我是Spring的新手，有一些基本的问题。在下面给出的一个Spring示例中，我注意到EmployeeManager是自动连接的。

问题：

1.没有给出EmployeeManager作用域，所以我假设默认作用域是Singleton，而SpringBean不是线程安全的。这一假设是正确的吗？
1.EmployeeManager定义为Servlet的一部分，可由多个线程访问。假设“Delete”方法被多个线程同时调用，值为“1”、“2”和“3”，并且为每个线程生成相同的EmployeeManager示例(因为它是单例的)，将执行哪个Delete值。Spring如何处理这种情况？

@Controller        
public class EditEmployeeController
{
@Autowired
private EmployeeManager employeeManager;

@RequestMapping(value = "/", method = RequestMethod.GET)
public String listEmployees(ModelMap map)
{
    map.addAttribute("employee", new EmployeeEntity());
    map.addAttribute("employeeList", employeeManager.getAllEmployees());
    return "editEmployeeList";
}
@RequestMapping(value = "/add", method = RequestMethod.POST)
public String addEmployee(@ModelAttribute(value="employee") EmployeeEntity employee, BindingResult result)
{
    employeeManager.addEmployee(employee);
    return "redirect:/";
}
@RequestMapping("/delete/{employeeId}")
public String deleteEmplyee(@PathVariable("employeeId") Integer employeeId)
{
    employeeManager.deleteEmployee(employeeId);
    return "redirect:/";
}
public void setEmployeeManager(EmployeeManager employeeManager) {
    this.employeeManager = employeeManager;
}
}

员工经理-

public interface EmployeeManager {
    public void addEmployee(EmployeeEntity employee);
    public List<EmployeeEntity> getAllEmployees();
    public void deleteEmployee(Integer employeeId);
}

@Service
public class EmployeeManagerImpl implements EmployeeManager
{
    @Autowired
    private EmployeeDAO employeeDAO;
    @Override
    @Transactional
    public void addEmployee(EmployeeEntity employee) {
        employeeDAO.addEmployee(employee);
    }
    @Override
    @Transactional
    public List<EmployeeEntity> getAllEmployees() {
        return employeeDAO.getAllEmployees();
    }
    @Override
    @Transactional
    public void deleteEmployee(Integer employeeId) {
        employeeDAO.deleteEmployee(employeeId);
    }
    public void setEmployeeDAO(EmployeeDAO employeeDAO) {
        this.employeeDAO = employeeDAO;
    }
}