java - Dealing with command line arguments and Spring

Question

When I'm writing a Spring command line application which parses command line arguments, how do I pass them to Spring? Would I want to have my main() structured so that it first parses the command line args and then inits Spring? Even so, how would it pass the object holding the parsed args to Spring?

Answer 1

Two possibilities I can think of.

1) Set a static reference. (A static variable, although typically frowned upon, is OK in this case, because there can only be 1 command line invocation).

public class MyApp {
  public static String[] ARGS; 
  public static void main(String[] args) {
    ARGS = args;
      // create context
  }
}

You can then reference the command line arguments in Spring via:

<util:constant static-field="MyApp.ARGS"/>

Alternatively (if you are completely opposed to static variables), you can:

2) Programmatically add the args to the application context:

 public class MyApp2 {
   public static void main(String[] args) {
     DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();

        // Define a bean and register it
     BeanDefinition beanDefinition = BeanDefinitionBuilder.
       rootBeanDefinition(Arrays.class, "asList")
       .addConstructorArgValue(args).getBeanDefinition();
     beanFactory.registerBeanDefinition("args", beanDefinition);
     GenericApplicationContext cmdArgCxt = new GenericApplicationContext(beanFactory);
     // Must call refresh to initialize context 
     cmdArgCxt.refresh();

     // Create application context, passing command line context as parent
     ApplicationContext mainContext = new ClassPathXmlApplicationContext(CONFIG_LOCATIONS, cmdArgCxt);

     // See if it's in the context
     System.out.println("Args: " + mainContext.getBean("args"));
   }

   private static String[] CONFIG_LOCATIONS = new String[] {
     "applicationContext.xml"
   };

 }

Parsing the command line arguments is left as an exercise to the reader.