在Hadoop中，使用configuration的时候，首先自动加载了默认的配置文件，比如core-default.xml、core-default.xml资源文件，代码如下：
static{
//print deprecation warning if hadoop-site.xml is found in classpath
ClassLoader cL = Thread.currentThread().getContextClassLoader();
if (cL == null) {
cL = Configuration.class.getClassLoader();
}
if(cL.getResource("hadoop-site.xml")!=null) {
LOG.warn("DEPRECATED: hadoop-site.xml found in the classpath. " +
"Usage of hadoop-site.xml is deprecated. Instead use core-site.xml, "
+ "mapred-site.xml and hdfs-site.xml to override properties of " +
"core-default.xml, mapred-default.xml and hdfs-default.xml " +
"respectively");
}
addDefaultResource("core-default.xml");
addDefaultResource("core-site.xml");
}
建立一个良好的Hadoop框架，势必会用很多自己写的资源文件，hadoop对xml支持好于对properties文件的支持，hadoop中的配置文件几乎都是是用xml写成的。那么如何加载自有的xml资源文件，使其成为全局的Configuration呢？
hadoop jar ‘你的jar包’ 之后跟随着一个-conf的命令，加载自有资源，靠的就是这个命令，ok，不废话了，上代码：
package com.ecom.asillin.utils;
import org.apache.hadoop.conf.Configuration;
/**
* Created with IntelliJ IDEA.
* User: asilin
* Date: 14-10-23
* Time: 上午10:17
* To change this template use File | Settings | File Templates.
*/
public class ConfigurationUtils {
//静态类单例
private static class Singleton{
public static ConfigurationUtils instance = new ConfigurationUtils();
}
private ConfigurationUtils(){}
public static ConfigurationUtils getInstance(){
return Singleton.instance;
}
//添加资源
public static Configuration create(){
Configuration conn = new Configuration();
addSources(conn);
return conn;
}
//添加默认资源 -conf 之后的资源
private static Configuration addSources(Configuration conn){
conn.addResource("你的xml文件名称，带有.xml,不要忘记");
return conn;
}
}
ok 现在完整的运行命令就是： hadoop jar ‘a.jar’ -conf ‘yourself.xml’
Ubuntu 13.04上搭建Hadoop环境