我的mapreduce作业在eclipse中组装时运行正常，所有可能的hadoop和HiveJAR都作为依赖项包含在eclipse项目中(这些是单节点本地hadoop安装附带的jar。
然而，当尝试运行使用maven项目（见下文）组装的相同程序时，我得到：
Exception in thread "main" java.lang.IncompatibleClassChangeError: Found interface org.apache.hadoop.mapreduce.JobContext, but class was expected使用以下maven项目组装程序时会发生此异常：
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.bigdata.hadoop</groupId>
<artifactId>FieldCounts</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>FieldCounts</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-hdfs</artifactId>
<version>2.2.0</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>2.2.0</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-mapreduce-client-jobclient</artifactId>
<version>2.2.0</version>
</dependency>
<dependency>
<groupId>org.apache.hive.hcatalog</groupId>
<artifactId>hcatalog-core</artifactId>
<version>0.12.0</version>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>16.0.1</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>${jdk.version}</source>
<target>${jdk.version}</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>attached</goal>
</goals>
<phase>package</phase>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<archive>
<manifest>
<mainClass>com.bigdata.hadoop.FieldCounts</mainClass>
</manifest>
</archive>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>- 请告知在何处以及如何找到兼容的hadoop jar*
[更新\1]我正在运行hadoop 2.2.0.2.0.6.0-101
我在这里发现：https://github.com/kevinweil/elephant-bird/issues/247
hadoop1.0.3:jobcontext是一个类
hadoop2.0.0:jobcontext是一个接口
在pom.xml中，我有三个版本为2.2.0的jar
hadoop-hdfs 2.2.0
hadoop-common 2.2.0
hadoop-mapreduce-client-jobclient 2.2.0
hcatalog-core 0.12.0唯一的例外是 hcatalog-core 哪个版本是0.12.0，我找不到这个jar的最新版本，我需要它！
我怎样才能找到这4个jar里的哪一个 java.lang.IncompatibleClassChangeError: Found interface org.apache.hadoop.mapreduce.JobContext, but class was expected ?
请告诉我怎么解决这个问题(我看到的唯一解决方案是从源代码处编译所有内容！）
[/更新\u 1]
我婚后工作的全文：
package com.bigdata.hadoop;
import java.io.IOException;
import java.util.*;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.util.*;
import org.apache.hcatalog.mapreduce.*;
import org.apache.hcatalog.data.*;
import org.apache.hcatalog.data.schema.*;
import org.apache.log4j.Logger;
public class FieldCounts extends Configured implements Tool {
public static class Map extends Mapper<WritableComparable, HCatRecord, TableFieldValueKey, IntWritable> {
static Logger logger = Logger.getLogger("com.foo.Bar");
static boolean firstMapRun = true;
static List<String> fieldNameList = new LinkedList<String>();
/**
* Return a list of field names not containing `id` field name
* @param schema
* @return
*/
static List<String> getFieldNames(HCatSchema schema) {
// Filter out `id` name just once
if (firstMapRun) {
firstMapRun = false;
List<String> fieldNames = schema.getFieldNames();
for (String fieldName : fieldNames) {
if (!fieldName.equals("id")) {
fieldNameList.add(fieldName);
}
}
} // if (firstMapRun)
return fieldNameList;
}
@Override
protected void map( WritableComparable key,
HCatRecord hcatRecord,
//org.apache.hadoop.mapreduce.Mapper
//<WritableComparable, HCatRecord, Text, IntWritable>.Context context)
Context context)
throws IOException, InterruptedException {
HCatSchema schema = HCatBaseInputFormat.getTableSchema(context.getConfiguration());
//String schemaTypeStr = schema.getSchemaAsTypeString();
//logger.info("********schemaTypeStr**********: "+schemaTypeStr);
//List<String> fieldNames = schema.getFieldNames();
List<String> fieldNames = getFieldNames(schema);
for (String fieldName : fieldNames) {
Object value = hcatRecord.get(fieldName, schema);
String fieldValue = null;
if (null == value) {
fieldValue = "<NULL>";
} else {
fieldValue = value.toString();
}
//String fieldNameValue = fieldName+"."+fieldValue;
//context.write(new Text(fieldNameValue), new IntWritable(1));
TableFieldValueKey fieldKey = new TableFieldValueKey();
fieldKey.fieldName = fieldName;
fieldKey.fieldValue = fieldValue;
context.write(fieldKey, new IntWritable(1));
