Using a bean via dependency injection with @Autowired

Spring configuration beans, such as the one in the Defining a bean explicitly with @Bean recipe are automatically discovered and used by Spring. To use a bean (any kind of bean) in one of your classes, add the bean as a field and annotate it with @Autowired. Spring will automatically initialize the field with the bean. In this recipe, we'll use an existing bean in a controller class.

Getting ready

We will use the code from the Defining a bean implicitly with @Component recipe, where we defined a UserService bean.

How to do it…

Here are the steps to use an existing bean in one of your classes:

1. In the controller class, add a UserService field annotated with @Autowired:

   @Autowired
   UserService userService;

2. In a controller method, use the UserService field:

   @RequestMapping("hi")
   @ResponseBody
   public String hi() {
     return "nb of users: " + userService.findNumberOfUsers();
   }

3. In a web browser, go to http://localhost:8080...