SpringMVC interceptors use

Source address

interceptor interceptor

The interceptor is the first door for URL requests. All requests will go through the interceptor first interceptor, and then enter controller.
Next, record a method to intercept all requests that require login to initiate, and redirect illegal requests to the login interface.

xml file basic configuration

<!--配置拦截器, 多个拦截器,顺序执行 -->
<mvc:interceptors>
    <mvc:interceptor>
        <!-- 匹配的是url路径， 如果不配置或/**,将拦截所有的Controller -->
        <mvc:mapping path="/**" />
        <!--resource不拦截-->
        <mvc:exclude-mapping path="/asset/**"/>
        <mvc:exclude-mapping path="/assets/**"/>
        <!--聊天室websocket不拦截-->
        <mvc:exclude-mapping path="/sockjs/websocket"/>
        <mvc:exclude-mapping path="/websocket"/>
        <bean class="com.iss.blog.interceptor.AccessControlInterceptor"/>
    </mvc:interceptor>
    <!-- 当设置多个拦截器时，先按顺序调用preHandle方法，然后逆序调用每个拦截器的postHandle和afterCompletion方法 -->
</mvc:interceptors>
<!-- 静态资源访问（不拦截此目录下的东西的访问）  -->
<mvc:resources location="/asset/"  mapping="/asset/**" />
<mvc:resources location="/assets/"  mapping="/assets/**" />

key implementationHandlerInterceptorAdapter

public abstract class AbstractInterceptor extends HandlerInterceptorAdapter {
    /**
     * 是否有 PublicPage注解
     * @param handlerMethod
     * @return
     */
    protected  boolean isPublicPage(HandlerMethod handlerMethod){
        if (handlerMethod==null)
            return false;
        PublicPage publicPage = handlerMethod.getMethodAnnotation(PublicPage.class);
        if (publicPage!=null){
            return true;
        }
        return false;
    }
    /**
     * 某个请求是否ajax请求
     * @param request
     * @return
     */
    protected boolean isAjaxRequest(HttpServletRequest request){
        String requestType = request.getHeader("X-Requested-With");
        if("XMLHttpRequest".equals(requestType)){
            System.out.println("is AJAX request");
            return true;
        }else{
            System.out.println("is not AJAX request");
            return false;
        }
    }
}


    public class AccessControlInterceptor extends AbstractInterceptor {
    /**
     * 下面这段话参考了某片文章，由于找不回原文，所以参考链接不贴
     * 在业务处理器处理请求之前被调用
     * 如果返回false
     *     从当前的拦截器往回执行所有拦截器的afterCompletion(),再退出拦截器链
     * 如果返回true
     *    执行下一个拦截器,直到所有的拦截器都执行完毕
     *    再执行被拦截的Controller
     *    然后进入拦截器链,
     *    从最后一个拦截器往回执行所有的postHandle()
     *    接着再从最后一个拦截器往回执行所有的afterCompletion()
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        if (handler instanceof  HandlerMethod &&isPublicPage((HandlerMethod) handler)){
            return true;
        }
        if(没有登录){
            PrintWriter out = response.getWriter();
            out.append(
                    "{'resultCode':1012,'resultMessage':'错误的请求'}"
            );
            if (!isAjaxRequest(request)) {
            //这里把请求转发给登录界面
                request.getRequestDispatcher("/login").forward(request, response);
            }
            return false;
        }else
            return true;
    }

    /**
     * 在业务处理器处理请求执行完成后,生成视图之前执行的动作
     * 可在modelAndView中加入数据，比如当前时间
     */
    @Override
    public void postHandle(HttpServletRequest request,
                           HttpServletResponse response, Object handler,
                           ModelAndView modelAndView) throws Exception {
    }

    /**
     * 在DispatcherServlet完全处理完请求后被调用,可用于清理资源等
     *
     * 当有拦截器抛出异常时,会从当前拦截器往回执行所有的拦截器的afterCompletion()
     */
    @Override
    public void afterCompletion(HttpServletRequest request,
                                HttpServletResponse response, Object handler, Exception ex)
            throws Exception {

    }
}

defined annotation

@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface PublicPage {
    String value() default "";
}

In this way, @RequestMappingadding @PublicPageit to the above means that the route can be requested without logging in, otherwise it can be requested after logging in. For
example, the login page:

@PublicPage
@RequestMapping("/login")
public  String loginPage(){
    return "frontend/account/login";
}

Must be an ajax request to access

 @RequestMapping(value = "/registerValidate",headers = { "X-Requested-With=XMLHttpRequest" })