static方法调用mapper接口出现NullPointerException

浅浅的花香味﹌ 2023-09-27 06:28 98阅读 0赞

**关于：springboot工具类中@Autowired注入bean，用static直接修饰，静态方法使用bean时报空指针异常错误**

**一般写法：**

public class DataAnalysis {
        
    
        public static DataAnalysis dataAnalysis;
    
        @Autowired
        private IHlFlyDroneMessageService hlFlyDroneMessageService;
        @Autowired
        private HlFlyDroneInfoMapper hlFlyDroneInfoMapper;
        @Autowired
        private HlFlyPlanMapper hlFlyPlanMapper;
        @Autowired
        private HlFlyRelationMapper hlFlyRelationMapper;

**引用：**

QueryWrapper<HlFlyDroneInfo> queryWrapper = new QueryWrapper<>();
            queryWrapper.eq("aircraft_name", hlFlyDroneMessage.getAircraftName());
            List<HlFlyDroneInfo> hlDroneInfoList = hlFlyDroneInfoMapper.selectList(queryWrapper);

此时会报：NullPointerException异常

**解决方案：**  
1、该类使用@Component注解

2、添加一个本类类型的静态字段

3、创建一个初始化方法，贴上@PostConstruct 标签，用于注入bean

4、创建方法调用mapper或service接口

5、最后直接在普通类中调用即可

@Component
    public class DataAnalysis {
        
    
        public static DataAnalysis dataAnalysis;
    
        @Autowired
        private IHlFlyDroneMessageService hlFlyDroneMessageService;
        @Autowired
        private HlFlyDroneInfoMapper hlFlyDroneInfoMapper;
        @Autowired
        private HlFlyPlanMapper hlFlyPlanMapper;
        @Autowired
        private HlFlyRelationMapper hlFlyRelationMapper;
    
        @PostConstruct
        public void init() {
        
            dataAnalysis = this;
            dataAnalysis.hlFlyDroneInfoMapper = this.hlFlyDroneInfoMapper;
            dataAnalysis.hlFlyDroneMessageService = this.hlFlyDroneMessageService;
            dataAnalysis.hlFlyPlanMapper = this.hlFlyPlanMapper;
            dataAnalysis.hlFlyRelationMapper = this.hlFlyRelationMapper;
        }

**引用：**

QueryWrapper<HlFlyDroneInfo> queryWrapper = new QueryWrapper<>();
                    queryWrapper.eq("aircraft_name", hlFlyDroneMessage.getAircraftName());
                    List<HlFlyDroneInfo> hlDroneInfoList = dataAnalysis.hlFlyDroneInfoMapper.selectList(queryWrapper);