介绍

需要拦截器实现 Spring 提供的 HandlerInterceptor 接口并在配置文件中装配

案例

<!-- 配置拦截器栈 -->
<mvc:interceptors>
<!-- 配置具体的拦截器 -->
    <mvc:interceptor>
        <!-- 设置拦截的请求 -->
        <mvc:mapping path="/**"/>
        <!-- 排除不经过拦截器的请求 -->
        <mvc:exclude-mapping path="/*/*.html"/>
        <mvc:exclude-mapping path="/*/*.js"/>
        <mvc:exclude-mapping path="/login"/>
        <!-- 装配具体的拦截器 -->
        <bean class="top.lldwb.ch09.interceptor.LoginInterceptor"/>
    </mvc:interceptor>
</mvc:interceptors>

/**
 * 登录拦截器
 * 拦截所有请求，如果未登录则返回 401 状态码
 */
@Slf4j
public class LoginInterceptor implements HandlerInterceptor {
    /**
     * 在调用 Controller 的请求方法之前执行，如果此方法返回false，则请求就不会继续往下执行
     *
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  chosen handler to execute, for type and/or instance evaluation
     * @return
     * @throws Exception
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        HttpSession session = request.getSession();
        log.info("preHandle：在调用 Controller 的请求方法之前执行，如果此方法返回false，则请求就不会继续往下执行");
        if (session.getAttribute("user") == null) {
            ResultVo vo = new ResultVo();
            vo.setCode(HttpStatus.UNAUTHORIZED.value());
            response.setContentType("application/json;charset=utf-8");
            String json = new ObjectMapper().writeValueAsString(vo);
            response.getWriter().println(json);
            return false;
        }
//        return HandlerInterceptor.super.preHandle(request, response, handler);
        return true;
    }

    /**
     * 在调用 Controller 的请求方法之后返回之前执行
     * (注意：前提是 Controller 能执行和 preHandle 返回 true)
     *
     * @param request      current HTTP request
     * @param response     current HTTP response
     * @param handler      the handler (or {@link}) that started asynchronous
     *                     execution, for type and/or instance examination
     * @param modelAndView the {@code ModelAndView} that the handler returned
     *                     (can also be {@code null})
     * @throws Exception
     */
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("postHandle：在调用 Controller 的请求方法之后返回之前执行");
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }

    /**
     * 在调用 Controller 的请求方法并返回执行
     *
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the handler (or {@link}) that started asynchronous
     *                 execution, for type and/or instance examination
     * @param ex       any exception thrown on handler execution, if any; this does not
     *                 include exceptions that have been handled through an exception resolver
     * @throws Exception
     */
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
    }
}