Question

我编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"));
}

以上程序的输出是：

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

因此conf.get("color")会返回null。但是，我已在conf.xml中明确设置了该属性，如下所示：

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

Answer 1

需要将资源添加为URL，否则将String解释为类路径资源（此时不会解析并被忽略 - 我知道您认为警告消息会被转储到某处）：< / p>

/**
 * 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);
}

无论如何，试试这个（我在syserr中变黄）：

@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"));
}

Hadoop配置属性返回Null

1 个答案: