I am trying to write GenericUDF for Hive. When I add JAR and try to create a temporary function pointing to the class, I get an error, so function creation does not succeed. Can someone provide Java code template for GenericUDF function that accepts one argument of type String and returns an object of type Map. There is so much confusion regarding Object Inspector classes, so it will be of much help if someone provides me very basic template for input type and return type of this function.
So my Java code is here:-
package test;
import java.util.HashMap;
import java.util.Map;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
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.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.JavaIntObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorConverter;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.StringObjectInspector;
public class CustomUDF extends GenericUDF
{
Map<Character,Integer> myMap;
StringObjectInspector elementOI;
@Override
public String getDisplayString(String[] arg0)
{
// TODO Auto-generated method stub
return "myfunction()";
}
@Override
public ObjectInspector initialize(ObjectInspector[] arg) throws UDFArgumentException
{
if (arg.length != 1)
{
throw new UDFArgumentLengthException("myfunction() only takes 1 argument: String");
}
// 1. Check we received the right object types.
ObjectInspector a = arg[0];
if (!(a instanceof StringObjectInspector))
{
throw new UDFArgumentException("Argument must be a string");
}
// The custom function is going to return an object of type Map<Character,Integer>
myMap = new HashMap<Character,Integer>();
this.elementOI = (StringObjectInspector) a;
// I could not find way to create ObjectInspector for Character so I am creating ObjectInspector for String
return ObjectInspectorFactory.getStandardMapObjectInspector(PrimitiveObjectInspectorFactory.javaStringObjectInspector, PrimitiveObjectInspectorFactory.javaIntObjectInspector);
}
@Override
public Object evaluate(DeferredObject[] arg) throws HiveException
{
myMap.clear();
String str = elementOI.getPrimitiveJavaObject(arg[0].get());
// check for nulls
if (str == null)
{
return null;
}
for(Character ch: str.toCharArray())
{
myMap.put(ch,1);
}
return myMap;
}
}
And this is what happens when I try to create function in Hive against the JAR:-
hive> add jar test.jar;
Added [test.jar] to class path
Added resources: [test.jar]
hive> create temporary function myfunction as 'test.CustomUDF';
java.lang.UnsupportedClassVersionError: test/CustomUDF : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:803)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:278)
at org.apache.hadoop.hive.ql.exec.FunctionTask.getUdfClass(FunctionTask.java:307)
at org.apache.hadoop.hive.ql.exec.FunctionTask.createTemporaryFunction(FunctionTask.java:174)
at org.apache.hadoop.hive.ql.exec.FunctionTask.execute(FunctionTask.java:74)
at org.apache.hadoop.hive.ql.exec.Task.executeTask(Task.java:160)
at org.apache.hadoop.hive.ql.exec.TaskRunner.runSequential(TaskRunner.java:86)
at org.apache.hadoop.hive.ql.Driver.launchTask(Driver.java:1631)
at org.apache.hadoop.hive.ql.Driver.execute(Driver.java:1390)
at org.apache.hadoop.hive.ql.Driver.runInternal(Driver.java:1197)
at org.apache.hadoop.hive.ql.Driver.run(Driver.java:1024)
at org.apache.hadoop.hive.ql.Driver.run(Driver.java:1014)
at org.apache.hadoop.hive.cli.CliDriver.processLocalCmd(CliDriver.java:250)
at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:202)
at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:413)
at org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:786)
at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:680)
at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:619)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
FAILED: Execution Error, return code -101 from org.apache.hadoop.hive.ql.exec.FunctionTask. test/CustomUDF : Unsupported major.minor version 52.0