}
}
}
public static class Reduce extends Reducer<TableFieldValueKey, IntWritable,
WritableComparable, HCatRecord> {
protected void reduce( TableFieldValueKey key,
java.lang.Iterable<IntWritable> values,
Context context)
//org.apache.hadoop.mapreduce.Reducer<Text, IntWritable,
//WritableComparable, HCatRecord>.Context context)
throws IOException, InterruptedException {
Iterator<IntWritable> iter = values.iterator();
int sum = 0;
// Sum up occurrences of the given key
while (iter.hasNext()) {
IntWritable iw = iter.next();
sum = sum + iw.get();
}
HCatRecord record = new DefaultHCatRecord(3);
record.set(0, key.fieldName);
record.set(1, key.fieldValue);
record.set(2, sum);
context.write(null, record);
}
}
public int run(String[] args) throws Exception {
Configuration conf = getConf();
args = new GenericOptionsParser(conf, args).getRemainingArgs();
// To fix Hadoop "META-INFO" (http://stackoverflow.com/questions/17265002/hadoop-no-filesystem-for-scheme-file)
conf.set("fs.hdfs.impl",
org.apache.hadoop.hdfs.DistributedFileSystem.class.getName());
conf.set("fs.file.impl",
org.apache.hadoop.fs.LocalFileSystem.class.getName());
// Get the input and output table names as arguments
String inputTableName = args[0];
String outputTableName = args[1];
// Assume the default database
String dbName = null;
Job job = new Job(conf, "FieldCounts");
HCatInputFormat.setInput(job,
InputJobInfo.create(dbName, inputTableName, null));
job.setJarByClass(FieldCounts.class);
job.setMapperClass(Map.class);
job.setReducerClass(Reduce.class);
// An HCatalog record as input
job.setInputFormatClass(HCatInputFormat.class);
// Mapper emits TableFieldValueKey as key and an integer as value
job.setMapOutputKeyClass(TableFieldValueKey.class);
job.setMapOutputValueClass(IntWritable.class);
// Ignore the key for the reducer output; emitting an HCatalog record as
// value
job.setOutputKeyClass(WritableComparable.class);
job.setOutputValueClass(DefaultHCatRecord.class);
job.setOutputFormatClass(HCatOutputFormat.class);
HCatOutputFormat.setOutput(job,
OutputJobInfo.create(dbName, outputTableName, null));
HCatSchema s = HCatOutputFormat.getTableSchema(job);
System.err.println("INFO: output schema explicitly set for writing:"
+ s);
HCatOutputFormat.setSchema(job, s);
return (job.waitForCompletion(true) ? 0 : 1);
}
public static void main(String[] args) throws Exception {
String classpath = System.getProperty("java.class.path");
//System.out.println("***CLASSPATH: "+classpath);
int exitCode = ToolRunner.run(new FieldCounts(), args);
System.exit(exitCode);
}
}和复杂键的类：
package com.bigdata.hadoop;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.io.WritableComparable;
import com.google.common.collect.ComparisonChain;
public class TableFieldValueKey implements WritableComparable<TableFieldValueKey> {
public String fieldName;
public String fieldValue;
public TableFieldValueKey() {} //must have a default constructor
//
public void readFields(DataInput in) throws IOException {
fieldName = in.readUTF();
fieldValue = in.readUTF();
}
public void write(DataOutput out) throws IOException {
out.writeUTF(fieldName);
out.writeUTF(fieldValue);
}
public int compareTo(TableFieldValueKey o) {
return ComparisonChain.start().compare(fieldName, o.fieldName)
.compare(fieldValue, o.fieldValue).result();
}
}
5条答案
按热度按时间uqzxnwby1#
您需要重新编译“hcatalog core”以支持hadoop2.0.0。目前“hcatalog core”只支持hadoop1.0
ggazkfy82#
hadoop经历了从
Hadoop 1.0至Hadoop 2.0. 一个副作用是针对hadoop1.0编译的代码与hadoop2.0不兼容，反之亦然。然而，源代码大部分是兼容的，因此只需要用目标hadoop发行版重新编译代码。“例外”
Found interface X, but class was expected“在hadoop2.0上运行为hadoop1.0编译的代码时非常常见，反之亦然。您可以找到集群中使用的正确hadoop版本，然后在pom.xml文件中指定hadoop版本使用集群中使用的相同版本的hadoop构建项目并部署它。
jv4diomz3#
查找这样的条目
在pom.xml中。它们定义了要使用的hadoop版本。根据您的要求进行更改或删除。
vaqhlq814#
就连我也遇到了这个问题。正在尝试将hcatmultipleinputs与hive-hcatalog-core-0.13.0.jar一起使用。我们使用的是hadoop2.5.1。
以下代码更改帮助我解决了此问题：
d8tt03nd5#
显然，hadoop和hive版本之间存在版本不兼容。您需要升级（或降级）hadoop版本或hive版本。
这是由于hadoop1和hadoop2之间的不兼容性造成的。