我正在使用已經安裝了hadoop並被其他用戶嚴重使用和測試的RHEL Intel羣集。我試圖學習使用該框架,所以我從這裏開始教程:http://hadoop.apache.org/docs/r0.17.0/mapred_tutorial.html使用Hadoop helloworld和非泛型Iterator的Java版本配置
所以,我將WordCount.java的源代碼從上面的鏈接複製到〜/ hadooptest /中,然後按照編譯時會稍微修改一下版本錯誤,這裏是編譯嘗試的輸出以及一些相關的系統信息。
[[email protected] hadooptest]$ pwd
/home/X/hadooptest
[[email protected] hadooptest]$ javac -version
Eclipse Java Compiler v_677_R32x, 3.2.1 release, Copyright IBM Corp 2000, 2006. All rights reserved.
[[email protected] hadooptest]$ $JAVA_HOME/bin/java -version
java version "1.6.0_24"
Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02, mixed mode)
[[email protected] hadooptest]$ hadoop version
Hadoop 0.20.2-cdh3u5
Subversion file:///data/1/tmp/topdir/BUILD/hadoop-0.20.2-cdh3u5 -r 30233064aaf5f2492bc687d61d72956876102109
Compiled by root on Fri Oct 5 18:45:42 PDT 2012
From source with checksum de1770d69aa93107a133657faa8ef467
[[email protected] hadooptest]$ javac -source 5.0 -classpath /usr/lib/hadoop-1.0.1/hadoop-core-1.0.1.jar -d wordcount_classes/ WordCount.java
----------
1. ERROR in WordCount.java (at line 0)
package org.myorg;
^
The type Iterator is not generic; it cannot be parameterized with arguments <V2>
----------
2. ERROR in WordCount.java (at line 29)
public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {
^^^^^^^^
The type Iterator is not generic; it cannot be parameterized with arguments <IntWritable>
----------
2 problems (2 errors)[[email protected] hadooptest]$
我知道這個問題可能並不是Hadoop特有的,但我主要不是Java用戶。當我習慣使用Hadoop的母語進行操作時,我可能會選擇切換到使用C++庫(但這是另一天的故事)。我用Google搜索這個問題,我覺得這是典型的指示使用1.4.X JRE ......,我們也做的有:
[[email protected] hadooptest]$ java -version
java version "1.4.2"
gij (GNU libgcj) version 4.1.2 20080704 (Red Hat 4.1.2-48)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
[[email protected] hadooptest]$ $JAVA_HOME/bin/java -version
java version "1.6.0_24"
Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02, mixed mode)
我已經建立了在〜/ .bash_profile直接到1.6 JRE,但大概javac被配置爲仍然重定向到默認的1.4。我怎樣才能解決這個問題?
因此,您正在編譯Java5並在Java4 JVM上運行?爲什麼不從示例jar中獲取wordcount示例? –
@ThomasJungblut,當你說我正在運行一個Java4 JVM時,你是說基於'gij(GNU libgcj)版本4.1.2 20080704(Red Hat 4.1.2-48)'''的行嗎?當我真正運行它時,我將使用$ JAVA_HOME中定義的1.6 JRE。就這個例子而言,你指的是什麼罐子? Mine與我鏈接到的網站上發佈的源代碼完全相同。 –