使用SpringBoot发邮件

SpringBoot中已有发邮件的工具包，只需要引用即可使用

1，pom引用

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

2，在配置文件中配置邮件服务器信息。这里需要一个可用的邮件服务器。

spring.mail.default-encoding=utf-8
spring.mail.host=mail.xxxx.com
spring.mail.username=xxxx@xxxx.com
spring.mail.password=password

3，编写发邮件service，调用JavaMailSender.send()即可，支持简单文本邮件、富文本邮件、html邮件

Service代码如下

 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.core.io.FileSystemResource;
 import org.springframework.mail.MailException;
 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.MimeMessage;
 import java.io.File;

 @Service
 public class EmailService {
     @Autowired
     private JavaMailSender mailSender;

     @Value("${spring.mail.username}")
     private String from;

     /**
      * 发送简单文本邮件
      * @param content 邮件正文
      * @param subject 邮件主题
      * @param to 邮件接收地址
      * */
     public void sendSimpleMail(String to, String subject, String content) throws MailException {
         System.out.println("-----from:" + from);
         System.out.println("-----to:" + to);
         System.out.println("-----subject:" + subject);
         System.out.println("-----content:" + content);

         SimpleMailMessage message = new SimpleMailMessage();
         message.setFrom(from);
         message.setTo(to);
         message.setSubject(subject);
         message.setText(content);
         mailSender.send(message);
     }

     /**
      * 发送富文本邮件
      * @param content 邮件正文
      * @param rscId 设置在header头中的文件ID
      * @param rscPath 图片路径
      * @param subject 邮件主题
      * @param to 邮件接收地址
      * */
     public void sendRichTextMail(String to, String subject, String content, String rscPath, String rscId) throws MessagingException {
         //MimeMessageHelper支持发送复杂邮件模板，支持文本、附件、HTML、图片等。
         //如果需要发送多张图片，可以改变传参方式，使用集合添加多个<img src='cid:rscId'>和helper.addInline(rscId, res);即可实现

         MimeMessage message = mailSender.createMimeMessage();
         MimeMessageHelper helper = new MimeMessageHelper(message, true);
         helper.setFrom(from);
         helper.setTo(to);
         helper.setSubject(subject);
         helper.setText(content, true);
         File file = new File(rscPath);
         FileSystemResource res = new FileSystemResource(file);
         helper.addInline(rscId, res);

         mailSender.send(message);

     }

     /**
      * 发送HTML邮件
      * @param to 邮件接收地址
      * @param subject 邮件主题
      * @param content 邮件正文
      * */
     public void sendHtmlMail(String to, String subject, String content) throws MessagingException {
         MimeMessage message = mailSender.createMimeMessage();
         //true 表⽰示需要创建⼀一个 multipart message
         MimeMessageHelper helper = new MimeMessageHelper(message, true);
         helper.setFrom(from);
         helper.setTo(to);
         helper.setSubject(subject);
         helper.setText(content, true);
         mailSender.send(message);
     }
 }

controller测试代码

 import com.hyp.emailtest.service.EmailService;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.mail.MailException;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RestController;

 import javax.mail.MessagingException;

 @RestController
 @RequestMapping("Mail")
 public class EmailController {

     @Autowired
     private EmailService emailService;

     //发送简单文本邮件
     @RequestMapping(value = "send", method = RequestMethod.GET)
     public void Send() {
         String To = "test@xxxx.com";
         String Subject = "Java发邮件测试";
         String Content = "这是一封来自JavaMailSender自动发送的测试邮件";
         try {
             emailService.sendSimpleMail(To, Subject, Content);
             System.out.println("发送成功");
         } catch (MailException ex) {
             System.out.println("发送失败");
             System.out.println(ex.toString());
         }
     }

     //发送富文本邮件
     @RequestMapping(value = "sendImg", method = RequestMethod.GET)
     public void SendWithImg() {
         String to = "test@xxxx.com";
         String subject = "Java发邮件测试";
         String rscId = "img1";
         String content = "<html><body><img width='250px' src=\'cid:" + rscId + "\'></body></html>";
         //图片路径，这里要写绝对路径
         String imgPath = "E:\\11.jpg";
         try {
             emailService.sendRichTextMail(to, subject, content, imgPath, rscId);
             System.out.println("发送成功");
         } catch (MessagingException ex) {
             System.out.println("发送失败");
             System.out.println(ex.toString());
         }
     }

     //发送HTML邮件
     @RequestMapping(value = "sendHtml", method = RequestMethod.GET)
     public void SendWithHtml() {
         String to = "test@xxxx.com";
         String subject = "Java发邮件测试";
         String content = "<html><head></head><body><h3>这是html邮件。。。</h3></body></html>";
         try {
             emailService.sendHtmlMail(to, subject, content);
             System.out.println("发送成功");
         } catch (MessagingException ex) {
             System.out.println("发送失败");
             System.out.println(ex.toString());
         }
     }
 }

在controller中要注意的是，需要把EmailService注入，不能实例化，否则在Service类中@Value()注解会找不到spring.mail.username的值，

原因请参考：https://stackoverflow.com/questions/39047333/spring-boot-value-properties

我的理解是，手动实例化(new)类的实例是JVM做的事情，SpringBoot并没有参与，所以Value注解将被忽略，字段自然取不到值。

还有被注解的字段不能是static，SpringBoot依赖注入不支static的变量注入。原因是Spring依赖注入的底层原理还是利用反射方式来创建对象。而static修饰的字段、变量在JVM加载类的时候就已经创建，存在于方法区，是类的属性而不是对象的属性，Spring是基于对象层面的依赖注入。