可以使用 JMeter 辅助测试 https://blog.csdn.net/weixin_45014379/article/details/124190381

@RestController
@RequestMapping({"/Test"})
public class test { 

    Logger logger = LoggerFactory.getLogger(this.getClass());
 
    // 使用 Semaphore 并发限制3个 超过阻塞
    private final Semaphore permit = new Semaphore(3, true);


    @GetMapping(value = {"/download"})
    public String download(HttpServletRequest request) {        
        String result = "";
        try {
            // 获取令牌			
            logger.info("锁住 {}", Thread.currentThread().getName());
            permit.acquire();
            logger.info("下载 {}", Thread.currentThread().getName());
            Thread.sleep(5000);
            result = "Success";
        } catch (Exception e) {
            e.printStackTrace();
            return e.getMessage();
        } finally {
            // 释放令牌
            permit.release(); 
            logger.info("释放 {}", Thread.currentThread().getName());
        } 
    }

}

[2022-11-29 14:33:05.042] [http-nio-6201-exec-1] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-1
[2022-11-29 14:33:05.042] [http-nio-6201-exec-1] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-1
[2022-11-29 14:33:05.097] [http-nio-6201-exec-4] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-4
[2022-11-29 14:33:05.097] [http-nio-6201-exec-4] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-4
[2022-11-29 14:33:05.156] [http-nio-6201-exec-3] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-3
[2022-11-29 14:33:05.156] [http-nio-6201-exec-3] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-3
[2022-11-29 14:33:05.204] [http-nio-6201-exec-5] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-5
[2022-11-29 14:33:05.205] [http-nio-6201-exec-5] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-5
[2022-11-29 14:33:05.241] [http-nio-6201-exec-2] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-2
[2022-11-29 14:33:05.241] [http-nio-6201-exec-2] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-2
[2022-11-29 14:33:05.291] [http-nio-6201-exec-6] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-6
[2022-11-29 14:33:05.292] [http-nio-6201-exec-6] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-6
[2022-11-29 14:33:05.341] [http-nio-6201-exec-7] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-7
[2022-11-29 14:33:05.341] [http-nio-6201-exec-7] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-7
[2022-11-29 14:33:05.396] [http-nio-6201-exec-8] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-8
[2022-11-29 14:33:05.396] [http-nio-6201-exec-8] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-8
[2022-11-29 14:33:05.442] [http-nio-6201-exec-9] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-9
[2022-11-29 14:33:05.442] [http-nio-6201-exec-9] [INFO ] com.vipsoft.controller.ReleaseController - 工作 http-nio-6201-exec-9
[2022-11-29 14:33:05.492] [http-nio-6201-exec-10] [INFO ] com.vipsoft.controller.ReleaseController - 锁住 http-nio-6201-exec-10
[2022-11-29 14: