Question

I have an Interface with Component annotation and some classes that implemented it as follows:

@Component
public interface A {
}

public class B implements A {
}
public class C implements A {
}

Also, I have a class with an Autowired variable like this:

public class Collector {
    @Autowired
    private Collection<A> objects;

    public Collection<A> getObjects() {
        return objects;
    }
}

My context file consists of these definitions:

<context:component-scan base-package="org.iust.ce.me"></context:component-scan>

<bean id="objectCollector" class="org.iust.ce.me.Collector" autowire="byType"/>

<bean id="b" class="org.iust.ce.me.B"></bean>
<bean id="c" class="org.iust.ce.me.C"></bean>

And in the main class, I have some codes as follows:

ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
B b = (B) context.getBean("b");
C c = (C) context.getBean("c");
Collector objectCollector = (Collector) context.getBean("objectCollector");

for (A object : objectCollector.getObjects()) {
    System.out.println(object);
}

Output:

org.iust.ce.me.B@1142196
org.iust.ce.me.C@a9255c

---

These codes work well, but for some reasons I’m not willing to use xml context file. Besides it, I prefer to create the objects with the new operator rather than using the getBean() method. Nevertheless, since the AutoWiring is really good idea in programming, I don’t want to lose it.

Now I have two questions!!

1. how can I AutoWire classes that implements the A Interface without using the xml context file?
   Is it possible at all?

2. when I change the scope of a bean from singlton to
   prototype as follows:

   <bean id="b" class="org.iust.ce.me.B" scope="prototype"></bean>

   and instantiate several beans of it, only the bean which was instantiated during creating context, is injected into AutoWired variable. Why?

Any help will be appreciated.

Answer 1

Not sure the version of Spring you are using. But currently you can use @Configuration to replace .xml. Take a look at @Configuration

Below is the code in documentation

@Configuration
public class ServiceConfig {
    private @Autowired RepositoryConfig repositoryConfig;
    public @Bean TransferService transferService() {
        return new TransferServiceImpl(repositoryConfig.accountRepository());
    }
}

@Configuration
public interface RepositoryConfig {
    @Bean AccountRepository accountRepository();
}

@Configuration
public class DefaultRepositoryConfig implements RepositoryConfig {
    public @Bean AccountRepository accountRepository() {
        return new JdbcAccountRepository(...);
    }
}

@Configuration
@Import({ServiceConfig.class, DefaultRepositoryConfig.class}) // import the concrete config!
public class SystemTestConfig {
    public @Bean DataSource dataSource() { /* return DataSource */ }
}
public static void main(String[] args) {
    ApplicationContext ctx = new AnnotationConfigApplicationContext(SystemTestConfig.class);
    TransferService transferService = ctx.getBean(TransferService.class);
    transferService.transfer(100.00, "A123", "C456");
}