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java發(fā)送郵件的方法網(wǎng)上有很多,但是大多是屬于阻塞式發(fā)送,spring 提供了很方便的實(shí)現(xiàn)多線程方法,結(jié)合spring可以快速實(shí)現(xiàn)異步發(fā)送郵件.

1. 引入依賴

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>
        <!-- 此外還需引入springboot 核心包-->

2. 配置spring連接池
   創(chuàng)建配置類,實(shí)現(xiàn)AsyncConfigurer

@Configuration
public class AsyncTaskConfig implements AsyncConfigurer {
    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        // 線程池維護(hù)線程的最少數(shù)量
        taskExecutor.setCorePoolSize(10);
        // 線程池維護(hù)線程的最大數(shù)量 
        taskExecutor.setMaxPoolSize(50);
        // 緩存隊(duì)列
        taskExecutor.setQueueCapacity(99999);
        // 對(duì)拒絕task的處理策略
        //(1) 默認(rèn)的ThreadPoolExecutor.AbortPolicy   處理程序遭到拒絕將拋出運(yùn)行時(shí)RejectedExecutionException;
        //(2) ThreadPoolExecutor.CallerRunsPolicy 線程調(diào)用運(yùn)行該任務(wù)的 execute 本身。此策略提供簡(jiǎn)單的反饋控制機(jī)制，能夠減緩新任務(wù)的提交速度
        //(3) ThreadPoolExecutor.DiscardPolicy  不能執(zhí)行的任務(wù)將被刪除;
        //(4) ThreadPoolExecutor.DiscardOldestPolicy  如果執(zhí)行程序尚未關(guān)閉，則位于工作隊(duì)列頭部的任務(wù)將被刪除，然后重試執(zhí)行程序（如果再次失敗，則重復(fù)此過(guò)程）
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        // 線程名前綴,方便排查問(wèn)題
        taskExecutor.setThreadNamePrefix("order-send-thread-");
        // 注意一定要初始化
        taskExecutor.initialize();

        return taskExecutor;

    }

    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return null;
    }
}

3. 創(chuàng)建發(fā)送郵件工具類
   此工具類出于本人的需要編寫,可根據(jù)實(shí)際需求改寫

public class EmailUtils {
    // 引入javaMailSender 
    private JavaMailSender mailSender;

    public EmailUtils(JavaMailSender mailSender) {
        this.mailSender = mailSender;
    }
    // 發(fā)送簡(jiǎn)單郵件 
    public void sendSimpleMail(String from, String to, String cc, String subject, String text) {
        if(StringUtils.isBlank(to)){
            return;
        }
        SimpleMailMessage message = new SimpleMailMessage();
        message.setFrom(from);
        message.setTo(to.split(","));
        if (StringUtils.isNotBlank(cc)) {
            message.setCc(cc.split(","));
        }
        message.setSubject(subject);
        message.setText(text);

        mailSender.send(message);
    }
    // 發(fā)送帶多個(gè)附件的郵件
    public void sendAttachmentMail(String from, String to, String cc, String subject, String text, List<Attachment> attachments) throws Exception {
        if(StringUtils.isBlank(to)){
            return;
        }
        MimeMessage mimeMessage = mailSender.createMimeMessage();

        MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, true);
        helper.setFrom(from);
        helper.setTo(to.split(","));
        if (StringUtils.isNotBlank(cc)) {
            helper.setCc(cc.split(","));
        }
        helper.setSubject(subject);
        helper.setText(text);
        for (Attachment attachment : attachments) {
            String attachmentName = attachment.attachmentName;
            DataSource attachmentFile = attachment.attachmentFile;
            helper.addAttachment(attachmentName, attachmentFile);
        }
        mailSender.send(mimeMessage);
    }
   // 發(fā)送帶單個(gè)附件的郵件
    public void sendAttachmentMail(String from, String to, String cc, String subject, String text, Attachment attachment) throws Exception {
        if (StringUtils.isBlank(to)) {
            return;
        }
        MimeMessage mimeMessage = mailSender.createMimeMessage();

        MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, true);
        helper.setFrom(from);
        helper.setTo(to.split(","));
        if (StringUtils.isNotBlank(cc)) {
            helper.setCc(cc.split(","));
        }

        helper.setSubject(subject);
        helper.setText(text);
        String attachmentName = attachment.attachmentName;
        DataSource attachmentFile = attachment.attachmentFile;
        helper.addAttachment(attachmentName, attachmentFile);

        mailSender.send(mimeMessage);
    }

    public static class Attachment {
        private String attachmentName;
        private DataSource attachmentFile;

        public Attachment(String attachmentName, DataSource attachmentFile) {
            this.attachmentName = attachmentName;
            this.attachmentFile = attachmentFile;
        }
    }
}

4. 創(chuàng)建發(fā)送郵件service

@Service
@Slf4j
@EnableAspectJAutoProxy(exposeProxy = true)
public class OrderSendService {
    @Autowired
    private JavaMailSender mailSender;

    @Async//注意此注解,有坑
    public void asyncSendEmail(String from, String to, String cc, String subject, String text, List<OrderExcelEntity> orderList) throws Exception {
        EmailUtils emailUtils = new EmailUtils(mailSender);
        DataSource excelDataSource = generateExcelDataSource(orderList);
        EmailUtils.Attachment attachment = new EmailUtils.Attachment("XXX.xls", excelDataSource);
        emailUtils.sendAttachmentMail(from, to, cc, subject, text, attachment);
    }
}

springboot 實(shí)現(xiàn)發(fā)送郵件的核心方法已完成,引用時(shí)最好根據(jù)本人實(shí)際需要進(jìn)行改寫.
需要注意的是,當(dāng)本類中非異步方法調(diào)用asyncSendEmail()時(shí),怎么也不能實(shí)現(xiàn)異步,比方說(shuō)我需要定時(shí)調(diào)用此異步發(fā)送郵件方法

    @Scheduled(cron = "0 1 0/1 * * ?  ")
    public void sendMailTimer() {
        ((OrderSendService) AopContext.currentProxy()).asyncSendEmail(from, to, cc,subject,text,orderList);
    }

填坑方法:
1.在類上增加 @EnableAspectJAutoProxy(exposeProxy = true) 注解

2.調(diào)用時(shí)增加 ((OrderSendService) AopContext.currentProxy())

自此springboot 實(shí)現(xiàn)異步發(fā)送郵件方法已完成,有不對(duì)之處,歡迎指正