我正在尝试为Hive编写GenericUDF。当我添加JAR并尝试创建指向该类的临时函数时，我收到错误，因此函数创建不成功。有人可以为GenericUDF函数提供Java代码模板，该函数接受一个String类型的参数并返回一个Map类型的对象。关于Object Inspector类有很多混淆，所以如果有人为我提供了输入类型的非常基本的模板和这个函数的返回类型，那将会有很大的帮助。
所以我的Java代码在这里： -
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;
}
}
当我尝试在Hive中针对JAR创建函数时会发生这种情况： -
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