setter 上的 @Autowired 与 @Required

在Spring框架中，我们经常会遇到需要自动装配依赖注入的情况。为了简化这个过程，Spring提供了两个注解：@Autowired和@Required。本文将介绍这两个注解的使用，并通过案例代码加以说明。

@Service
public class UserService {
    private UserRepository userRepository;
    @Autowired
    public void setUserRepository(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
    // ...
}

public class DatabaseConfig {
    private String url;
    private String username;
    private String password;
    @Required
    public void setUrl(String url) {
        this.url = url;
    }
    @Required
    public void setUsername(String username) {
        this.username = username;
    }
    @Required
    public void setPassword(String password) {
        this.password = password;
    }
    // ...
}