我正在为Hive编写通用自定义项。当我添加jar并试图创建一个指向类的临时函数时，我得到了一个错误，因此函数创建没有成功。有人能为genericudf函数提供java代码模板吗？该函数接受一个string类型的参数并返回map类型的对象。关于对象检查器类有太多的混淆，所以如果有人为这个函数的输入类型和返回类型提供非常基本的模板的话，将会有很大的帮助。
所以我的java代码是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;

    }

}

这就是当我试图在Hive中创建函数来对抗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