@Slf4j
@RestController
public class DemoController {
    @GetMapping
    public String testStr(String str) {
        String key = UUID.randomUUID().toString();
        log.info("testStr start {} {}", str, key);
        synchronized (str.intern()) {
            log.info("testStr in {} {}", str, key);
            Thread.sleep(5000);
        }
        log.info("testStr end {} {}", str, key);
        return str;
    }
}

当我有两个要求的时候 ?str=aaa ，日志如下所示：

testStr start aaa 3bbb03e3-84d9-4816-b275-de59657bd810
 testStr in aaa 3bbb03e3-84d9-4816-b275-de59657bd810
... after 5 sec
 testStr end aaa 3bbb03e3-84d9-4816-b275-de59657bd810
 testStr start aaa b4f07a65-e37e-4471-be79-877a8d529f04
 testStr in aaa b4f07a65-e37e-4471-be79-877a8d529f04
... after 5 sec
 testStr end aaa b4f07a65-e37e-4471-be79-877a8d529f04

但我觉得应该是

testStr start aaa 3bbb03e3-84d9-4816-b275-de59657bd810
 testStr in aaa 3bbb03e3-84d9-4816-b275-de59657bd810
 testStr start aaa b4f07a65-e37e-4471-be79-877a8d529f04
... after 5sec
 testStr in aaa b4f07a65-e37e-4471-be79-877a8d529f04
 testStr end aaa 3bbb03e3-84d9-4816-b275-de59657bd810
... after 5 sec
 testStr end aaa b4f07a65-e37e-4471-be79-877a8d529f04

不同的部分 testStr start... 应在5秒前记录。
我错过什么了吗？
顺便说一句，我用简单的main测试这些代码，没有spring的东西，然后一切都按预期工作。
主代码

public static void main(String[] args) {
        DemoController demoController = new DemoController();
        new Thread(()->{
            String result = demoController.testStr("aaa");
            log.info("result1 {}", result);
        }).start();
        new Thread(()->{
            String result = demoController.testStr("aaa");
            log.info("result2 {}", result);
        }).start();
    }