首先需要知道的是，容器中的元件，也就是你添加了諸如@Component , @Service , @Controller以及@Repository等等註解，在容器啟動的時候是會掃描標註這些註解的類建立bean並放入容器中。

如果該類中的成員變數上使用了諸如@Autowired和@Resource註解時，容器將會找對應的bean並注入–依賴注入。

而在多執行緒例項中使用@Autowired註解有時得不到物件，為什麼呢？

執行緒類例項如下：

@Component
public class TestThread extends Thread{

    private static final
 
 Logger log = LoggerFactory.getLogger(TestThread.class);

    @Autowired
    ISysBoundUserExtendDao boundUserExtendDao;

    @Autowired
    SysBoundUserMapper boundUserMapper;

    int pageBegin;

    int pageEnd;

    public TestThread( int pageEnd,int pageBegin) {
        super();
        this.pageEnd = pageEnd;
        this
 
.pageBegin = pageBegin;
        log.debug("pageBegin : "+pageBegin+" , pageEnd : "+pageEnd);
    }
    public TestThread() {
        super();
    }
    public TestThread(ISysBoundUserExtendDao boundUserExtendDao, SysBoundUserMapper boundUserMapper, int pageEnd,
            int pageBegin) {
        super
 
();
        this.boundUserExtendDao = boundUserExtendDao;
        this.boundUserMapper = boundUserMapper;
        this.pageEnd = pageEnd;
        this.pageBegin = pageBegin;
        log.debug("pageBegin : "+pageBegin+" , pageEnd : "+pageEnd);
    }

    public void run(){
        String result = "";
        Integer pageSize=1000;
        Map<String, Object> queryMap = new HashMap<>();
        for(int i=pageBegin;i<pageEnd;i++){
            queryMap.put("page", i);
            queryMap.put("pageSize", pageSize);
            log.debug("開始獲取第"+i+"頁使用者...");
            List<SysBoundUser> boundUserList = boundUserExtendDao.getBoundUserList(queryMap);
            //...
            }
        }
}

使用了@Component和@Autowired註解。

此時建立多執行緒如下：

    @RequestMapping(value="checkUser2",produces="application/json;charset=utf-8")
    @ResponseBody
    public String checkUser2(){
        String result = "";
        TestThread testThread1 = new TestThread(4, 3);
        testThread1.start();
        TestThread testThread2 = new TestThread( 5, 4);
        testThread2.start();
        TestThread testThread3 = new TestThread(6, 5);
        testThread3.start();
        TestThread testThread4 = new TestThread(7, 6);
        testThread4.start();
        TestThread testThread5 = new TestThread(8, 7);
        testThread5.start();
        return result;
    }

會發現，在run()方法中boundUserExtendDao為null！！！

這是因為建立多執行緒時，是new的物件例項，非容器掃描時自動建立的物件例項！！！而你建立執行緒的時候並沒有傳入boundUserExtendDao。

如果獲取的是容器建立的TestThread，那麼肯定有mapper和dao:

那麼如何在多執行緒中使用boundUserExtendDao呢？

答：建立的時候傳入boundUserExtendDao例項！

例項如下，此時run方法中可以正確拿到mapper和dao：

@Controller
@RequestMapping("/test")
public class TestDataController {

    private static final Logger log = LoggerFactory.getLogger(TestDataController.class);

    @Autowired
    ISysBoundUserExtendDao boundUserExtendDao;

    @Autowired
    SysBoundUserMapper boundUserMapper;


    @RequestMapping(value="checkUser2",produces="application/json;charset=utf-8")
    @ResponseBody
    public String checkUser2(){
        String result = "";
        TestThread testThread1 = new TestThread( boundUserExtendDao, boundUserMapper,4, 3);
        testThread1.start();
        TestThread testThread2 = new TestThread( boundUserExtendDao, boundUserMapper,5, 4);
        testThread2.start();
        TestThread testThread3 = new TestThread(boundUserExtendDao, boundUserMapper, 6, 5);
        testThread3.start();
        TestThread testThread4 = new TestThread(boundUserExtendDao, boundUserMapper, 7, 6);
        testThread4.start();
        TestThread testThread5 = new TestThread(boundUserExtendDao, boundUserMapper, 8, 7);
        testThread5.start();
        return result;
    }