SpringMvc拦截器

 什么是拦截器？

就是你在访问控制层去做业务前后都做一些事，你调用我之前我先看看你有没有这个权限

拦截器和过滤器的区别：

        归属不同：一个是Servlet技术一个是SpringMvc的技术

        拦截的内容不同：过滤器Filter对所有访问进行加强，过滤器Interceptor仅仅针对SpringMvc的访问进行增强

简单的案例

1.声明拦截器的bean 实现 HandlerInterceptor 接口（注意扫描加载bean）

@Component
public class ProjectInterceptor implements HandlerInterceptor {
    //拦截前
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String connection = request.getHeader("Connection");
        //handler里面封装了执行的方法
        System.out.println(handler);
        System.out.println("preHandle..." + connection);
        //false表示终止原始操作
        return true;
    }

    //拦截后
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        //modelAndView封装了页面跳转相关的
        System.out.println("postHandle...");
    }

    //拦截后并且再postHandle之后运行
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        //ex 拿到异常
        System.out.println("afterCompletion...");
    }
}

 2.定义配置类 设置拦截的请求和使用的拦截器

@Configuration
public class SpringMvcSupport extends WebMvcConfigurationSupport {
    @Autowired
    private ProjectInterceptor projectInterceptor;
  
    @Override
    protected void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/pages/**").addResourceLocations("/pages/");
        registry.addResourceHandler("/css/**").addResourceLocations("/css/");
        registry.addResourceHandler("/js/**").addResourceLocations("/js/");
        registry.addResourceHandler("/plugins/**").addResourceLocations("/plugins/");
    }

    @Override
    protected void addInterceptors(InterceptorRegistry registry) {
        //调用/books请求时间拦截 拦截器projectInterceptor
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books","/books/*");
      
}

配置多个拦截器（了解）