spring+hibernate+struts整合

Question

这里是一个添加user用户的action：
public class AddAction extends Action {
private UserDAO userDAO;
public void setUserDAO(UserDAO userDAO) {
this.userDAO = userDAO;
}//这里能不能不这样写，直接在下面写成 UserDAO userDAO=new UserDAO();行不行？这样在spring配置文件中是不是就不用注入userDAO了？为什么不能这样写呢？


public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
AddForm addForm = (AddForm) form;// TODO Auto-generated method stub
String username=addForm.getUsername();
String password=addForm.getPassword();
User user=new User();
user.setPassword(password);
user.setUsername(username);
userDAO.save(user);
return mapping.findForward("select");
}
}

Answer 1

当然可以不这样写，直接在下面写成 UserDAO userDAO=new UserDAO();
只不过这样的话就是每次请求都要新建一个UserDAO对象，浪费内存嘛，用spring就只创建一个对象实例啊