我的映射器和缩减器如下。但是我遇到了一些奇怪的异常。 我不明白为什么会抛出这种异常。
public static class MyMapper implements Mapper<LongWritable, Text, Text, Info> {
@Override
public void map(LongWritable key, Text value,
OutputCollector<Text, Info> output, Reporter reporter)
throws IOException {
Text text = new Text("someText")
//process
output.collect(text, infoObjeject);
}
}
public static class MyReducer implements Reducer<Text, Info, Text, Text> {
@Override
public void reduce(Text key, Iterator<Info> values,
OutputCollector<Text, Text> output, Reporter reporter)
throws IOException {
String value = "xyz" //derived in some way
//process
output.collect(key, new Text(value)); //exception occurs at this line
}
}
System.out.println("Starting v14 ");
JobConf conf = new JobConf(RouteBuilderJob.class);
conf.setJobName("xyz");
String jarLocation =ClassUtil.findContainingJar(getClass());
System.out.println("path of jar file = " + jarLocation);
conf.setJarByClass(RouteBuilderJob.class);
conf.setMapOutputKeyClass(Text.class);
conf.setMapOutputValueClass(Info.class);
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(Text.class);
//am i missing something here???
conf.setMapperClass(RouteBuilderJob.RouteMapper.class);
conf.setCombinerClass(RouteBuilderJob.RouteReducer.class);
conf.setReducerClass(RouteBuilderJob.RouteReducer.class);
conf.setInputFormat(TextInputFormat.class);
conf.setOutputFormat(TextOutputFormat.class);
FileInputFormat.setInputPaths(conf, new Path(args[0]));
FileOutputFormat.setOutputPath(conf, new Path(args[1]));
JobClient.runJob(conf);
我遇到异常:
Error: java.io.IOException: wrong value class: class org.apache.hadoop.io.Text is not class com.xyz.mypackage.Info
at org.apache.hadoop.mapred.IFile$Writer.append(IFile.java:199)
at org.apache.hadoop.mapred.Task$CombineOutputCollector.collect(Task.java:1307)
at com.xyz.mypackage.job.MyJob$RouteReducer.reduce(MyJob.java:156)
at com.xyz.mypackage.job.MyJob$RouteReducer.reduce(MyJob.java:1)
内部信息对象(实现Writable
)使用Text
序列化
@Override
public void write(DataOutput out) throws IOException {
Gson gson = new Gson();
String searlizedStr = gson.toJson(this);
Text.writeString(out, searlizedStr);
}
@Override
public void readFields(DataInput in) throws IOException {
String s = Text.readString(in);
Gson gson = new Gson();
JsonReader jsonReader = new JsonReader(new StringReader(s));
jsonReader.setLenient(true);
Info info = gson.fromJson(jsonReader, Info.class);
//set fields using this.somefield = info.getsomefield()
}
最佳答案
从技术上讲,reduce 的输出类型应该与输入类型相同。如果您使用组合器,则必须如此,因为组合器的输出被馈送到您的 reducer 中。
关于java - 错误 : java. io.IOException : wrong value class: class org. apache.hadoop.io.Text 不是类 Myclass,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/21377011/