springboot中的拦截器的使用

实现拦截器需要实现HandlerInterceptor接口,接口中有三个方法用于网页加载的不同阶段
首先写一个拦截器的类LoginInterceptor

public class LoginInterceptor implements HandlerInterceptor {
    //目标方法执行之前
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //登陆检查逻辑
        HttpSession session = request.getSession();

        Object loginUser = session.getAttribute("loginUser");
        if(loginUser != null){
            //放行
            return true;
        }
        //拦截
        request.setAttribute("msg","请先登陆");
        request.getRequestDispatcher("/login").forward(request,response);
        return false;
    }

    //目标方法执行完成以后
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }

    //页面渲染以后
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

    }
}

之后在webmvc配置类中对拦截器进行配置,所有的mvc配置类需要实现WebMvcConfigurer接口，在WebMvcConfigurer接口中有一个方法是addInterceptors,用来添加拦截器

@Configuration
public class MyWebConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**") //默认拦截的请求 一般都是些/**
                .excludePathPatterns(
                        "/",
                        "/login",
                        "/css/**",
                        "/fonts/**",
                        "/images/**",
                        "/js/**"
                );//放行的内容
    }
}