Chemmy's Blog

如何开始DDD(续) - young.han - 博客园

Excerpt

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，如地址，邮编

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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，表示认同，所以今天一并修改了一下。

<span>public</span> <span>class</span><span> AddressInfo
{
    </span><span>public</span> AddressInfo(<span>string</span> province, <span>string</span> city, <span>string</span> address, <span>string</span><span> postcode)
    {
        </span><span>this</span>.Province =<span> province;
        </span><span>this</span>.City =<span> city;
        </span><span>this</span>.Address =<span> address;
        </span><span>this</span>.Postcode =<span> postcode;
    }

    </span><span>public</span> <span>string</span> Province { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> City { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> Address { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> Postcode { <span>get</span>; <span>private</span> <span>set</span><span>; }
}

</span><span>public</span> <span>class</span><span> User
{
    </span><span>public</span> User(<span>string</span> name, <span>string</span> password, <span>string</span><span> email)
    {
        </span><span>this</span>.Name =<span> name;
        </span><span>this</span>.Password =<span> password;
        </span><span>this</span>.Email =<span> email;
    }

    </span><span>public</span> <span>string</span> Id { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> Name { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> Password { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> RealName { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> Email { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> Cellphone { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> <span>string</span> Birthday { <span>get</span>; <span>private</span> <span>set</span><span>; }
    </span><span>public</span> AddressInfo Address { <span>get</span>; <span>private</span> <span>set</span><span>; }

    </span><span>public</span> <span>void</span> UpdateBasicInfo(<span>string</span> realName, <span>string</span> birthday, <span>string</span><span> cellphone)
    {
        </span><span>this</span>.RealName =<span> realName;
        </span><span>this</span>.Birthday =<span> birthday;
        </span><span>this</span>.Cellphone =<span> cellphone;
    }

    </span><span>public</span> <span>void</span><span> UpdateAddress(AddressInfo address)
    {
        </span><span>this</span>.Address =<span> address;
    }
}</span>

那么前端的代码也很简单

<span>public</span> <span>class</span><span> UserController
{
    </span><span>private</span> <span>readonly</span><span> IUserRepository _userRepository;
    </span><span>public</span> <span>void</span><span> SetProfile(FormCollection form)
    {
        </span><span>var</span> user = _userRepository.Get(form.Get(<span>"</span><span>id</span><span>"</span><span>));

        user.UpdateBasicInfo(form.Get(</span><span>"</span><span>name</span><span>"</span>), form.Get(<span>"</span><span>birthday</span><span>"</span>), form.Get(<span>"</span><span>cellphone</span><span>"</span><span>));
    }

    </span><span>public</span> <span>void</span><span> SetAddress(FormCollection form)
    {
        </span><span>var</span> user = _userRepository.Get(form.Get(<span>"</span><span>id</span><span>"</span><span>));

        </span><span>var</span> address = <span>new</span> AddressInfo(form.Get(<span>"</span><span>province</span><span>"</span>), form.Get(<span>"</span><span>city</span><span>"</span><span>), 
            form.Get(</span><span>"</span><span>address</span><span>"</span>), form.Get(<span>"</span><span>postcode</span><span>"</span><span>));

        user.UpdateAddress(address);
    }
}</span>

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：

<span>public</span> <span>interface</span><span> IUserRepository
{
    User GetByName(</span><span>string</span><span> loginId);
}

</span><span>public</span> <span>class</span><span> UserController
{
    </span><span>private</span> <span>readonly</span><span> IUserRepository _userRepository;
    </span><span>public</span><span> UserController(IUserRepository userRepository)
    {
        </span><span>this</span>._userRepository =<span> userRepository;
    }

    </span><span>public</span> <span>void</span><span> Logon(FormCollection form)
    {
        User user </span>= _userRepository.GetByName(form.Get(<span>"</span><span>LoginId</span><span>"</span><span>));
        </span><span>if</span> (user == <span>null</span><span>)
            </span><span>throw</span> <span>new</span> Exception(<span>"</span><span>loginId</span><span>"</span>, <span>"</span><span>账号不存在。</span><span>"</span><span>);
        </span><span>if</span> (user.Password != form.Get(<span>"</span><span>Password</span><span>"</span><span>))
            </span><span>throw</span> <span>new</span> Exception(<span>"</span><span>password</span><span>"</span>, <span>"</span><span>密码不正确。</span><span>"</span><span>);

        FormsAuthentication.SetAuthCookie(user.Name, createPersistentCookie);
    }
}</span>

