1. 前言

最近pm臨時提出了多種郵件驗證操作的需求，因為一時間也沒有找到好的郵件收發元件，也抱著研究ABP的心態，就花了幾小時時間探究了一下ABP中關於Email的處理和操作。其實郵件操作大多大同小異，這次只是希望介紹一下ABP中實現功能的程式碼結構而已，以下是具體過程

演示的ABP程式碼版本為0.9.0.0，不過後面版本對於這部分的修改較少，所以完全不影響之後版本的移植使用

2. 實現過程

ABP的Mail操作放在了Abp.Net.Mail和Abp.Net.Mail.Smtp中，第一步先讓我們直接看看這個資料夾下類及介面的程式碼圖（未經允許不可使用）

1. 程式碼圖（重）

根據程式碼圖可以發現ABP對於Mail處理主要由三部分組成

• 第一部分是通過繼承SettingProvider的EmailSettingProvider來對Mail相關引數進行設定（其中EmailSettingNames定義相關字串）
• 第二部分是以IEmailSenderConfiguration介面為基派生出的對SettingProvider設定的郵件引數進行讀取和傳輸的相關操作類
• 第三部分是以IEmailSender介面為基派生出的Mail傳送操作相關類

至於Smtp開頭的檔案，則是以Smtp形式進行郵件傳送的一種實現檔案而已，後文也將直接使用該種方式進行處理

2.具體實現

在具體的實現上，我發現ABP本身的Mail相關類已經十分完整，只是在郵件引數的配置上需要採取自定義的實現，所以我直接抽取了ABP的原始碼來進行演示

2.1 定義AppSettingNames及AppSettingProvider

AppSettingNames中定義相關的唯一字串，大家可以認為是Key，而AppSettingProvider中則是將Key對應的郵件引數賦值，供之後的Configuration讀取

郵件功能推薦放在Core模組中，完成相關的provider後在CoreModule加入Configuration.Settings.Providers.Add<AppSettingProvider>();

即可生效

public static class AppSettings
{
    /// <summary>
    /// SMTP related email settings.
    /// </summary>
    public static class Smtp
    {
        /// <summary>
        /// Abp.Net.Mail.DefaultFromAddress
        /// </summary>
        public const string DefaultAddress = "Trucking.Net.Mail.DefaultFromAddress";

        /// <summary>
        /// Abp.Net.Mail.DefaultFromDisplayName
        /// </summary>
        public const string DefaultDisplayName = "Trucking.Net.Mail.DefaultFromDisplayName";

        /// <summary>
        /// Abp.Net.Mail.Smtp.Host
        /// </summary>
        public const string Host = "Trucking.Net.Mail.Smtp.Host";

        /// <summary>
        /// Abp.Net.Mail.Smtp.Port
        /// </summary>
        public const string Port = "Trucking.Net.Mail.Smtp.Port";

        /// <summary>
        /// Abp.Net.Mail.Smtp.UserName
        /// </summary>
        public const string UserName = "Trucking.Net.Mail.Smtp.UserName";

        /// <summary>
        /// Abp.Net.Mail.Smtp.Password
        /// </summary>
        public const string Password = "Trucking.Net.Mail.Smtp.Password";

        /// <summary>
        /// Abp.Net.Mail.Smtp.Domain
        /// </summary>
        public const string Domain = "Trucking.Net.Mail.Smtp.Domain";

        /// <summary>
        /// Abp.Net.Mail.Smtp.EnableSsl
        /// </summary>
        public const string EnableSsl = "Trucking.Net.Mail.Smtp.EnableSsl";

        /// <summary>
        /// Abp.Net.Mail.Smtp.UseDefaultCredentials
        /// </summary>
        public const string UseDefaultCredentials = "Trucking.Net.Mail.Smtp.UseDefaultCredentials";
    }
}

