Spring boot #Autowired is not working in the servlet duriing the server startup - spring

Question

I have servlet whose load on startup property is '1', in this servlet I have to cache database entries during the application server startup.
In this servlet I am calling the CacheService which retrieves the db objects, its annotated with #Autowired annoatation, during the application startup the CacheService object is null.I have annotated the CacheService with #Service annotation. The #Autowired annotation is not working.
#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;
}
}
Could some body help me on this...?

Answer 1

You should do some additional work for this. You have to talk to beanFactory-like spring component and ask it to make that particular instance an eligible bean. AutowireCapableBeanFactory should do the trick.
Here is a simple example based on code you have provided
#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%

Answer 2

You're creating the servlet by using new so you need to provide its dependencies. Since you're using a mix of annotation and java code configuration you can accomplish it like this:
public class StartupServlet extends HttpServlet {
private CacheService cacheService;
public StartupServlet(CacheService cacheService) {
this.cacheService = cacheService;
}
// ... rest of servlet
}
Main class:
#Bean
ServletRegistrationBean myServletRegistration (CacheService cacheService) { // <<<--- cacheService will be provided here by Spring because it's annotated
ServletRegistrationBean srb = new ServletRegistrationBean();
srb.setServlet(new StartupServlet(cacheService));
srb.setUrlMappings(Arrays.asList("/path2/*"));
srb.setLoadOnStartup(1);
return srb;
}