无法在Hadoop jar上加载application.properties（NullPointerException）

Question

I've looked at all kinds of answers for this problem. None of them work.

I have the following code:

import java.util.Properties;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.FileNotFoundException;
import java.io.IOException;

public class ApplicationConfig {

    private static Logger LOG;

    private String appConfigFileLocation = "application.properties"; 
    private Properties appConfig;

    private static ApplicationConfig instance;

    public static ApplicationConfig getInstance() {
        if(instance == null) {
            instance = new ApplicationConfig();
        }

        return instance;
    } 

    private ApplicationConfig() {
        LOG = LoggerFactory.getLogger(this.getClass().getSimpleName());

        appConfig = new Properties();

        try {
            LOG.info("Reading config from " + appConfigFileLocation);

            appConfig.load(ClassLoader.getSystemResourceAsStream(appConfigFileLocation));

            LOG.info("Done reading config from " + appConfigFileLocation);
        } catch (FileNotFoundException e) {
            LOG.error("Encountered FileNotFoundException while reading configuration: " + e.getMessage());
            throw new RuntimeException(e);
        } catch (IOException e) {
            LOG.error("Encountered IOException while reading configuration: " + e.getMessage());
            throw new RuntimeException(e);
        }
    }
}

I created a JAR file. The JAR file has application.properties at the root. I also copied the application.properties file in /etc/hadoop/conf and in the target/classes/ directory.

I use the hadoop jar command to execute the code.

But I keep getting the error: java.lang.NullPointerException at java.util.Properties$LineReader.readLine(Properties.java:434)

Please help me at resolving this frustrating error!

Answer 1

Found the error.

hadoop jar checks in the Hadoop classpath. Even though the file was there in the Hadoop classpath, it didn't have read permissions from the Hadoop user.

A simple sudo chmod a+r /etc/hadoop/conf/application.properties did the trick!