@Autowired注解和静态属性

@Autowired注解入static属性时，出现NullPointerException异常。

使用构造方法可解决：

@Component
public class Test {
    
    private static UserService userService;
    
    @Autowired
    public Test(UserService userService) {
        Test.userService = userService;
    }
    
    public static void test() {
        userService.test();
    }
}

使用@PostConstruct注解解决：

@Component
public class Test {
    
    private static UserService userService;
    
    @Autowired
    private UserService userServiceAdd;
    
    @PostConstruct
    public void beforeInit() {
        userService = userServiceAdd;
    }
}