1. 简介

Spring Boot 收发邮件最简便方式是通过 spring-boot-starter-mail。

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-mail</artifactId>
</dependency>

spring-boot-starter-mail 本质上是使用 JavaMail(javax.mail)。如果想对 JavaMail 有进一步了解，可以参考： JavaMail 使用指南

2. API

Spring Framework 提供了一个使用 JavaMailSender 接口发送电子邮件的简单抽象，这是发送邮件的核心 API。

3. 配置

Spring Boot 为 JavaMailSender 提供了自动配置以及启动器模块。
如果 spring.mail.host 和相关库（由 spring-boot-starter-mail 定义）可用，则 Spring Boot 会创建默认 JavaMailSender（如果不存在）。可以通过 spring.mail 命名空间中的配置项进一步自定义发件人。 特别是，某些默认超时值是无限的，您可能希望更改它以避免线程被无响应的邮件服务器阻塞，如以下示例所示：

spring.mail.properties.mail.smtp.connectiontimeout=5000
spring.mail.properties.mail.smtp.timeout=3000
spring.mail.properties.mail.smtp.writetimeout=5000

也可以使用 JNDI 中的现有会话配置 JavaMailSender：
spring.mail.jndi-name=mail/Session
以下为 Spring Boot 关于 Mail 的配置：
有关更多详细信息，请参阅 MailProperties。

# Email (MailProperties)
spring.mail.default-encoding=UTF-8 # Default MimeMessage encoding.
spring.mail.host= # SMTP server host. For instance, `smtp.example.com`.
spring.mail.jndi-name= # Session JNDI name. When set, takes precedence over other Session settings.
spring.mail.password= # Login password of the SMTP server.
spring.mail.port= # SMTP server port.
spring.mail.properties.*= # Additional JavaMail Session properties.
spring.mail.protocol=smtp # Protocol used by the SMTP server.
spring.mail.test-connection=false # Whether to test that the mail server is available on startup.
spring.mail.username= # Login user of the SMTP server.

4. 实战

4.1. 引入依赖

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-mail</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency><dependency><groupId>com.github.dozermapper</groupId><artifactId>dozer-spring-boot-starter</artifactId><version>6.4.0</version></dependency>
</dependencies>

4.2. 配置邮件属性

在 src/main/resources 目录下添加 application-163.properties 配置文件，内容如下：

spring.mail.host = smtp.163.com
spring.mail.username = xxxxxx
spring.mail.password = xxxxxx
spring.mail.properties.mail.smtp.auth = true
spring.mail.properties.mail.smtp.starttls.enable = true
spring.mail.properties.mail.smtp.starttls.required = true
spring.mail.default-encoding = UTF-8mail.domain = 163.com
mail.from = ${spring.mail.username}@${mail.domain}

注：需替换有效的 spring.mail.username、spring.mail.password。
application-163.properties 配置文件表示使用 163 邮箱时的配置，为了使之生效，需要通过 spring.profiles.active = 163 来激活它。
在 src/main/resources 目录下添加 application.properties 配置文件，内容如下：
spring.profiles.active = 163

4.3. Java 代码

首先，需要读取部分配置属性，方法如下：

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
import org.springframework.validation.annotation.Validated;@Validated
@Component
@ConfigurationProperties(prefix = "mail")
public class MailProperties {private String domain;private String from;public String getDomain() {return domain;}public void setDomain(String domain) {this.domain = domain;}public String getFrom() {return from;}public void setFrom(String from) {this.from = from;}
}

接着，定义一个邮件参数实体类（使用 lombok 简化了 getter、setter）：

import lombok.Data;
import java.util.Date;@Data
public class MailDTO {private String from;private String replyTo;private String[] to;private String[] cc;private String[] bcc;private Date sentDate;private String subject;private String text;private String[] filenames;
}

接着，实现发送邮件的功能接口：

import com.github.dozermapper.core.Mapper;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.mail.SimpleMailMessage;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.stereotype.Service;import javax.mail.MessagingException;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import java.io.IOException;@Service
public class MailService {private final Logger log = LoggerFactory.getLogger(this.getClass());@Autowiredprivate MailProperties mailProperties;@Autowiredprivate JavaMailSender javaMailSender;@Autowiredprivate Mapper mapper;public void sendSimpleMailMessage(MailDTO mailDTO) {SimpleMailMessage simpleMailMessage = mapper.map(mailDTO, SimpleMailMessage.class);if (StringUtils.isEmpty(mailDTO.getFrom())) {mailDTO.setFrom(mailProperties.getFrom());}javaMailSender.send(simpleMailMessage);}public void sendMimeMessage(MailDTO mailDTO) {MimeMessage mimeMessage = javaMailSender.createMimeMessage();MimeMessageHelper messageHelper;try {messageHelper = new MimeMessageHelper(mimeMessage, true);if (StringUtils.isEmpty(mailDTO.getFrom())) {messageHelper.setFrom(mailProperties.getFrom());}messageHelper.setTo(mailDTO.getTo());messageHelper.setSubject(mailDTO.getSubject());mimeMessage = messageHelper.getMimeMessage();MimeBodyPart mimeBodyPart = new MimeBodyPart();mimeBodyPart.setContent(mailDTO.getText(), "text/html;charset=UTF-8");// 描述数据关系MimeMultipart mm = new MimeMultipart();mm.setSubType("related");mm.addBodyPart(mimeBodyPart);// 添加邮件附件for (String filename : mailDTO.getFilenames()) {MimeBodyPart attachPart = new MimeBodyPart();try {attachPart.attachFile(filename);} catch (IOException e) {e.printStackTrace();}mm.addBodyPart(attachPart);}mimeMessage.setContent(mm);mimeMessage.saveChanges();} catch (MessagingException e) {e.printStackTrace();}javaMailSender.send(mimeMessage);}
}