当我试图用maven（或者用ide intellij）编译pig udf时，出现以下错误：

cannot access org.apache.hadoop.io.WritableComparable
class file for org.apache.hadoop.io.WritableComparable not found

所以我想我应该在pom文件中添加一个对hadoop内核的依赖，但是仍然没有任何改变，尽管我检查了，writeablecomparable类在jar中。
我的自定义项类如下所示：

public class INCREMENTAL_UPDATE extends EvalFunc<DataBag> {

    TupleFactory tupleFactory = TupleFactory.getInstance();
    BagFactory bagFactory = BagFactory.getInstance();

    public DataBag exec(Tuple input) throws IOException {
        if (null == input || input.size() != 0) {
            return null;
        }

        try {
            DataBag inputbag = (DataBag) input.get(0);
            Iterator it = inputbag.iterator();

            DataBag outputbag = bagFactory.newDefaultBag();

            Tuple previousTuple = null;
            while (it.hasNext()) {
                Tuple currentTuple = (Tuple) it.next();
                Tuple outputTuple = tupleFactory.newTuple();

                for (int i = 0; i < currentTuple.size(); i++) {
                    Object currentvalue = currentTuple.get(i);
                    if (currentvalue == null) {
                        outputTuple.append(currentvalue);
                    } else {
                        outputTuple.append(previousTuple.get(i));
                    }
                }

                previousTuple = outputTuple;
                outputbag.add(outputTuple);
           }
            return outputbag;
        } catch (Exception e) {
           throw new IOException("UDF INCREMENTAL_UPDATE failed");
        }
    }
}

我还没有弄清楚这是否真的有效，因为我不确定是否分发了自定义项。如果是的话，以前的元组可能就不起作用了。但我甚至不能测试出来，因为我不能编译，因为上面的错误。