Mapper和reducer在机器上运行，因此您需要将jar分配给每台机器。 “--libjars”有助于做到这一点。
答案 3 :(得分：1)
对于HADOOP_CLASSPATH，您应该指定JAR文件所在的文件夹...
如果您想了解类路径的工作原理：http://download.oracle.com/javase/6/docs/technotes/tools/windows/classpath.html
答案 4 :(得分：0)
我想你应该更改你的HADOOP_CLASSPATH变量，以便它指向jar文件。
e.g。 HADOOP_CLASSPATH=<what ever the path>/PageRank.jar或类似的东西。
答案 5 :(得分：0)
如果您使用ECLIPSE生成jar，请使用“将生成的库提取到生成的JAR”选项。
答案 6 :(得分：0)
虽然MapReduce程序是并行处理。 Mapper，Combiner和Reducer类具有序列流。必须等待完成每个流程依赖于其他类所以需要job.waitForCompletion(true);但是必须在启动Mapper，Combiner和Reducer类之前设置输入和输出路径。 Reference