Wiring components in Spring

After mock testing the components structure of my Spring Web application, I am ready to create a real Knight - Quest couple and see how to wire them together.

Firstly, I create a concrete Quest, SlayDragonQuest, and I let Spring know, through annotations, that it is a component and it is qualified as quest.

@Component
@Qualifier("quest")
public class SlayDragonQuest implements Quest {
    public String embark() {
        return "Embarking on quest to slay the dragon!";
    }
}

Then I modify my BraveKnight to let Spring know that it is a component too, named knight, and that it is autowired to the component that is qualified as quest.

@Component("knight")
public class BraveKnight implements Knight {
    // ...
    @Autowired
    public BraveKnight(@Qualifier("quest") Quest quest) {
        this.quest = quest;
    }
 // ...
}

Let's have a look to the KnightController.

@RestController // 1
public class KnightController {
    @Resource
    private Knight knight; // 2

    @RequestMapping("/quest")
    public String quest() { // 3
        return knight.doQuest();
    }
}

1. It is annotated as a RestController, so Spring would use it as a RESTful service.
2. Its knight field is annotated as resource, so Spring would try to inject in it a component named as its type (but starting with a lowercase letter), meaning, the BraveKnight.
3. Any request to the /quest URI is mapped to this method.

I only have to run it:

If something is not clear on this last step, you may get some hints from the previous Hello Spring Boot post.

I have written this code while reading the first chapter of Spring in Action, Fourth Edition by Craig Walls. It diverges a bit from the original version, since I have developed a Maven Spring Boot Web project, and here I have used annotations instead of the classic xml configuration to signal beans to Spring and wire them together.

Full code on github.