拦截器HandlerInterceptor

1、拦截器接口三个方法

• preHandle目标方法执行之前
• postHandle目标方法执行完成之后，页面处理之前
• afterCompletion最终页面

2、登录的一个拦截功能添加

（1）创建一个登录拦截器

@Slf4j
public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info(request.getRequestURI());
        HttpSession session = request.getSession();
        Object user = session.getAttribute("user");
        if (user == null || !(user instanceof User) || !StringUtils.hasText(((User)user).getUsername())){
            //拦截需要登录
            response.sendRedirect("/login");
            session.setAttribute("msg","请重新登录");
            return false;
        }
        //false是拦截
        return true;
    }
}

（2）把拦截器注册到Spring容器中

• 静态资源我们要注意不能拦截，所以使用excludePathPatterns排除拦截页面

• addPathPatterns使用”/**”匹配所有路径

  @Configuration
  public class MyConfig {
    @Bean
    public WebMvcConfigurer getWebMvcConfigurer(){
        WebMvcConfigurer webMvcConfigurer = new WebMvcConfigurer() {
            @Override
            public void addInterceptors(InterceptorRegistry registry) {
                registry.addInterceptor(new LoginInterceptor())
                        .addPathPatterns("/**")
                        .excludePathPatterns("/login")
                        .excludePathPatterns("/error")
                        .excludePathPatterns("/css/**")
                        .excludePathPatterns("/js/**")
                        .excludePathPatterns("/images/**")
                        .excludePathPatterns("/fonts/**");
            }
        };
        return webMvcConfigurer;
    }
  }