拦截器

如果我们要用拦截器，拦截某个接口需要校验，还需要再拦截器方法写上/admin/** 等等，这样代码不可维护，不可扩展

我们可以使用注解来指定这个接口是否要拦截，使用到Spring的InitializingBean，再系统启动的时候通过注解拿到需要拦截的接口路径，代码编写一下

注解编写

@Target(TYPE)
@Retention(RUNTIME)
public @interface Interceptor {
}

接口层编写

@Interceptor
@RestController
@RequestMapping("/admin")
public class AdminController {
}

拦截器编写

public class AdminInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        Object admin = request.getSession().getAttribute("admin");
        // session是空的 直接跳转登录
        if (adminLogin == null) {
            return false;
        } 
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    }

重点

@Configuration
public class InterceptorConfiguration implements WebMvcConfigurer, InitializingBean {

    private Set<String> pathPatterns = new HashSet<>();

    @Bean
    public AdminInterceptor adminInterceptor() {
        return new AdminInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 需要拦截的路径
        String[] addPathPatterns = new String[pathPatterns.size()];
        pathPatterns.toArray(addPathPatterns);
        // 循环每个路径添加/**
        for (int i = 0; i < addPathPatterns.length; i++) {
            addPathPatterns[i] = addPathPatterns[i] + "/**";
        }
        // 不需要拦截的路径
        String[] excludePathPatterns = {"/login"};
        // 注册登录拦截器，拦截除excludePathPatterns参数以外的所有请求
        registry.addInterceptor(adminInterceptor()).addPathPatterns(addPathPatterns)
                .excludePathPatterns(excludePathPatterns);
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        // 解析具体路径指定的具体资源、ymal,properties,springboot使用pathMatchingResourcePatternResolver扫描装载到自动注册
        PathMatchingResourcePatternResolver pathMatchingResourcePatternResolver = new PathMatchingResourcePatternResolver();
        // 元数据集缓存读取工厂，用于读取元数据
        CachingMetadataReaderFactory cachingMetadataReaderFactory = new CachingMetadataReaderFactory();
        Resource[] resources = pathMatchingResourcePatternResolver.getResources("classpath*:com/baerwang/controller/*.class");
        for (Resource resource : resources) {
            // 元数据集缓存工厂读取的数据
            MetadataReader reader = cachingMetadataReaderFactory.getMetadataReader(resource);
            String className = reader.getClassMetadata().getClassName();
            // 获取上下文类加载器
            ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
            Class<?> aClass = contextClassLoader.loadClass(className);
            boolean annotationPresent = aClass.isAnnotationPresent(Interceptor.class);
            if (annotationPresent) {
                RequestMapping annotation = aClass.getAnnotation(RequestMapping.class);
                if (annotation != null) {
                    pathPatterns.addAll(Arrays.asList(annotation.value()));
                } else {
                    Method[] declaredMethods = aClass.getDeclaredMethods();
                    for (Method declaredMethod : declaredMethods) {
                        // 如果接口有get,post,put,delete/mapping等等，需要自行判断添加
                        RequestMapping field = declaredMethod.getAnnotation(RequestMapping.class);
                        if (field != null) {
                            pathPatterns.addAll(Arrays.asList(field.value()));
                        }
                    }
                }
            }
        }
    }
}