Cloudera Docs

Creating the UDF class

You define the UDF logic in a new class that returns the data type of a selected column in a table.

  1. In IntelliJ, click the vertical project tab, and expand hiveudf: hiveudf > src > main. Select the java directory, and on the context menu, select New > Java Class, and name the class, for example, TypeOf.
  2. Extend the GenericUDF class to include the logic that identifies the data type of a column.
    For example: 
    package com.mycompany.hiveudf;

import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDF;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.\
PrimitiveObjectInspectorFactory;
import org.apache.hadoop.io.Text;

public class TypeOf extends GenericUDF {
  private final Text output = new Text();

@Override
  public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentException {
    checkArgsSize(arguments, 1, 1);
    checkArgPrimitive(arguments, 0);
    ObjectInspector outputOI = PrimitiveObjectInspectorFactory.writableStringObjectInspector;
    return outputOI;
  }

@Override
  public Object evaluate(DeferredObject[] arguments) throws HiveException {
    Object obj;
    if ((obj = arguments[0].get()) == null) {
      String res = "Type: NULL";
      output.set(res);
      } else {
      String res = "Type: " + obj.getClass().getName();
      output.set(res);
    }
    return output;
  }

@Override
  public String getDisplayString(String[] children) {
    return getStandardDisplayString("TYPEOF", children, ",");
  }
}