Question

我正在学习SPRING，这不是Web应用程序代码;我在字段级别使用@Autowired注释时获得NLP。

Q1）请帮忙出错？
Q2）如果我在班级有@Scope注释;我仍然需要XML bean级别吗？

@Controller
@Scope(value = BeanDefinition.SCOPE_SINGLETON)
public class StreamingController implements psConsolePortListener.Implementation{

    @Autowired
    @Qualifier("scMgr")
    private StreamingControllerManager streamingMgr = null;

    public static void main(String[] args) {
        logger.info("StreamingController testing");
        XmlBeanFactory factory = new XmlBeanFactory (new ClassPathResource(BEAN_FILE)); 
        StreamingController obj = (StreamingController) factory.getBean("streamingController"); 
        obj.streamingMgr.test();
    }

}


@Service
@Scope(value = BeanDefinition.SCOPE_SINGLETON)
@Qualifier("scMgr")
public class StreamingControllerManager {
    /** Logger */
    private static final Logger logger = LoggerFactory.getLogger(StreamingControllerManager.class);

    private StreamingControllerManager(){
        logger.info("StreamingControllerManager is called!!");
    }

    public void test(){
        logger.info("StreamingControllerManager test!!");
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans>
    <context:annotation-config />
    <context:component-scan base-package="com.xxx.streamingController"/>
    <bean id="scMgr" class="com.xxx.streamingController.StreamingControllerManager"> 
    </bean>
    <bean id="streamingController" class="com.xxx.streamingController.StreamingController"> 
    </bean>
</beans>

输出：

Exception in thread "main" java.lang.NullPointerException
        at com.pactolus.streamingController.StreamingController.main(

Answer 1

使用ApplicationContext代替BeanFactory。

public static void main(String[] args) {
    logger.info("StreamingController testing");
    ApplicationContext ctx = new ClassPathXmlApplicationContext(BEAN_FILE);
    StreamingController obj = (StreamingController) ctx.getBean("streamingController"); 
    obj.streamingMgr.test();
}

同时删除<context:annotation-config />已经填充的<context:component-scan />并删除bean声明。您正在使用组件扫描，因此无需声明bean。

基本上离开了你。

<?xml version="1.0" encoding="UTF-8"?>
<beans>
    <context:component-scan base-package="com.xxx"/>
</beans>

NullPointerException：@Autowired未设置字段

1 个答案: