springboot拦截器的使用

1.创建一个类，继承与HandlerInterceptor，并实现3个方法。在preHandle方法中，调用controller组件前被调用，可以在此做业务逻辑。下面是每次调用前，都进行登录的判断。

public class LoginInterceptor implements HandlerInterceptor {

    private Logger LOGGER = LoggerFactory.getLogger(LoginInterceptor.class);

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        LOGGER.info("preHandle");
        Object object = request.getSession().getAttribute("name");
        if(null!=object&&object instanceof String){
            String user = (String)object;
            if((user.equals("fangdingjie"))){
                LOGGER.info("登录成功");
                return true;
            }
        }
        LOGGER.info("请登录");
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        LOGGER.info("postHandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        LOGGER.info("afterCompletion");
    }
}

2.在App启动类中创建一个子类，继承于WebMvcConfigurationSupport，并使用@Configuration注解.
addPathPatterns对指定的路径进行拦截，"/**"表示所有路径都进行拦截
excludePathPatterns表示不拦截的路径

 @Configuration
    static class WebMvcConfigurer extends WebMvcConfigurationSupport {
        //增加拦截器
        public void addInterceptors(InterceptorRegistry registry){
            registry.addInterceptor(new LoginInterceptor())    //指定拦截器类
                    .addPathPatterns("/**") //指定该类拦截的url
                    .excludePathPatterns("/login");;       //不拦截
        }
    }