Springboot @Autowired 无法注入问题

特别提醒：一定要注意文件结构

　　WebappApplication 一定要在包的最外层，否则Spring无法对所有的类进行托管，会造成@Autowired 无法注入。

1.　　添加工具类获取在 Spring 中托管的 Bean

　　（1）工具类

package com.common;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

/**
 * @program: IPC_1P
 * @description: 获取在spring中托管的bean
 * @author: johnny
 * @create: 2018-08-03 16:24
 **/
public class SpringContextUtil {
    private static ApplicationContext applicationContext; // Spring应用上下文

    // 下面的这个方法上加了@Override注解，原因是继承ApplicationContextAware接口是必须实现的方法

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

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    public static Object getBean(String name) throws BeansException {
        return applicationContext.getBean(name);
    }

    public static Object getBean(String name, Class requiredType)
            throws BeansException {

        return applicationContext.getBean(name, requiredType);
    }

    public static boolean containsBean(String name) {
        return applicationContext.containsBean(name);
    }

    public static boolean isSingleton(String name)
            throws NoSuchBeanDefinitionException {
        return applicationContext.isSingleton(name);
    }

    public static Class getType(String name)
            throws NoSuchBeanDefinitionException {
        return applicationContext.getType(name);
    }

    public static String[] getAliases(String name)
            throws NoSuchBeanDefinitionException {
        return applicationContext.getAliases(name);
    }
}

　　（2）使用

　　　　1）程序启动时，实例化 SpringContextUtil

@SpringBootApplication
public class WebappApplication {

    private static ApplicationContext applicationContext;
    public static void main(String[] args) {
        applicationContext = SpringApplication.run(WebappApplication.class, args);

        //
        SpringContextUtil springContextUtil = new SpringContextUtil();
        springContextUtil.setApplicationContext(applicationContext);

        System.out.println("服务器启动测试!");
}

　　　　2）在使用 @Service 的方法中，通过@Autowired 注入，使用SpringcontexUtil 获取Bean上下文

@Autowired
    SenderService senderService;

public class Package_State  {

    @Autowired
    SenderService senderService;

    @Component
    private Package_State() {
        senderService = (SenderService)SpringContextUtil.getBean("senderService");
    }
}

Java 初学，原理理解不很透彻，只针对遇到的问题进行记录，随着学习的深入随时修改