springMVC普通类中调用mapper或service接口

在封装的时候，发现普通类注入mapper都为null,在网上看到多种解决方案，写一遍记录一下。

@Component
public class MutualStepPage {
    private UserMapper userMapper;

    public static MutualStepPage mutualStepPage;

    @Autowired
    public MutualStepPage(UserMapper userMapper) {
        this.userMapper = userMapper;
    }

    @PostConstruct
    public void init() {
        mutualStepPage = this;
    }
    //可以正常使用
}
     mutualStepPage.userMapper.FindUserByToken(token);