Hadoop is attempting to cast a Date object to WritableComparable, which Date does not implement, and is causing that exception.
Your keys must implement WritableComparable and your values must implement Comparable. On Wed, Oct 6, 2010 at 8:02 PM, Johannes.Lichtenberger <johannes.lichtenber...@uni-konstanz.de> wrote: > Hello, > > I'm getting a ClassCastException, when running my application: > > 10/10/07 04:31:10 WARN mapred.LocalJobRunner: job_local_0001 > java.lang.ClassCastException: class java.util.Date > at java.lang.Class.asSubclass(Class.java:3018) > at > org.apache.hadoop.mapred.JobConf.getOutputKeyComparator(JobConf.java:617) > at > org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:791) > at > org.apache.hadoop.mapred.MapTask$NewOutputCollector.<init>(MapTask.java:524) > at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:613) > at org.apache.hadoop.mapred.MapTask.run(MapTask.java:305) > at > org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:177) > > My key is a date (java.util.Date.class). > > final Job job = new Job(getConf()); > ... > job.setOutputKeyClass(java.util.Date.class); > job.setOutputValueClass(java.util.List.class); > > What's wrong? > > regards, > Johannes >
