Cannot Autowire Service in HandlerInterceptorAdapter [duplicate]

Question

I'm getting a NullPointerException when trying to @Autowire my @Service:

public class PagePopulationInterceptor extends HandlerInterceptorAdapter {     private @Autowired MyService service;      public @Override void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView mav) {         service.savePageView(IPUtils.toLong(request.getRemoteAddr()), request.getRequestURI(), request.getHeader("User-Agent"));         mav.addObject("counter", service.getCounter());     } }  @Configuration @ComponentScan(basePackages = "com.mycompany", excludeFilters = { @ComponentScan.Filter(Configuration.class) }) @PropertySource("classpath:application.properties") @EnableTransactionManagement @EnableWebMvc public class MyConfig extends WebMvcConfigurerAdapter {     public @Override void addInterceptors(InterceptorRegistry registry) {         registry.addInterceptor(new PagePopulationInterceptor());     } }  @Service @Transactional public class MyService {     private @Autowired PageViewDao pageViewDao;      public class Counter {         private long total;         private long today;         private long yesterday;         private long now;          // Getters and setters     }      public void savePageView(long ip, String visitPage, String userAgent) {         PageView obj = new PageView();         obj.setVisitDate(new Date());         obj.setUserAgent(userAgent);         obj.setPage(visitPage);         obj.setIp(ip);          pageViewDao.saveOrUpdate(obj);     }      public Counter getCounter() {         Counter ret = new Counter();         // populate Counter members         return ret;     } } 

EDIT: Here's the Stacktrace:

java.lang.NullPointerException     com.mycompany.util.PagePopulationInterceptor.postHandle(PagePopulationInterceptor.java:22)     org.springframework.web.servlet.HandlerExecutionChain.applyPostHandle(HandlerExecutionChain.java:149)     org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:934)     org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)     org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)     javax.servlet.http.HttpServlet.service(HttpServlet.java:621)     org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)     javax.servlet.http.HttpServlet.service(HttpServlet.java:728)     org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)     org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 

Answer 1

That's because Spring isn't managing your PagePopulationInterceptor instance. You are creating it yourself in the below code

public @Override void addInterceptors(InterceptorRegistry registry) {     registry.addInterceptor(new PagePopulationInterceptor()); } 

change that to

@Bean public PagePopulationInterceptor pagePopulationInterceptor() {     return new PagePopulationInterceptor(); }  public @Override void addInterceptors(InterceptorRegistry registry) {     registry.addInterceptor(pagePopulationInterceptor()); } 

In this way, Spring will manage the lifecycle of the PagePopulationInterceptor instance since it's generated from a @Bean method. Spring will scan it for @Autowired targets and inject them.

This assumes that PagePopulationInterceptor is in a package to be @ComponentScaned.