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

<span>if</span> (user.Password != _encryptionService.Encrypt(form.Get(<span>"</span><span>Password</span><span>"</span>)))

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

<span>public</span> <span>class</span><span> User
{
    </span><span>public</span> <span>bool</span> VerifyPassword(<span>string</span><span> password, IEncryptionService encryptionService)
    {
        </span><span>return</span> <span>this</span>.Pasword ==<span> encryptionService.Encrypt(password);
    }
}

</span><span>public</span> <span>class</span><span> UserController
{
    </span><span>public</span> <span>void</span><span> Logon(FormCollection form)
    {
        User user </span>= _userRepository.GetByName(form.Get(<span>"</span><span>LoginId</span><span>"</span><span>));
        </span><span>if</span> (user == <span>null</span><span>)
            </span><span>throw</span> <span>new</span> Exception(<span>"</span><span>loginId</span><span>"</span>, <span>"</span><span>账号不存在。</span><span>"</span><span>);
        </span><span>if</span> (user.VerifyPassword(form.Get(<span>"</span><span>Password</span><span>"</span><span>), _encryptionService))
            </span><span>throw</span> <span>new</span> Exception(<span>"</span><span>password</span><span>"</span>, <span>"</span><span>密码不正确。</span><span>"</span><span>);

        FormsAuthentication.SetAuthCookie(user.Name, createPersistentCookie);
    }
}</span>

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。也许你并不认同这种做法，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，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

<span>public</span> <span>class</span><span> DomainService
{
    </span><span>private</span> <span>readonly</span><span> IUserRepository _userRepository;
    </span><span>private</span> <span>readonly</span><span> IEncryptionService _encryptionService;
    </span><span>public</span><span> DomainService(IUserRepository userRepository, IEncryptionService encryptionService)
    {
        </span><span>this</span>._userRepository =<span> userRepository;
        </span><span>this</span>._encryptionService =<span> encryptionService;
    }

    </span><span>public</span> User Authenticate(<span>string</span> loginId, <span>string</span><span> password)
    {
        </span><span>var</span> user =<span> _userRepository.GetByName(loginId);
        </span><span>if</span> (user == <span>null</span><span>)
            </span><span>throw</span> <span>new</span> Exception(<span>"</span><span>loginId</span><span>"</span>, <span>"</span><span>账号不存在。</span><span>"</span><span>);
        </span><span>if</span> (!<span>user.VerifyPassword(password, _encryptionService))
            </span><span>throw</span> <span>new</span> Exception(<span>"</span><span>password</span><span>"</span>, <span>"</span><span>密码不正确。</span><span>"</span><span>);

        </span><span>return</span><span> user;
    }
}

</span><span>public</span> <span>class</span><span> UserController
{
    </span><span>public</span> <span>void</span><span> Logon(FormCollection form)
    {
        </span><span>try</span><span> {
            User user </span>= _domainService.Authenticate(form.Get(<span>"</span><span>LoginId</span><span>"</span>), form.Get(<span>"</span><span>Password</span><span>"</span><span>));
            FormsAuthentication.SetAuthCookie(user.Name, createPersistentCookie);
        }
        </span><span>catch</span><span> (Exception) {
            </span><span>throw</span><span>;
        }
    }
}</span>

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

<span>public</span> <span>class</span><span> User
{
    </span><span>public</span> <span>void</span> ChangePassword(<span>string</span> oldPwd, <span>string</span><span> newPwd, IEncryptionService encryptionService)
    {
        </span><span>if</span> (!<span>this</span><span>.VerifyPassword(oldPwd, encryptionService))
            </span><span>throw</span> <span>new</span> Exception(<span>"</span><span>旧密码输入不正确。</span><span>"</span><span>);

        </span><span>this</span>.Pasword =<span> encryptionService.Encrypt(newPwd);
    }
}

</span><span>public</span> <span>class</span><span> UserController
{
    </span><span>public</span> <span>void</span><span> ModifyPassword(FormCollection form)
    {
        </span><span>try</span><span> {
            User user </span>=<span> _userRepository.GetByName(User.Identity.Name);
            user.ChangePassword(form.Get(</span><span>"</span><span>oldPwd</span><span>"</span>), form.Get(<span>"</span><span>newPwd</span><span>"</span><span>), _encryptionService);
            _userRepository.Update(user);
        }
        </span><span>catch</span><span> (Exception) {
            
            </span><span>throw</span><span>;
        }
    }
}</span>

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。