spring scope與線程之間的關(guān)系？

@oxf1992

按照你所說，在controller 中執(zhí)行休眠的時候，符合差不多同時執(zhí)行的規(guī)律
但是如果在controller 調(diào)用service，service執(zhí)行休眠的時候，兩個間隔時間比較長，但又小于休眠時間，具體代碼如下

@RestController
@RequestMapping("/test")
public class TestController {
    private static final Logger logger = LoggerFactory.getLogger(TestController.class);
    @Autowired
    private IUserService userService;

    @GetMapping("/user")
    public Object testUser() {
        logger.info("testController:{}", this.toString());
        logger.info("userService:{}", userService.toString());
        userService.get(1l);
        return "ok";
    }

    @RequestMapping("/foo2")
    public Object foo2(HttpServletRequest request) throws InterruptedException {
        String param = request.getParameter("p");
        logger.error("param:{}", param);
        long start = System.currentTimeMillis();
        Thread.sleep(10000);
        long end = System.currentTimeMillis();
        logger.error("time:{}", end - start);
        return end - start;
    }
}


    @Override
    public void get(Long id) {
        logger.error("get start...{}", this.toString());
        try {
            Thread.sleep(30000l);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        logger.error("get end...{}", this.toString());
    }

結(jié)果如下：

2018-03-28 15:53:04.559  INFO 21776 --- [io-8080-exec-10] c.e.m.web.controller.TestController      : testController:com.example.multimodule.web.controller.TestController@189ebbd
2018-03-28 15:53:04.559  INFO 21776 --- [io-8080-exec-10] c.e.m.web.controller.TestController      : userService:com.example.multimodule.service.service.impl.UserServiceImpl@2a12ba65
2018-03-28 15:53:04.559 ERROR 21776 --- [io-8080-exec-10] c.e.m.s.service.impl.UserServiceImpl     : get start...com.example.multimodule.service.service.impl.UserServiceImpl@2a12ba65
2018-03-28 15:53:25.665  INFO 21776 --- [nio-8080-exec-4] c.e.m.web.controller.TestController      : testController:com.example.multimodule.web.controller.TestController@189ebbd
2018-03-28 15:53:25.665  INFO 21776 --- [nio-8080-exec-4] c.e.m.web.controller.TestController      : userService:com.example.multimodule.service.service.impl.UserServiceImpl@2a12ba65
2018-03-28 15:53:25.665 ERROR 21776 --- [nio-8080-exec-4] c.e.m.s.service.impl.UserServiceImpl     : get start...com.example.multimodule.service.service.impl.UserServiceImpl@2a12ba65
2018-03-28 15:53:34.559 ERROR 21776 --- [io-8080-exec-10] c.e.m.s.service.impl.UserServiceImpl     : get end...com.example.multimodule.service.service.impl.UserServiceImpl@2a12ba65
2018-03-28 15:53:55.665 ERROR 21776 --- [nio-8080-exec-4] c.e.m.s.service.impl.UserServiceImpl     : get end...com.example.multimodule.service.service.impl.UserServiceImpl@2a12ba65
2018-03-28 15:54:01.853 ERROR 21776 --- [nio-8080-exec-8] c.e.m.web.controller.TestController      : param:aaaaa
2018-03-28 15:54:03.788 ERROR 21776 --- [nio-8080-exec-5] c.e.m.web.controller.TestController      : param:bbbb
2018-03-28 15:54:11.854 ERROR 21776 --- [nio-8080-exec-8] c.e.m.web.controller.TestController      : time:10000
2018-03-28 15:54:13.788 ERROR 21776 --- [nio-8080-exec-5] c.e.m.web.controller.TestController      : time:10000

可以看到兩次執(zhí)行foo2請求，基本是同時執(zhí)行，但兩次執(zhí)行user，中間間隔時間較長

我個人認為是你把單例和線程安全搞混了，單例并不意味著線程安全，多線程同時訪問單例同樣存在并發(fā)問題，除非你手動加鎖。下面通過一個例子說明，你覺得最后 count 會是多少？

public class Demo {
    private int count;

    public void add() {
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        this.count++;
    }

    public static void main(String[] args) {
        Demo d = new Demo();

        // 8個線程同時訪問同一個 demo
        new Thread(() -> {d.add();}).start();
        new Thread(() -> {d.add();}).start();
        new Thread(() -> {d.add();}).start();
        new Thread(() -> {d.add();}).start();
        new Thread(() -> {d.add();}).start();
        new Thread(() -> {d.add();}).start();
        new Thread(() -> {d.add();}).start();
        new Thread(() -> {d.add();}).start();

        // 主線程休眠 2 s ，等其他線程執(zhí)行結(jié)束
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(d.count);
    }
}