Create the UDF class
You define the UDF logic in a new class that returns the data type of a selected column in a table.
- 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.
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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, ","); } }