load external file from command prompt instead of using from classpath

Question

I am working with maven project and I have a quartz.properties file in /src/main/resources folder.

Now I can use this property file in two ways from this class as shown below:

/**
 * Create a StdSchedulerFactory that has been initialized via
 * <code>{@link #initialize(Properties)}</code>.
 *
 * @see #initialize(Properties)
 */
public StdSchedulerFactory(Properties props) throws SchedulerException {
    initialize(props);
}

/**
 * Create a StdSchedulerFactory that has been initialized via
 * <code>{@link #initialize(String)}</code>.
 *
 * @see #initialize(String)
 */
public StdSchedulerFactory(String fileName) throws SchedulerException {
    initialize(fileName);
}

Now I have made an executable jar using maven-shade-plugin and I am running in my ubuntu box as java -jar abc.jar and it works fine. It uses quartz.properties file from classpath automatically.

public static void main(String[] args) {
    StdSchedulerFactory factory = new StdSchedulerFactory();
    try {
        factory.initialize(App.class.getClassLoader().getResourceAsStream("quartz.properties"));
        Scheduler scheduler = factory.getScheduler();
        scheduler.start();
    } catch (SchedulerException ex) {
        System.out.println("error= " + ex);
    }
}

Now I am trying to make this program more generic by passing quartz.properties file from the command prompt while running my above jar file as shown below:

java -jar abc.jar quartz.properties

If I do like above, then it should use quartz.properties file what I am passing and not from classpath but if there is no argument passed then it should use default quartz.properties file. What is the best way to achieve this?

Answer 1

You have access to the command-line args in main :

if(args.length > 0) {
   ...
   factory.initialize(args[0]);
} else {
   ...
   factory.initialize(App.class.getClassLoader().getResourceAsStream("quartz.properties"));
}

If there is no initialize method that takes a String , then you can constructor a FileInputStream from the argument:

factory.initialize(new FileInputStream(new File(args[0])));

Answer 2

Check the API .

props.load( new FileInputStream("quartz.properties") );

PS. use try-with-resources so you don't leak the stream like I do, above, and add error handling