Spring IOC without xml

Since Java adopted annotations, most of application has started using it to cut down the xml configuration, spring 3 also introduce the annotation driven configuration, let’s explore.

Here is the Martin Fowler’s famous dependency injection example of moviLister and moveFinder

MovieFinder

public interface MovieFinder {

    List findAll();

}

Implementation of MovieFinder

public class ColonMovieFinder implements MovieFinder {

            Resource filename;

           

            public Resource getFilename() {

                        return filename;

            }

           

            public void setFilename(Resource filename) {

                        this.filename = filename;

            }

            @Override

            public List<Movie> findAll() {

                        List<Movie> movies=null;

                        try {

                                    movies = inputStreamAsString(this.filename.getInputStream());

                        } catch (IOException e) {

                                    // TODO Auto-generated catch block

                                    e.printStackTrace();

                        }

                        return movies;

            }

           

}      

MovieLister needs MovieFinder dependency

public class MovieLister {

            private MovieFinder finder;

            public void setFinder(MovieFinder finder) {

                        this.finder = finder;

            }

           

           

            public Movie[] moviesDirectedBy(String arg) {

                        List allMovies = finder.findAll();

                        for (Iterator it = allMovies.iterator(); it.hasNext();) {

                                    Movie movie = (Movie) it.next();

                                    if (!movie.getDirector().equals(arg))

                                                it.remove();

                        }

                        return (Movie[]) allMovies.toArray(new Movie[allMovies.size()]);

            }

           

           

}

Setup the dependency

1.       Configuration java class need to be written to define the dependency.

2.       Add @Configuration to tell the spring about your configuration class

3.       @Bean should be define to tell the spring, they are spring bean

4.       initMethod and distroyMethod attribute should be used in @Bean annotation to define the life cycle.

5.       @Scope should be used to define the scope is singleton or prototype or request ect

@Configuration

public class AppConfig {

            public

            @Bean(destroyMethod="distroy",initMethod="init")

             @Scope("prototype")

            MovieLister movieLister() {

                        MovieLister moviLister = new MovieLister();

                        moviLister.setFinder(movieFinder());

                        return moviLister;

            }

            public @Bean

            MovieFinder movieFinder() {

                        ColonMovieFinder colonMovieFinder = new ColonMovieFinder();

                        Resource resource = new ClassPathResource("examples/movies.txt");

                        colonMovieFinder.setFilename(resource);

                        return colonMovieFinder;

            }

}

Construct the application context

1.       Pass the class having @Configuration to AnnotationConfigApplicationContext constructor

2.       More than one configuration can be written and all of them can be passed to constructor as it support java 5 vargar

AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

Test class

public class ApplicationContextAnnotationTest {

            public static void main(String[] args) {

        //Initialize IoC Container

                        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

                        //Retrieve the bean from Container

                        MovieLister myBean = context.getBean(MovieLister.class);

                        for(Movie m : myBean.moviesDirectedBy("Rajnikant")){

                                    System.out.println(m); 

                        }

                        context.destroy();

                        context.close();

            }

           

}

Problems what if you two bean of same type?

1.       Pass the name to @bean attribute

2.       Get the bean from context using been class and name.

Register bean by name

            public @Bean(name="moviFinder")

            MovieFinder movieFinder() {

                        ColonMovieFinder colonMovieFinder = new ColonMovieFinder();

                        Resource resource = new ClassPathResource("examples/movies.txt");

                        colonMovieFinder.setFilename(resource);

                        return colonMovieFinder;

            }

Retrieve bean by name

            AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

           

MovieFinder myFind = context.getBean("moviFinder",MovieFinder.class);

Problem : this approach doesn’t cut the configuration it just move the configuration from xml file to java file, right way to cut the configuration is autowiring that I will post in next blog