Spring boot @Autowired 在服务器启动期间在 servlet 中不起作用

Question

我有一个 servlet，其启动时负载属性为“1”，在此 servlet 中，我必须在应用程序服务器启动期间缓存数据库条目。在此 servlet 中，我调用 CacheService 来检索 db 对象，其使用 @Autowired 注释进行注释，在应用程序启动期间，CacheService 对象为 null。我已使用 @Service 注释对 CacheService 进行注释。 @Autowired 注释不起作用。

@Service
public class CacheService {
    @Autowired
    private IJobsService jobsServiceImpl; 
    public List<Jobs> getALLJobs(){
        List<Jobs> alljobs = jobsServiceImpl.findAllJobs();
        return alljobs;
    }

}


public class StartupServlet extends HttpServlet {

       @Autowired
       private CacheService cacheService; -- object is null not autowired
}

Below is the main class


@EnableCaching
@EnableJpaRepositories(basePackages = {"com.example.demo.repository"})
@EntityScan(basePackages = {"com.example.demo.entity"})
@SpringBootApplication
@ComponentScan(basePackages={"com.example.demo"})
@EnableAutoConfiguration(exclude = {
        org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration.class,
        org.springframework.boot.actuate.autoconfigure.ManagementWebSecurityAutoConfiguration.class})

public class DemoApplication  extends SpringBootServletInitializer implements WebApplicationInitializer{

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Override
       protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
          return builder.sources(DemoApplication.class);
       }

     @Bean
        ServletRegistrationBean myServletRegistration () {
            ServletRegistrationBean srb = new ServletRegistrationBean();
            srb.setServlet(new StartupServlet());
            srb.setUrlMappings(Arrays.asList("/path2/*"));
            srb.setLoadOnStartup(1);
            return srb;
        }
}

有人可以帮我解决这个问题吗？

Answer 1

您应该为此做一些额外的工作。您必须与类似 beanFactory 的 spring 组件通信，并要求它使该特定实例成为合格的 bean。 AutowireCapableBeanFactory 应该可以解决问题。

这是一个基于您提供的代码的简单示例

@SpringBootApplication
public class So44734879Application {

    public static void main(String[] args) {
        SpringApplication.run(So44734879Application.class, args);
    }

    @Autowired
    AutowireCapableBeanFactory beanFactory;

    @Bean
    ServletRegistrationBean myServletRegistration() {
        ServletRegistrationBean srb = new ServletRegistrationBean();
        final StartupServlet servlet = new StartupServlet();
        beanFactory.autowireBean(servlet);  // <--- The most important part
        srb.setServlet(servlet);
        srb.setUrlMappings(Arrays.asList("/path2/*"));
        srb.setLoadOnStartup(1);
        return srb;
    }

    @Bean
    MyService myService() {
        return new MyService();
    }

    public static class MyService {
        String time() {
            return "Time: " + System.currentTimeMillis();
        }
    }

    public static class StartupServlet extends HttpServlet {
        @Autowired
        MyService myService;

        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            final PrintWriter writer = resp.getWriter();
            writer.write(myService.time());
            writer.close();
        }
    }
}

=>

$ curl -XGET localhost:8080/path2
Time: 1498299772141%