Hive GUDF 自定义解压缩函数测试用例失败并出现错误“B 无法转换为 org.apache.hadoop.io.BytesWritable”

编程问答 2022-05-28

问题描述

我正在为通用 UDF 自定义解压缩评估函数编写测试用例，该函数可以解压缩 zip 文件。这个 jar 用于 Hivequery。 这里是测试用例的代码，

public void testEvaluate() throws HiveException,IOException {
    Unzip unzip = new Unzip();
    File resourcesDirectory = new File("src/test/resources/test.zip");
    byte[] bytes = Files.readAllBytes( resourcesDirectory.toPath() );

    ObjectInspector binaryOI = PrimitiveObjectInspectorFactory.writableBinaryObjectInspector;
    ObjectInspector[] arguments = {binaryOI};
    unzip.initialize(arguments);

    GenericUDF.Deferredobject valueObj0 = new GenericUDF.DeferredJavaObject(bytes);
    GenericUDF.Deferredobject[] args = { valueObj0 };

    unzip.evaluate(args  );}

我收到如下错误,

java.lang.classCastException: [B cannot be cast to org.apache.hadoop.io.BytesWritable

at org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableBinaryObjectInspector.getPrimitiveJavaObject(WritableBinaryObjectInspector.java:49)
at Unzip.evaluate(Unzip.java:32)
at UnzipTest.testEvaluate(UnzipTest.java:96)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
at org.junit.runners.BlockJUnit4ClassRunner.runchild(BlockJUnit4ClassRunner.java:103)
at org.junit.runners.BlockJUnit4ClassRunner.runchild(BlockJUnit4ClassRunner.java:63)
at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
at org.junit.runners.ParentRunner.runchildren(ParentRunner.java:329)
at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

从 Deferredobject[] args 读取字节时，在 line 处发生错误，

 -  byte[] input = elementOI.getPrimitiveJavaObject( arg[0].get() );

PS：test.zip 包含一个压缩到 test.zip 的文本文件（带有测试字符串）

解决方法

您需要使用 Hive 可以使用的 Writable 来包装 byte[]，在您的情况下为 BytesWritable。
如您所见WritableBinaryObjectInspector.getPrimitiveJavaObject expects BytesWritable object as an input,not an array of bytes.

尝试代替

GenericUDF.DeferredObject valueObj0 = new GenericUDF.DeferredJavaObject(bytes);

执行以下操作：

GenericUDF.DeferredObject valueObj0 = new GenericUDF.DeferredJavaObject(new BytesWritable(bytes));

在本地重现您的案例，我能够在 UDF byte[] 方法中成功检索 evaluate。

hivehiveqljavajava