Most J2EE developers have at least heard of the Spring framework and know that it is an excellent framework for creating enterprise applications. I have recently needed to create an application that runs from the command line and is short lived. It has no GUI but I wanted it to be configurable and extendable in various ways. To that end, I defined a bunch of interfaces for the objects in the system to use when interfacing with other objects. Then I started thinking about the implementations of these interfaces and the factory classes I would need to create. I said to myself “Self, doesn’t Spring already do this?” and I answered myself, “Why, yes”. So I decided to try it.
The result is an extremly configurable application to which I can add or remove functionality with some minor configuration changes. I defined a bean that constituted the root object of the system. Here it is:
package com.dhptech.spring.poja;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
* The main class for this application. It is responsible for parsing the
* command line and controlling the action.
*
* @author danap
*/
public abstract class SpringMain {
public static final String NAME = "main";
public static final String CONFIG_XML = "spring.xml";
/**
* process the arguments and execute the command.
*
* @param args the arguments.
*/
public abstract int process(String[] args);
/**
* The main function for this application. Sets up the spring context
* and dispatces the the main data distributor class.
*
* @param args the command line arguments.
*
* @return 0 if no errors occurr.
*/
public static int main(String[] args) {
try {
ApplicationContext ctx = new ClassPathXmlApplicationContext(CONFIG_XML);
main main = (Main) ctx.getBean(NAME);
return main.process(args);
} catch( Throwable t ) {
t.printStackTrace();
return -1;
}
}
}Create the spring.xml file with a bean named “main” that extends com.dhptech.spring.poja.Main. Pretty darn simple, huh?