Hadoop配置属性返回Null

Question

我写了一个简单的代码来测试如何在Hadoop中设置配置。

public static void main(String[] args) { 

     Configuration conf = new Configuration(); 
     conf.addResource("~/conf.xml"); 
     System.out.println(conf); 
     System.out.println(conf.get("color")); 
} 

上述程序的输出是：

Configuration: core-default.xml, core-site.xml, ~/conf.xml 
null 

因此conf.get("color")返回null。不过，我已经明确地设置该属性在conf.xml如下：

<property> 
     <name>color</name> 
     <value>yellow</value> 
     <description>Color</description> 
</property> 

Answer 1

资源需要添加一个网址，否则字符串被解释为一个类路径资源（这在目前不能解决，将被忽略 - 我知道你，你认为一个警告消息将被倾倒的地方）：

/** 
* Add a configuration resource. 
* 
* The properties of this resource will override properties of previously 
* added resources, unless they were marked <a href="#Final">final</a>. 
* 
* @param name resource to be added, the classpath is examined for a file 
*    with that name. 
*/ 
public void addResource(String name) { 
    addResourceObject(name); 
} 

不管怎样，试试这个（我得到的SYSERR黄色）：

@Test 
public void testConf() throws MalformedURLException { 
    Configuration conf = new Configuration(); 

    conf.addResource(new File("~/conf.xml") 
      .getAbsoluteFile().toURI().toURL()); 
    conf.reloadConfiguration(); 
    System.err.println(conf); 

    System.err.println(conf.get("color")); 
}