How to create a Spring Interceptor for Spring RESTful web services

Following steps can be taken to implement the interceptor with Spring:

• Implement an interceptor class extending HandlerInterceptorAdapter class. Following is how the code could look like:

  public class LoginInterceptor extends HandlerInterceptorAdapter {
  
      @Override
      public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception exception)
      throws Exception {
      // TODO Auto-generated method stub
  
      }
  
      @Override
      public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
      throws Exception {
      // TODO Auto-generated method stub
  
      }
  
      @Override
      public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
  
          HandlerMethod handlerMethod = (HandlerMethod) handler;
  
          String emailAddress = request.getParameter("emailaddress");
          String password = request.getParameter("password");
  
          if(StringUtils.isEmpty(emailAddress) || StringUtils.containsWhitespace(emailAddress) ||
          StringUtils.isEmpty(password) || StringUtils.containsWhitespace(password)) {
              throw new Exception("Invalid User Id or Password. Please try again.");
          }
  
          return true;
      }
  
  
  }
  

• Implement an AppConfig class or add the addInterceptors in one of the existing Configuration class. Note the path pattern specified with the LoginInterceptor instance

  @Configuration  
  public class AppConfig extends WebMvcConfigurerAdapter  {  
  
      @Override
      public void addInterceptors(InterceptorRegistry registry) {
         registry.addInterceptor(new LoginInterceptor()).addPathPatterns("/account/login");
      }
  } 
  

• Implement the controller method such as following:

  @Controller
  @RequestMapping("/account/login")
  public class LoginController {
  
      @RequestMapping(method = RequestMethod.GET)
      public String login() {
          return "login";
      }
  }