Special note: pay attention to the file structure

WebappApplication must be at the outermost layer of the package, otherwise Spring cannot host all classes, which will cause @ Autowired to fail to inject.

1. Add a tool class to get the Bean hosted in Spring

(1) tools

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: Get bean s hosted in spring
 * @author: johnny
 * @create: 2018-08-03 16:24
 **/
public class SpringContextUtil {
    private static ApplicationContext applicationContext; // Spring Application context

    // The following method is added@Override Comment, because inheritance ApplicationContextAware Interface is a must

    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) use

1) when the program starts, instantiate 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("Server start test!");
}

2) in the method of using @ Service, inject @ Autowired and use SpringcontexUtil to get the Bean context

@Autowired
    SenderService senderService;

public class Package_State  {

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

Java is a beginner. The understanding of the principle is not very thorough. It only records the problems encountered. It can be modified at any time with the deepening of learning