Spring编程常见错误–Spring Web篇-14 |Spring Web 过滤器使用常见错误（下）

十四、Spring Web 过滤器使用常见错误（下）（没事别用@WebFilter，问题一堆）

一.@WebFilter 过滤器使用 @Order 无效

1、代码分析

1.主启动类：使用了@ServletComponentScan

@SpringBootApplication
@ServletComponentScan
@Slf4j
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
        log.info("启动成功");
    }
}

2.Controller

@Controller
@Slf4j
public class StudentController {
    @PostMapping("/regStudent/{name)}")
    @ResponseBody
    public String saveUser(String name) throws Exception {
        System.out.println("......用户注册成功");
        return "success";
    }
}

3.Filter：AuthFilter权限认证

@WebFilter
@Slf4j
@Order(2)
public class AuthFilter implements Filter {
    @SneakyThrows
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) {
        if(isPassAuth()){
            System.out.println("通过授权");
            chain.doFilter(request, response);
        }else{
            System.out.println("未通过授权");
            ((HttpServletResponse)response).sendError(401);
        }
    }
    private boolean isPassAuth() throws InterruptedException {
        System.out.println("执行检查权限");
        Thread.sleep(1000);
        return true;
    }
}

4.Filter：TimeCostFilter耗时

@WebFilter
@Slf4j
@Order(1)
public class TimeCostFilter implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("#开始计算接口耗时");
        long start = System.currentTimeMillis();
        chain.doFilter(request, response);
        long end = System.currentTimeMillis();
        long time = end - start;
        System.out.println("#执行时间(ms)：" + time);
    }
}

2、案例解析

上面代码中，使用了@Order,期望按顺序执行，但是实际并非如此。
主要原因就是@WebFilter构建的并非是普通的Bean对象，不会根据Order的值去设置order属性。

3、问题修正

不使用@WebFilter，实现FilterRegistrationBean来配置普通的Bean

@Configuration
public class FilterConfiguration {
    @Bean
    public FilterRegistrationBean authFilter() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new AuthFilter());
        registration.addUrlPatterns("/*");
        registration.setOrder(2);
        return registration;
    }

    @Bean
    public FilterRegistrationBean timeCostFilter() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new TimeCostFilter());
        registration.addUrlPatterns("/*");
        registration.setOrder(1);
        return registration;
    }
}

二.过滤器被多次执行

1、代码分析

@WebFilter
@Slf4j
@Order(2)
@Component
public class AuthFilter implements Filter {
    @SneakyThrows
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain){
        if(isPassAuth()){
            System.out.println("通过授权");
            chain.doFilter(request, response);
        }else{
            System.out.println("未通过授权");
            ((HttpServletResponse)response).sendError(401);
        }
    }
    private boolean isPassAuth() throws InterruptedException {
        System.out.println("执行检查权限");
        Thread.sleep(1000);
        return true;
    }
}

此处代码的关键在于同时使用了@Component和@WebFilter，会生成两种不同的Bean对象。导致Filter被执行了两遍。

2、案例解析

任何通过 @Component 修饰的的类，都可以自动注册到 Spring，且能被 Spring 直接实例化。

3、问题修正

@Component和@WebFilter不能同时使用

@Slf4j
@Order(1)
@Component
public class TimeCostFilter implements Filter {
   //省略非关键代码
}