public class AppSettingProvider : SettingProvider
{
    public override IEnumerable<SettingDefinition> GetSettingDefinitions(SettingDefinitionProviderContext context)
    {
        return new[]
        {
            new SettingDefinition(AppSettings.Smtp.Host, "smtp.gmail.com", L("SmtpHost"),
                scopes: SettingScopes.Application | SettingScopes.Tenant),
            new SettingDefinition(AppSettings.Smtp.Port, "587", L("SmtpPort"),
                scopes: SettingScopes.Application | SettingScopes.Tenant),
            new SettingDefinition(AppSettings.Smtp.UserName, "[email protected]", L("Username"),
                scopes: SettingScopes.Application | SettingScopes.Tenant),
            new SettingDefinition(AppSettings.Smtp.Password, "mypassword", L("Password"),
                scopes: SettingScopes.Application | SettingScopes.Tenant),
            new SettingDefinition(AppSettings.Smtp.Domain, "", L("DomainName"),
                scopes: SettingScopes.Application | SettingScopes.Tenant),
            new SettingDefinition(AppSettings.Smtp.EnableSsl, "true", L("UseSSL"),
                scopes: SettingScopes.Application | SettingScopes.Tenant),
            new SettingDefinition(AppSettings.Smtp.UseDefaultCredentials, "false", L("UseDefaultCredentials"),
                scopes: SettingScopes.Application | SettingScopes.Tenant),
            new SettingDefinition(AppSettings.Smtp.DefaultAddress, "[email protected]",
                L("DefaultEmailAddress"), scopes: SettingScopes.Application | SettingScopes.Tenant),
            new SettingDefinition(AppSettings.Smtp.DefaultDisplayName, "CompanyName",
                L("DefaultDisplayName"), scopes: SettingScopes.Application | SettingScopes.Tenant)
        };
    }

    private static LocalizableString L(string name)
    {
        return new LocalizableString(name, AbpConsts.LocalizationSourceName);
    }
}

2.2 EmailSenderConfiguration配置

這個類的作用如上面提到的那樣，主要是讀取自定義的AppSettingProvider中設定的郵件引數值

IUserEmailSenderConfiguration介面略

public class UserEmailSenderConfiguration : TruckingServiceBase, IUserEmailSenderConfiguration, ITransientDependency
{
    /// <summary>
    /// Gets a setting value by checking. Throws <see cref="AbpException"/> if it's null or empty.
    /// </summary>
    /// <param name="name">Name of the setting</param>
    /// <returns>Value of the setting</returns>
    protected string GetNotEmptySettingValue(string name)
    {
        var value = SettingManager.GetSettingValue(name);
        if (value.IsNullOrEmpty())
        {
            throw new AbpException(String.Format("Setting value for '{0}' is null or empty!", name));
        }

        return value;
    }

    /// <summary>
    /// SMTP Host name/IP.
    /// </summary>
    public string Host
    {
        get { return GetNotEmptySettingValue(AppSettings.Smtp.Host); }
    }

    /// <summary>
    /// SMTP Port.
    /// </summary>
    public int Port
    {
        get { return SettingManager.GetSettingValue<int>(AppSettings.Smtp.Port); }
    }

    /// <summary>
    /// User name to login to SMTP server.
    /// </summary>
    public string UserName
    {
        get { return GetNotEmptySettingValue(AppSettings.Smtp.UserName); }
    }

    /// <summary>
    /// Password to login to SMTP server.
    /// </summary>
    public string Password
    {
        get { return GetNotEmptySettingValue(AppSettings.Smtp.Password); }
    }

    /// <summary>
    /// Domain name to login to SMTP server.
    /// </summary>
    public string Domain
    {
        get { return SettingManager.GetSettingValue(AppSettings.Smtp.Domain); }
    }

    /// <summary>
    /// Is SSL enabled?
    /// </summary>
    public bool EnableSsl
    {
        get { return SettingManager.GetSettingValue<bool>(AppSettings.Smtp.EnableSsl); }
    }

    /// <summary>
    /// Use default credentials?
    /// </summary>
    public bool UseDefaultCredentials
    {
        get { return SettingManager.GetSettingValue<bool>(AppSettings.Smtp.UseDefaultCredentials); }
    }

    public string DefaultAddress
    {
        get { return GetNotEmptySettingValue(AppSettings.Smtp.DefaultAddress); }
    }

    public string DefaultDisplayName
    {
        get { return SettingManager.GetSettingValue(AppSettings.Smtp.DefaultDisplayName); }
    }
}

2.3 SmtpEmailSender實現（Smtp實現郵件傳送）

UserSmtpEmailSender類才是真正的對Mail操作類，它通過注入IUserEmailSenderConfiguration介面，讀取相關的Mail引數，如Host，UserName，Password等，然後再呼叫.NET的Mail傳送郵件。

