攔截器可以攔截請求也可以攔截響應。使用攔截器的步驟如下： <br/> **1. 實現接口HandlerInterceptor** ```java public class CustomHandlerInterceptor implements HandlerInterceptor { /** * 在請求到達目標方法之前該方法首先被執行 * * @param request * @param response * @param handler * @return 返回true則允許通過，false則攔截 * @throws Exception */ @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { System.out.println("preHandle：" + request.getRequestURI()); return true; } /** * 在后端響應數據到前端之前該方法被調用 * * @param request * @param response * @param handler * @param modelAndView * @throws Exception */ @Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { System.out.println("postHandle"); } /** * 響應完成之后該方法被調用，可以在這個方法中做一些釋放資源的工作 * * @param request * @param response * @param handler * @param ex * @throws Exception */ @Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { System.out.println("afterCompletion"); } } ``` **2. 注冊攔截器并設置攔截規則** *`resources/springmvc-servlet.xml`* ```xml <mvc:interceptors> <mvc:interceptor> <!-- 所有以 /sys/，或 /syo/ 為前綴的請求都會被攔截器攔截，其他的不會被攔截 --> <mvc:mapping path="/sys/**" /> <mvc:mapping path="/syo/**" /> <bean class="com.learn.springmvc02.interceptor.CustomHandlerInterceptor" /> </mvc:interceptor> </mvc:interceptors> ``` **3. controller層** ```java @Controller public class AccountController { @RequestMapping("/sys/account") public String toAccount() { return "account"; } @ResponseBody @PostMapping("/syo/account") public Account getAccount(Account account) { System.out.println(account); return account; } } ``` **4. 測試** 訪問 http://localhost:8080/mvc/sys/account 、http://localhost:8080/mvc/syo/account 這些以`/sys/`、`syo`為前綴的請求將會被攔截。 ``` //攔截器中將會打印如下信息 preHandle：/mvc/syo/account postHandle afterCompletion preHandle：/mvc/sys/account postHandle afterCompletion ```