日常问题---在线程的run方法中使用service层，报空指针异常

末蓝、 2023-03-12 07:23 192阅读 0赞

**问题：**

**     在线程的run方法中使用@Autowired注解获得Service层实例，代码如下：**

public class SchedulerTask implements Runnable{
    	
    	
    	@Autowired
    	private UserService userService;
    
    	
    	
    	@Override
    	public void run() {
    		List<User> list = userService.getAll();		//调用service层
    		for (User user : list) {
    			System.out.println(user);
    		}
    	}
    
    }

**       出现空指针异常：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5MTE1NDY5_size_16_color_FFFFFF_t_70][]

**原因：**

**       在线程的run方法中使用注解@autoware注入的bean，会报空指针异常，原因是因为线程中为了线程安全，防注入。**

**解决：**

**      在bean工厂中拿实例。**

**      编写获取bean实例的工具类组件。**

import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    import org.springframework.stereotype.Component;
    @Component
    public class GetBeanUtil implements ApplicationContextAware {
    
    	private static ApplicationContext applicationContext;
    
    	public void setApplicationContext(ApplicationContext context) {
    		GetBeanUtil.applicationContext = context;
    	}
    
    	public static Object getBean(String name) {
    		return applicationContext.getBean(name);
    	}
    
    	public static ApplicationContext getApplicationContext() {
    		return applicationContext;
    	}
    }

**      在Spring配置文件中配置ServiceImpl实例：**

<bean id="userServiceImpl" class="com.ssm.service.impl.UserServiceImpl" />

**       在run方法中使用工具类拿到Service层实例：**

@Component
    @EnableScheduling
    public class SchedulerTask implements Runnable{
    	
    	
    	@Override
    	public void run() {
    		UserService userService = (UserService) GetBeanUtil.getBean("userServiceImpl");
    		List<User> list = userService.getAll();		//调用service层
    		for (User user : list) {
    			System.out.println(user);
    		}
    	}
    
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5MTE1NDY5_size_16_color_FFFFFF_t_70]: /images/20230312/fc65e6b7656d4edead5c226982253d03.png