...
public Class SingerWithInterface implements InitializingBean {
	private static final String DEFAULT_NAME = "Eric Clapton";

	private String name;
	private int age = Integer.MIN_VALUE;

	public void setName(String name) {
		this.name = name;
	}

	public void setAge(int age) {
		this.age = age;
	}

	/*
		init 메서드 대신 InitializingBean 인터페이스에 정의된 afterPropertiesSet 함수를
		구현한다.
	*/
	public void afterPropertiesSet() throw Exception {
		System.out.println("빈 초기화");

		if (name == null) {
			System.out.println("기본 가수 이름 설정");
			name = DEFAULT_NAME;
		}

		if (age == Integer.MIN_VALUE) {
			throw new IllegalArgumentException(
					SingerWithInterface.class +
					" 빈 타입에는 반드시 age 프로퍼티를 설정해야 합니다.");
		}
	}

	public String toString() {
		return "\t이름 : " + name + "\n\t나이 : " + age);
	}

	public static void main(String... args) {
		GenericXmlApplicationContext ctx = new GenericXmlApplicationContext();
		ctx.load("classpath:spring/app-context-xml.xml");
		ctx.refresh();

		getBean("singerOne", ctx);
		getBean("singerTwo", ctx);
		getBean("singerThree", ctx);

		ctx.close();
	}

	public static Singer getBean(Sting beanName, ApplicationContext ctx) {
		try {
			Singer bean = (Singer) ctx.getBean(beanName);
			System.out.println(bean);
			return bean;
		} catch(BeanCreationException ex) {
			System.out.println("빈 구성 도중 에러 발생: " + ex.getMessage());
			return null;
		}
	}
}