拦截器和过滤器有点像，只不过过滤器是servlet的技术，拦截器是SpringMVC的。

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入门案例

制作拦截器功能类

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@Component
public class ProjectInterceptor implements HandlerInterceptor {
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle");
        return true;
    }

    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle");
    }

    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion");
    }
}

在配置类中添加

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@Configuration
@ComponentScan({"cola.controller","cola.config"})
@EnableWebMvc
public class SpringMvcConfig implements WebMvcConfigurer{
    @Autowired
    private ProjectInterceptor projectInterceptor;

    @Override
    public 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
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books","/books/*");
    }
}

控制台输出

可以看出三个方法执行的顺序。

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preHandle
[INFO] {dataSource-1} inited
postHandle
afterCompletion

注意，若preHandle方法返回的是false，则会在该方法执行完成后停止。

拦截器参数

拦截器链工作流程