Unable to autowire the service inside my authentication filter in Spring

Question

I am trying to authenticate user by token, But when i try to auto wire one my services inside the AuthenticationTokenProcessingFilter i get null pointer exception. because autowired service is null , how can i fix this issue ?

My AuthenticationTokenProcessingFilter class

@ComponentScan(basePackages = {"com.marketplace"}) public class AuthenticationTokenProcessingFilter extends GenericFilterBean {      @Autowired     @Qualifier("myServices")     private MyServices service;      public void doFilter(ServletRequest request, ServletResponse response,             FilterChain chain) throws IOException, ServletException {         @SuppressWarnings("unchecked")         Map<String, String[]> parms = request.getParameterMap();          if (parms.containsKey("token")) {             try {                 String strToken = parms.get("token")[0]; // grab the first "token" parameter                  User user = service.getUserByToken(strToken);                 System.out.println("Token: " + strToken);                  DateTime dt = new DateTime();                 DateTimeFormatter fmt = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss");                 DateTime createdDate = fmt.parseDateTime(strToken);                 Minutes mins = Minutes.minutesBetween(createdDate, dt);                   if (user != null && mins.getMinutes() <= 30) {                     System.out.println("valid token found");                      List<GrantedAuthority> authorities = new ArrayList<GrantedAuthority>();                     authorities.add(new SimpleGrantedAuthority("ROLE_ADMIN"));                      UsernamePasswordAuthenticationToken token = new UsernamePasswordAuthenticationToken(user.getEmailId(), user.getPassword());                     token.setDetails(new WebAuthenticationDetails((HttpServletRequest) request));                     Authentication authentication = new UsernamePasswordAuthenticationToken(user.getEmailId(), user.getPassword(), authorities); //this.authenticationProvider.authenticate(token);                      SecurityContextHolder.getContext().setAuthentication(authentication);                 }else{                     System.out.println("invalid token");                 }             } catch(Exception e) {                 e.printStackTrace();             }         } else {             System.out.println("no token found");         }         // continue thru the filter chain         chain.doFilter(request, response);     } } 

I Tried adding follwing in my AppConfig

@Bean(name="myServices")     public MyServices stockService() {         return new MyServiceImpl();     } 

My AppConfig Annotations are

@Configuration @EnableWebMvc @ComponentScan(basePackages = "com.marketplace") public class AppConfig extends WebMvcConfigurerAdapter { 

Answer 1

You cannot use dependency injection from a filter out of the box. Although you are using GenericFilterBean your Servlet Filter is not managed by spring. As noted by the javadocs

This generic filter base class has no dependency on the Spring org.springframework.context.ApplicationContext concept. Filters usually don't load their own context but rather access service beans from the Spring root application context, accessible via the filter's ServletContext (see org.springframework.web.context.support.WebApplicationContextUtils).

In plain English we cannot expect spring to inject the service, but we can lazy set it on the first call. E.g.

public class AuthenticationTokenProcessingFilter extends GenericFilterBean {     private MyServices service;     @Override     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {         if(service==null){             ServletContext servletContext = request.getServletContext();             WebApplicationContext webApplicationContext = WebApplicationContextUtils.getWebApplicationContext(servletContext);             service = webApplicationContext.getBean(MyServices.class);         }         your code ...         }  } 

Answer 2

I just made it work by adding

SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);

I am unsure why we should do this even when i tried adding explicit qualifier. and now the code looks like

public void doFilter(ServletRequest request, ServletResponse response,             FilterChain chain) throws IOException, ServletException {          SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);          @SuppressWarnings("unchecked")         Map<String, String[]> parms = request.getParameterMap();          if (parms.containsKey("token")) {