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如何开始DDD(续)

2024-07-15 20:54:27   222人阅读

上一篇针对用户注册案例简单介绍了如何使用 DDD，接下来我将继续针对这个例子做一下补充。先将User模型丰富起来，因为目前看上去他和贫血模型还没有啥大的区别。

首先还是由领域专家来说明业务，他由提出了用户注册成功后需要完善个人信息，这些信息包括姓名、生日、手机号。还需要用户提供一些联系信息，如果地址，邮编等。那么我们就可以根据业务定义方法了。昨天netfocus兄指正了loginid所产生的歧义，表示认为，所以今天一并修改了一下。

public class AddressInfo{    public AddressInfo(string province, string city, string address, string postcode)    {        this.Province = province;        this.City = city;        this.Address = address;        this.Postcode = postcode;    }    public string Province { get; private set; }    public string City { get; private set; }    public string Address { get; private set; }    public string Postcode { get; private set; }}public class User{    public User(string name, string password, string email)    {        this.Name = name;        this.Password = password;        this.Email = email;    }    public string Id { get; private set; }    public string Name { get; private set; }    public string Password { get; private set; }    public string RealName { get; private set; }    public string Email { get; private set; }    public string Cellphone { get; private set; }    public string Birthday { get; private set; }    public AddressInfo Address { get; private set; }    public void UpdateBasicInfo(string realName, string birthday, string cellphone)    {        this.RealName = realName;        this.Birthday = birthday;        this.Cellphone = cellphone;    }    public void UpdateAddress(AddressInfo address)    {        this.Address = address;    }}

那么前端的代码也很简单

public class UserController{    private readonly IUserRepository _userRepository;    public void SetProfile(FormCollection form)    {        var user = _userRepository.Get(form.Get("id"));        user.UpdateBasicInfo(form.Get("name"), form.Get("birthday"), form.Get("cellphone"));    }    public void SetAddress(FormCollection form)    {        var user = _userRepository.Get(form.Get("id"));        var address = new AddressInfo(form.Get("province"), form.Get("city"),             form.Get("address"), form.Get("postcode"));        user.UpdateAddress(address);    }}

以上的代码很好理解，只是设计了一个AddressInfo的值对象。

接下来将演示一下用户登录验证和修改密码。一般的做法：

public interface IUserRepository{    User GetByName(string loginId);}public class UserController{    private readonly IUserRepository _userRepository;    public UserController(IUserRepository userRepository)    {        this._userRepository = userRepository;    }    public void Logon(FormCollection form)    {        User user = _userRepository.GetByName(form.Get("LoginId"));        if (user == null)            throw new Exception("loginId", "账号不存在。");        if (user.Password != form.Get("Password"))            throw new Exception("password", "密码不正确。");        FormsAuthentication.SetAuthCookie(user.Name, createPersistentCookie);    }}

请注意上述代码比较密码是错误的方式，因为上一篇说明了密码是加过密的。所以要修改一下，首先要注入IEncryptionService，那么就会这样判断

if (user.Password != _encryptionService.Encrypt(form.Get("Password")))

这样会有什么问题呢。目前IEncryptionService的接口相对还比较简单，如果IEncryptionService提供了针对不同业务的好多加密接口，那么前端人员就需要详细了解IEncryptionService的api，增加了复杂度。再对User封装一个方法，然后对Contoller代码再稍做修改

public class User{    public bool VerifyPassword(string password, IEncryptionService encryptionService)    {        return this.Pasword == encryptionService.Encrypt(password);    }}public class UserController{    public void Logon(FormCollection form)    {        User user = _userRepository.GetByName(form.Get("LoginId"));        if (user == null)            throw new Exception("loginId", "账号不存在。");        if (user.VerifyPassword(form.Get("Password"), _encryptionService))            throw new Exception("password", "密码不正确。");        FormsAuthentication.SetAuthCookie(user.Name, createPersistentCookie);    }}

这样具体密码采用了什么加密接口就不用关心了，将此规则封闭在了domain内，还有一个主要目的是为了修改密码时能够复用。也许你不并认同这种做法，好像也没啥变化，当然也没关系，解决问题就行，我只想表达聚合可以封装哪些方法。
再仔细考虑我觉得上述代码表达的业务还是比较多，首先要查询该登录名的用户是否存在，再去验证密码，如果需求再有其他规则，如禁用的用户不能登录，再用具有时效性的用户过期了也不能登录等等，这样是不是越来越复杂，前端开发人员需要掌握的业务知识就会越来越多，所以最好将此业务封装在领域内，ui端只需要传入登录名和密码。
说了这么多，User本身是无法做到这一点的，那么还是要将这些业务规则写在上一篇提到过的DomainService

public class DomainService{    private readonly IUserRepository _userRepository;    private readonly IEncryptionService _encryptionService;    public DomainService(IUserRepository userRepository, IEncryptionService encryptionService)    {        this._userRepository = userRepository;        this._encryptionService = encryptionService;    }    public User Authenticate(string loginId, string password)    {        var user = _userRepository.GetByName(loginId);        if (user == null)            throw new Exception("loginId", "账号不存在。");        if (!user.VerifyPassword(password, _encryptionService))            throw new Exception("password", "密码不正确。");        return user;    }}public class UserController{    public void Logon(FormCollection form)    {        try {            User user = _domainService.Authenticate(form.Get("LoginId"), form.Get("Password"));            FormsAuthentication.SetAuthCookie(user.Name, createPersistentCookie);        }        catch (Exception) {            throw;        }    }}

这样是不是更好一点呢？
接下来再来说修改密码。直接上代码吧

public class User{    public void ChangePassword(string oldPwd, string newPwd, IEncryptionService encryptionService)    {        if (!this.VerifyPassword(oldPwd, encryptionService))            throw new Exception("旧密码输入不正确。");        this.Pasword = encryptionService.Encrypt(newPwd);    }}public class UserController{    public void ModifyPassword(FormCollection form)    {        try {            User user = _userRepository.GetByName(User.Identity.Name);            user.ChangePassword(form.Get("oldPwd"), form.Get("newPwd"), _encryptionService);            _userRepository.Update(user);        }        catch (Exception) {                        throw;        }    }}

好吧，这到这里吧，希望对你有帮助。下一篇再继续讨论丰富一下用户注册的过程，引入事件驱动。

 


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