Spring Boot手动注入Bean

应用场景

Spring Boot项目中，我们可能遇到@Autowired注入对象为null的问题，可能的原因包含：

（1）当前类的初始化在注入类注入之前
（2）多线程环境，新创建的线程中，是不能自动注入Bean/Service的

此时就需要手动注入Bean

手动获取Bean的工具类

原理，在项目启动时获取到Spring Boot上下文，从上下文中获取到Bean

/**
 * 接通过Spring 上下文获取SpringBean
 * @author yezhou
 * @version 1.0
 * @date 2019/8/15 18:39
 */
@Component
public class ApplicationContextUtil implements ApplicationContextAware {
    // Spring Boot应用上下文环境
    private static ApplicationContext applicationContext;

    /**
     * 实现ApplicationContextAware接口的回调方法，设置上下文环境
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext)
            throws BeansException {
        ApplicationContextUtil.applicationContext = applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    /**
     * 获取对象：这里重写getBean方法，起主要作用
     * example: getBean("userService")  //注意： 类名首字母一定要小写！
     */
    public static Object getBean(String beanId) throws BeansException {
        return applicationContext.getBean(beanId);
    }
}

在超前初始化类或线程类中手动获取Bean/Service

超前初始化类

@Component(value = "UserAuthDetailsService")
public class UserAuthDetailsService implements UserDetailsService {

public class SMSCodeTokenGranter extends AbstractTokenGranter {
    private static final String GRANT_TYPE = "sms_code";

    private UserAuthDetailsService authUserDetailsService;

    public SMSCodeTokenGranter(AuthorizationServerTokenServices tokenServices,
                                  ClientDetailsService clientDetailsService, OAuth2RequestFactory requestFactory) {
        super(tokenServices, clientDetailsService, requestFactory, GRANT_TYPE);
    }

    @Override
    protected OAuth2Authentication getOAuth2Authentication(ClientDetails client,
                                                           TokenRequest tokenRequest) {
        Map<String, String> parameters = new LinkedHashMap<String, String>(tokenRequest.getRequestParameters());
        String userMobileNo = parameters.get("username");  //客户端提交的用户名
        String smsCode = parameters.get("sms_code");  //客户端提交的验证码

        authUserDetailsService = (UserAuthDetailsService) ApplicationContextUtil.getBean("UserAuthDetailsService");
        UserDetails user = authUserDetailsService.loadUserByUsername(userMobileNo);

线程类

public class SdReleaseReview implements Runnable {
    private CalendarService calendarService;

    public SdReleaseReview() {
        this.calendarService=(CalendarService)SpringContextUtil.getBean("calendarService");
    }

    @Override
    public void run() {
        try {
            ...
            FactoryCalendar factoryCalendar = calendarService.getByExistDate("2000", today);
            ...
        } catch (Exception e) {
            ...
        }
    }
}