SpringBoot中Bean自动注入失败？这里给你解决办法

时间：2025-03-04 20:53:26

中Bean的自动注入

    我们在使用Springboot时，最为常用的bean的注入方式莫过于自动注入了吧，通过在springboot项目中加各种注解即
可使用自动注入，步骤（相对简洁，不过很粗暴）demo如下：
  1. 启动类上加@SpringBootApplication
	@SpringBootApplication
	public class Application {
  	 	 public static void main(String[] args) {
       		 SpringApplication.run(Application .class, args);
    	 }
	}
  1. Controller类上加@RestController
	//controller层
	@RestController
	public class TestController {

   		 @Autowired
    	 private TestService testService;

   		 @RequestMapping("/test")
    	 public String testDemo(String talk){
        	 return testService.talk(talk);
    	 }
	}
  1. Service接口类上加@Service
	//service层
	public interface TestService {
 	     String talk(String talk);
	}

	//serviceImpl
	@Service
	public class TestServiceImpl implements TestService {

  		@Resource
   	    private TestMapper testMapper;
	
   	    @Override
        public String talk(String talk){
            return testMapper.talk();
        }
    }
  1. Mapper类上加@Mapper（启动类上加@MapperScan(basePackages = {“mapper文件所在的路径”})也行）
	//持久层
	@Mapper
	public interface TestMapper {
  	 	 String talk(@Param("talk") String talk);
	}

   当然再牛叉的技术都是不会十全十美的，当你引用一些其他技术到项目中时，有些可能会导致自动注入出现注入失败的情况，
这时候就延申到我们第二种方式啦

中Bean的非自动注入

2.1 首先创建一个SpringContextHolder类，放入到项目中

@Component
@SuppressWarnings("all")
public class SpringContextHolder implements ApplicationContextAware {
    private static ApplicationContext applicationContext;

    public SpringContextHolder() {
    }

    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringContextHolder.applicationContext = applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        assertApplicationContext();
        return applicationContext;
    }

    public static <T> T getBean(String beanName) {
        assertApplicationContext();
        return (T) applicationContext.getBean(beanName);
    }

    public static <T> T getBean(Class<T> requiredType) {
        assertApplicationContext();
        return applicationContext.getBean(requiredType);
    }

    public static <T> List<T> getBeanOfType(Class<T> requiredType) {
        assertApplicationContext();
        Map<String, T> map = applicationContext.getBeansOfType(requiredType);
        return map == null ? null : new ArrayList(map.values());
    }

    public static void autowireBean(Object bean) {
        applicationContext.getAutowireCapableBeanFactory().autowireBean(bean);
    }

    private static void assertApplicationContext() {
        if (applicationContext == null) {
            throw new RuntimeException("applicaitonContext属性为null,请检查是否注入了SpringContextHolder!");
        }
    }
}

2.2在实体类中给主键字段添加注解

	@Data
	public class Test{
	
    	@TableId(type = IdType.AUTO)
    	private Integer id;
    	
   		private String talk;
	}

2.3在使用对应的bean的时候，用一下代码进行创建

	//获取Service
	 TestService testService = SpringContextHolder.getBean(TestService.class);
	//获取Mapper
	 TestMapper testMapper = SpringContextHolder.getBean(TestMapper.class);

到此,我们就已经可以使用我们想要的Bean啦，原理什么的，我看着也很烦，就不在这里说了，CV大法帮助你，哈哈

PS: 内容较为简介，不过稍微一看就能看懂啦，小伙伴们加油哦

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