0.20.2 API hadoop version with java 5
I have started a maven project trying to implement the MapReduce algorithm in java 1.5.0_14. I have chosen the 0.20.2 API hadoop version. In the pom.xml i'm using thus the following dependency:
< dependency>
< groupId>org.apache.hadoop< /groupId>
< artifactId>hadoop-core< /artifactId>
< version>0.20.2< /version>
< /dependency>
But when I'm using an import to the org.apache.hadoop classes, I get the following error:
bad class file: ${HOME_DIR}\repository\org\apache\had开发者_如何学运维oop\hadoop-core\0.20.2\hadoop-core-0.20.2.jar(org/apache/hadoop/fs/Path.class) class file has wrong version 50.0, should be 49.0.
Does someone know how can I solve this issue.
Thanks.
Maven by default compiles to JDK 1.4 compatibility. You need to change this.
You need to add this to your pom.xml:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.0.2</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
[Edit: thank you Sean for pointing out Hadoop requires JDK 6]
I ran into this exact same problem. Turned out sbt itself was running on Java 5, which is the default on my Mac for a silly but valid reason. Once I changed my sbt script to explicitly start with Java6, everything worked fine.
Regardless of your maven-compiler-plugin's source & target configurations (that only controls how your own source code is compiled) you must use a 1.6 JVM to run Hadoop's code since it is compiled targetting "1.6" JVM.
So, just install a 1.6 java runtime and use that to run your program.
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