总体理解

• 听起来如果是权限控制时使用ThreadLocal，并不是出于减少查询Redis数据库的目的，而是为了保证数据完整性，Thread线程独占某个资源避免高并发时出现数据异常和串号的情况。

Controller

@RestController
@RequestMapping("/threadLocal")
public class ThreadLocalController {
    @RequestMapping("/test")
    @ResponseBody
    public Long test() {
        return RequestHolder.getId();
    }
}

RequestHolder

public class RequestHolder {
    private final static ThreadLocal<Long> requestHolder = new ThreadLocal<>();
    public static void add(long id) {
        requestHolder.set(id);
    }
    public static Long getId() {
        return requestHolder.get();
    }
    public static void remove() {
        requestHolder.remove();
    }
}

HttpFilter

@Slf4j
public class HttpFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        log.info("do filter, {}, {}", Thread.currentThread().getId(), request.getServletPath());
        //在ThreadLocal中添加当前线程的id
        RequestHolder.add(Thread.currentThread().getId());
        filterChain.doFilter(servletRequest, servletResponse);
    }
    @Override
    public void destroy() {
    }
}

HttpInterceptor

• 真实使用的时候

  @Slf4j
  public class HttpInterceptor extends HandlerInterceptorAdapter {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("preHandle");
        return true;
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        log.info("ThreadId:"+RequestHolder.getId());
        RequestHolder.remove();
        log.info("afterCompletion");
        return;
    }
  }

DemoApplication

@SpringBootApplication(scanBasePackages = "Controller")
public class DemoApplication extends WebMvcConfigurerAdapter {
    public static void main(String[] args)
    {
        SpringApplication.run(DemoApplication.class, args);
    }
    @Bean
    public FilterRegistrationBean httpFilter() {
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        registrationBean.setFilter(new HttpFilter());
        registrationBean.addUrlPatterns("/threadLocal/*");
        return registrationBean;
    }
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new HttpInterceptor()).addPathPatterns("/**");
    }
}