原文见：http://raulraja.com/post/40997612883/sending-email-with-scala-and-akka-actors 作者正在学习Akka所以他决定使
原文见： http://raulraja.com/post/40997612883/sending-email-with-scala-and-akka-actors
作者正在学习Akka所以他决定使用Akka actor模型来写邮件发送服务，akka不光提供了扩展性和并行的框架，还有以下的好处：
- The builtin configurable supervisor strategy allows you to monitor child workers and decide what policy applies should there be an exception. 使用内置可配置的监控机制来监控子进程，并决定处理异常的策略
- I could easily reschedule email delivery attempts on common email exception often times thrown by SMTP servers. 在碰到SMTP服务异常等常见错误时，可以方便地重新调度邮件发送
- Actor routers allow you to dispatch messages to a pool of actors in an intelligent way. In this case we use the SmallestMailboxRouter which sends messages to actors in the pool with a smaller workload.使用Actor Router来智能分发信息到一个actor池。作者使用了SmallestMailboxRouter来发送信息到那些比较空闲的actor。
/* * Copyright (C) 2012 47 Degrees, LLC * http://47deg.com * [email protected] * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package servicesimport akka.actor._import play.api.libs.concurrent.Akkaimport play.api.Play.currentimport akka.actor.SupervisorStrategy._import scala.concurrent.duration._import akka.routing.SmallestMailboxRouterimport org.apache.commons.mail.{HtmlEmail, DefaultAuthenticator, EmailException}import akka.actor.ActorDSL._/** * Smtp config * @param tls if tls should be used with the smtp connections * @param ssl if ssl should be used with the smtp connections * @param port the smtp port * @param host the smtp host name * @param user the smtp user * @param password thw smtp password */case class SmtpConfig(tls : Boolean = false, ssl : Boolean = false, port : Int = 25, host : String, user : String, password: String)/** * The email message sent to Actors in charge of delivering email * * @param subject the email subject * @param recipient the recipient * @param from the sender * @param text alternative simple text * @param html html body */case class EmailMessage( subject: String, recipient: String, from: String, text: String, html: String, smtpConfig : SmtpConfig, retryOn: FiniteDuration, var deliveryAttempts: Int = 0)/** * Email service */object EmailService { /** * Uses the smallest inbox strategy to keep 20 instances alive ready to send out email * @see SmallestMailboxRouter */ val emailServiceActor = Akka.system.actorOf( Props[EmailServiceActor].withRouter( SmallestMailboxRouter(nrOfInstances = 50) ), name = "emailService" ) /** * public interface to send out emails that dispatch the message to the listening actors * @param emailMessage the email message */ def send(emailMessage: EmailMessage) { emailServiceActor ! emailMessage } /** * Private helper invoked by the actors that sends the email * @param emailMessage the email message */ private def sendEmailSync(emailMessage: EmailMessage) { // Create the email message val email = new HtmlEmail() email.setTLS(emailMessage.smtpConfig.tls) email.setSSL(emailMessage.smtpConfig.ssl) email.setSmtpPort(emailMessage.smtpConfig.port) email.setHostName(emailMessage.smtpConfig.host) email.setAuthenticator(new DefaultAuthenticator( emailMessage.smtpConfig.user, emailMessage.smtpConfig.password )) email.setHtmlMsg(emailMessage.html) .setTextMsg(emailMessage.text) .addTo(emailMessage.recipient) .setFrom(emailMessage.from) .setSubject(emailMessage.subject) .send() } /** * An Email sender actor that sends out email messages * Retries delivery up to 10 times every 5 minutes as long as it receives * an EmailException, gives up at any other type of exception */ class EmailServiceActor extends Actor with ActorLogging { /** * The actor supervisor strategy attempts to send email up to 10 times if there is a EmailException */ override val supervisorStrategy = OneForOneStrategy(maxNrOfRetries = 10) { case emailException: EmailException => { log.debug("Restarting after receiving EmailException : {}", emailException.getMessage) Restart } case unknownException: Exception => { log.debug("Giving up. Can you recover from this? : {}", unknownException) Stop } case unknownCase: Any => { log.debug("Giving up on unexpected case : {}", unknownCase) Stop } } /** * Forwards messages to child workers */ def receive = { case message: Any => context.actorOf(Props[EmailServiceWorker]) ! message } } /** * Email worker that delivers the message */ class EmailServiceWorker extends Actor with ActorLogging { /** * The email message in scope */ private var emailMessage: Option[EmailMessage] = None /** * Delivers a message */ def receive = { case email: EmailMessage => { emailMessage = Option(email) email.deliveryAttempts = email.deliveryAttempts + 1 log.debug("Atempting to deliver message") sendEmailSync(email) log.debug("Message delivered") } case unexpectedMessage: Any => { log.debug("Received unexepected message : {}", unexpectedMessage) throw new Exception("can't handle %s".format(unexpectedMessage)) } } /** * If this child has been restarted due to an exception attempt redelivery * based on the message configured delay */ override def preRestart(reason: Throwable, message: Option[Any]) { if (emailMessage.isDefined) { log.debug("Scheduling email message to be sent after attempts: {}", emailMessage.get) import context.dispatcher // Use this Actors' Dispatcher as ExecutionContext context.system.scheduler.scheduleOnce(emailMessage.get.retryOn, self, emailMessage.get) } } override def postStop() { if (emailMessage.isDefined) { log.debug("Stopped child email worker after attempts {}, {}", emailMessage.get.deliveryAttempts, self) } } }}
