spring boot 使用@Autowired 空指针异常

最新推荐文章于 2023-04-09 13:51:17 发布

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本文介绍了解决Spring框架中@Autowired注解导致的空指针异常问题的方法。通过在类内部使用静态变量并配合@PostConstruct注解来保持引用，确保了依赖注入的正确性。此外，还提到了检查包扫描路径的重要性。

使用@Autowired注入报空指针异常.

出现异常代码如下:

/**
 * @program: iiossPlatform
 * @description: 发送邮件策略
 * @author: Mr.lxq
 * @create: 2019-03-25 18:00
 **/
@Component
public class EmailDistributionService implements DistributionStrategy{

    @Autowired
    private MailServiceImpl mailService;
    @Autowired
    private UserNotifyRepository userNotifyRepository;
    private static Logger log = LoggerFactory.getLogger(EmailDistributionService.class);

    @Override
    @Async
    public void send(DistributeMessage distributeMessage) {

        log.info("进入到邮箱分发的消息"+distributeMessage.toString());
        int userId = distributeMessage.getUserId();

        log.info("访问数据库实体类>>>>"+userNotifyRepository);

        UserNotify userNotify = proxy.userNotifyRepository.findUserNotifyByUserId(userId);


        String email = userNotify.getEmail();

        String alarmMsg = distributeMessage.getMessage().getAlarmMsg();

        log.info("进入到了邮箱发送服务>>>>>>:"+email+"--"+alarmMsg);

        proxy.mailService.sendSimpleMail(email,"告警提示", alarmMsg);
    }
}

这里会出现注入失败,访问数据库实体类一直获取不到,后来找了公司大佬和网上查找,解决方法如下,使用一个本地变量在类中维持住引用.具体代码如下:

/**
 * @program: iiossPlatform
 * @description: 发送邮件策略
 * @author: Mr.lxq
 * @create: 2019-03-25 18:00
 **/
@Component
public class EmailDistributionService implements DistributionStrategy{

    @Autowired
    private MailServiceImpl mailService;

    @Autowired
    private UserNotifyRepository userNotifyRepository;

    private static EmailDistributionService proxy;

    private static Logger log = LoggerFactory.getLogger(EmailDistributionService.class);

    @PostConstruct
    public void init (){
        proxy=this;
    }
    @Override
    @Async
    public void send(DistributeMessage distributeMessage) {

        log.info("进入到邮箱分发的消息"+distributeMessage.toString());
        int userId = distributeMessage.getUserId();

        log.info("访问数据库实体类>>>>"+proxy.userNotifyRepository);

        UserNotify userNotify = proxy.userNotifyRepository.findUserNotifyByUserId(userId);


        String email = userNotify.getEmail();

        String alarmMsg = distributeMessage.getMessage().getAlarmMsg();

        log.info("进入到了邮箱发送服务>>>>>>:"+email+"--"+alarmMsg);

        proxy.mailService.sendSimpleMail(email,"告警提示", alarmMsg);
    }
}