IUserSmtpEmailSender介面略

public class UserSmtpEmailSender : IUserSmtpEmailSender, ITransientDependency
{
    private readonly IUserEmailSenderConfiguration _configuration;

    public UserSmtpEmailSender(IUserEmailSenderConfiguration configuration)
    {
        _configuration = configuration;
    }
    
    public async Task SendAsync(string to, string subject, string body, bool isBodyHtml = true)
    {
        await SendAsync(_configuration.DefaultAddress, to, subject, body, isBodyHtml);
    }

    public void Send(string to, string subject, string body, bool isBodyHtml = true)
    {
        Send(_configuration.DefaultAddress, to, subject, body, isBodyHtml);
    }

    public async Task SendAsync(string from, string to, string subject, string body, bool isBodyHtml = true)
    {
        await SendAsync(new MailMessage(from, to, subject, body) {IsBodyHtml = isBodyHtml});
    }

    public void Send(string from, string to, string subject, string body, bool isBodyHtml = true)
    {
        Send(new MailMessage(from, to, subject, body) {IsBodyHtml = isBodyHtml});
    }

    public async Task SendAsync(MailMessage mail, bool normalize = true)
    {
        if (normalize)
            NormalizeMail(mail);

        await SendEmailAsync(mail);
    }

    public void Send(MailMessage mail, bool normalize = true)
    {
        if (normalize)
            NormalizeMail(mail);

        SendEmail(mail);
    }

    public SmtpClient BuildClient()
    {
        var host = _configuration.Host;
        var port = _configuration.Port;

        var smtpClient = new SmtpClient(host, port);
        try
        {
            if (_configuration.EnableSsl)
                smtpClient.EnableSsl = true;

            if (_configuration.UseDefaultCredentials)
            {
                smtpClient.UseDefaultCredentials = true;
            }
            else
            {
                smtpClient.UseDefaultCredentials = false;

                var userName = _configuration.UserName;
                if (!userName.IsNullOrEmpty())
                {
                    var password = _configuration.Password;
                    var domain = _configuration.Domain;
                    smtpClient.Credentials = !domain.IsNullOrEmpty()
                        ? new NetworkCredential(userName, password, domain)
                        : new NetworkCredential(userName, password);
            }
        }
        
        return smtpClient;
    }
    catch
    {
            smtpClient.Dispose();
            throw;
        }
    }

    /// <summary>
    ///     Normalizes given email.
    ///     Fills <see cref="MailMessage.From" /> if it's not filled before.
    ///     Sets encodings to UTF8 if they are not set before.
    /// </summary>
    /// <param name="mail">Mail to be normalized</param>
    protected virtual void NormalizeMail(MailMessage mail)
    {
        if ((mail.From == null) || mail.From.Address.IsNullOrEmpty())
            mail.From = new MailAddress(
                _configuration.DefaultAddress,
                _configuration.DefaultDisplayName,
                Encoding.UTF8
            );

        if (mail.HeadersEncoding == null)
            mail.HeadersEncoding = Encoding.UTF8;

        if (mail.SubjectEncoding == null)
            mail.SubjectEncoding = Encoding.UTF8;

        if (mail.BodyEncoding == null)
            mail.BodyEncoding = Encoding.UTF8;
    }

    protected async Task SendEmailAsync(MailMessage mail)
    {
        using (var smtpClient = BuildClient())
        {
            await smtpClient.SendMailAsync(mail);
        }
    }

    protected void SendEmail(MailMessage mail)
    {
        using (var smtpClient = BuildClient())
        {
            smtpClient.Send(mail);
        }
    }
}

之後我們只需要再呼叫該EmailSender的SendAsync，填入對應的引數，親測有效。如果之後要更換郵件元件，則只需要實現對應的UserLibraryEmailSerder即可。

至此，我們便將ABP中單獨的一個郵件功能抽離了出來並做了相關解釋，其實只要花點功夫，自己手動剝離程式碼圖也可以理解了。至於一個簡單的郵件功能為什麼在ABP中要實現得如此複雜，每個程式設計師有每個程式設計師的答案，還是繼續學習吧