SpringBoot 动态配置邮箱发件人过程解析

前言

现在的消息模块少不了邮件发送、短信发送和手机推送的功能。邮件发送的功能历史最为悠久，也算的上烂大街的功能。一般在配置文件中设置好邮箱地址、账号、密码和发件服务器地址后便不会再去改动。可是有的客户却希望人为指定发件人信息。这个需求并不过分，需要解决两个大问题：如何在容器启动成功后重新修改发送邮件的bean。如何在服务器重启后，发件人依然是更改后的配置信息。这里记录实现的步骤。

需求分析

一）、在未配置邮箱账号时，系统拥有默认的邮箱发件人

二）、重新设置邮箱发件人后，需立即生效

三）、重启服务器后，邮箱发件人依然是更改后的邮箱账号，而非默认发件人

基础的邮箱发送

邮箱发送的功能放在现在变得非常的简单好用，一导二配三发送。????

第一步：导入邮箱依赖包

compile('org.springframework.boot:spring-boot-starter-mail')

第二步：配置发件人邮箱信息

spring:
  mail:
   host: smtp.mxhichina.com
   username: itdragon@xx
   password: itdragon
   default-encoding: utf-8

第三步：发送邮件

@autowired
lateinit var javamailsender: javamailsender
fun pushmsgemail(target: string, subject: string, content: string) {
  if (target.isempty() || !pattern.matches(reg_email_format, target)) return
  val mailmsg = simplemailmessage()
  mailmsg.setfrom(mailusername!!)
  mailmsg.setto(target)
  mailmsg.setsubject(subject)
  mailmsg.settext(content)
  javamailsender.send(mailmsg)
}

可配置的邮件发送

这里的可配置值的是配置邮箱的发件人。首先我们要解决第一个问题，javamailsender 的bean对象是在容器启动成功后就已经注入到容器中。如何在容器启动后重新注入新的javamailsender 的bean对象呢？

网上找了一些案例，他们都是通过销毁bean然后再重新创建bean的方式实现。我有点好奇地是，为什么不直接将新的对象直接赋值从而替换原有的bean对象？spring默认是单例模式，从java内存的角度看，这样做似乎没毛病！如果有不对的地方望不吝赐教????

@autowired
lateinit var javamailsender: javamailsender
fun configemail(postmailconfig: postmailconfig): javamailsender {
  val javamailsender = javamailsenderimpl()
  javamailsender.host = postmailconfig.mailhost
  javamailsender.username = postmailconfig.mailusername
  javamailsender.password = postmailconfig.mailpassword
  val javamailproperties = properties()
  javamailproperties["mail.smtp.auth"] = true
  javamailproperties["mail.smtp.starttls.enable"] = true
  javamailproperties["mail.smtp.timeout"] = 5000
  javamailproperties["mail.smtp.socketfactory.class"] = "javax.net.ssl.sslsocketfactory"
  javamailproperties["mail.smtp.socketfactory.port"] = "465"
  javamailproperties["mail.smtp.port"] = "465"
  javamailsender.javamailproperties = javamailproperties
  this.javamailsender = javamailsender
  return javamailsender
}

再来解决第二个问题，服务器重启后，默认情况下依然会重新加载application.yml中的配置信息。这会出现邮箱发件人和实际配置的发件人不匹配的情况。其实这个问题也很好解决，加一个事件监听器，在容器初始化成功后执行，根据之前保存的邮箱信息，重新配置邮箱。当然，我们需要一张表记录当前发件人信息。

// 创建事件监听器
class applicationstartup : applicationlistener<contextrefreshedevent> {  
  override fun onapplicationevent(contextrefreshedevent: contextrefreshedevent) {
    val systembaseconfigmapper = contextrefreshedevent.applicationcontext.getbean(systembaseconfigmapper::class.java)
    val postmailconfig = systembaseconfigmapper.selectbymail()
    val mailservice = contextrefreshedevent.applicationcontext.getbean(mailservice::class.java)
    mailservice.configemail(postmailconfig)
  }
  
}
// 注册事件监听器
fun main(args: array<string>) {
  
  val springapplication = springapplication(startapplication::class.java)
  springapplication.addlisteners(applicationstartup())
  springapplication.run(*args)  
}

最后发送邮件的代码如下

@service
class mailserviceimpl : mailservice {
  @value("\${spring.mail.username}")
  var mailusername: string? = null
  @autowired
  lateinit var javamailsender: javamailsender
  @autowired
  lateinit var systembaseconfigmapper: systembaseconfigmapper
  override fun pushmsgemail(target: string, subject: string, content: string) {
    if (target.isempty() || !pattern.matches(reg_email_format, target)) return
    val mailmsg = simplemailmessage()
    mailmsg.setfrom(mailusername!!)
    mailmsg.setto(target)
    mailmsg.setsubject(subject)
    mailmsg.settext(content)
    try {
      systembaseconfigmapper.selectbymailname()?.let {
        mailmsg.setfrom(it.value!!)
      }
      javamailsender.send(mailmsg)
    } catch (e: exception) {
      e.printstacktrace()
    }
  }

  override fun configemail(postmailconfig: postmailconfig): javamailsender {
    val javamailsender = javamailsenderimpl()
    javamailsender.host = postmailconfig.mailhost
    javamailsender.username = postmailconfig.mailusername
    javamailsender.password = postmailconfig.mailpassword
    val javamailproperties = properties()
    javamailproperties["mail.smtp.auth"] = true
    javamailproperties["mail.smtp.starttls.enable"] = true
    javamailproperties["mail.smtp.timeout"] = 5000
    javamailproperties["mail.smtp.socketfactory.class"] = "javax.net.ssl.sslsocketfactory"
    javamailproperties["mail.smtp.socketfactory.port"] = "465"
    javamailproperties["mail.smtp.port"] = "465"
    javamailsender.javamailproperties = javamailproperties
    this.javamailsender = javamailsender
    return javamailsender
  }
}

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