在Spring Boot中来发送邮件是很方便的事情，只需要添加对应的依赖jar,然后配置邮箱服务器地址和账号就可以实现邮件的发送。本示例使用JDK1.8, Spring Boot 1.5.9.RELEASE来演示邮件的发送。

1.创建项目

可以通过 http://start.spring.io/ 来快速创建项目，选择mail模块。或者手动创建，并添加对应的依赖。
所需的mail jar:

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

2.配置信息

本测试实例以阿里的邮箱来演示，不同邮箱服务器的host需要修改：

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spring:
  mail:
    properties:
      mail:
        smtp:
          connectiontimeout: 5000
          timeout: 3000
          writetimeout: 5000
          auth: true
          starttls:
            enable: true
    efault-encoding: UTF-8  #设置编码 防止乱码
    protocol: smtp
    host: smtp.mxhichina.com
    port: 25
    username: #邮箱帐号
    password: #邮箱密码
  messages:
    encoding: UTF-8
    basename: com/devnp/message/MailMessage

3.发送一般邮件

发送邮件使用 org.springframework.mail.javamail.JavaMailSender 来完成, 首先注入JavaMailSender，完整代码 com.devnp.springbootemaildemo.email.SimpleMailSend.java：

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@Autowired
private JavaMailSender mailSender;

@Value("${spring.mail.username}")
private String sender; //发送地址

@Autowired
private ResourceLoader resourceLoader;

发送给单一的用户：

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/**
 * 发送给单一的用户
 * @param toMail
 * @param content
 */
public void simpleSend(String toMail, String subject, String content) {
	SimpleMailMessage message = new SimpleMailMessage(); 
	
	message.setTo(toMail);
	message.setSubject(subject);
	message.setText(content);
	message.setFrom(sender); //确保发送邮件地址与认证地址，如果不一致， 一些邮箱服务器会退信
	
	this.mailSender.send(message);
}

发送 给多个地址，并且抄送多人，同时隐身抄送给多个人：

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/**
 * 发送 给多个地址，并且抄送多人，同时隐身抄送给多个人
 * @param toMails 收件人地址
 * @param ccMails 抄送人地址
 * @param bccMails 隐形抄送地址 不会出现在地址栏
 * @param subject 标题
 * @param content 内容
 */
public void simpleSend(String [] toMails, String [] ccMails, String [] bccMails, String subject, String content) {
	SimpleMailMessage message = new SimpleMailMessage(); 
	
	message.setTo(toMails);
	message.setCc(ccMails);
	message.setBcc(bccMails);
	message.setSubject(subject);
	message.setText(content);
	message.setFrom(sender); //确保发送邮件地址与认证地址，如果不一致， 一些邮箱服务器会退信
	
	this.mailSender.send(message);
}
使用 MimeMessagePreparator：
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/**
 * 使用 MimeMessagePreparator  回掉接口來发送html 同时 也可以使用 MimeMessageHelper
 * @param toMail
 * @param subject
 * @param content html
 */
public void sendWithHtml(String toMail, String subject, String content) {
	
	MimeMessagePreparator preparator = new MimeMessagePreparator() {
        public void prepare(MimeMessage mimeMessage) throws Exception {
            mimeMessage.setRecipient(Message.RecipientType.TO, new InternetAddress(toMail));
            mimeMessage.setSubject(subject);
            mimeMessage.setFrom(new InternetAddress(sender));
            mimeMessage.setText(content, StandardCharsets.UTF_8.name(), "html");
        }
    };

    this.mailSender.send(preparator);
}

4.发送带有附件的邮件：

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/**
 * 发送带有附件的邮件
 * @param toMail
 * @param subject
 * @param content
 * @param files
 * @throws MessagingException 
 */
public void sendWithAttachemnt(String toMail, String subject, String content, List<String> files) throws MessagingException{
	MimeMessage message = mailSender.createMimeMessage();
	
	MimeMessageHelper helper = new MimeMessageHelper(message, true);
	
	helper.setTo(toMail);
	helper.setSubject(subject);
	helper.setText(content); //支持发送html setText(String text, boolean html)
	helper.setFrom(sender);
	
	for (int i = 0; i < files.size(); i++) {
		
		Resource resource =  resourceLoader.getResource(files.get(i));
				
		helper.addAttachment(resource.getFilename() , resource);
	}
	
	this.mailSender.send(message);
}

5.发送模板邮件

使用模板来发送邮件，和普通邮件的不同之处在于需要设计模板，然后使用模板引擎对模板进行渲染，渲染的之后的数据在发送，以thymeleaf为例：
首先添加对应的依赖jar:

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

在Spring Boot 1.5.9.RELEASE的版本中，默认引入的thymeleaf的版本为2.1.6.RELEASE，为了适应text形式的模板，所以需要将thymeleaf提高到3.X，所以在properties中增加如下：

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<thymeleaf.version>3.0.2.RELEASE</thymeleaf.version>
<thymeleaf-layout-dialect.version>2.1.1</thymeleaf-layout-dialect.version>

1.模板配置

Spring Boot 默认有配置模板引擎和解析器，这里为了不冲突默认的，单独来配置模板引擎和解析器, 完整配置代码 com.devnp.springbootemaildemo.email.config.SpringMailConfig：

HTML 模板引擎和解析器：

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@Bean
public TemplateEngine htmlEmailTemplateEngine() {
    final SpringTemplateEngine templateEngine = new SpringTemplateEngine();
    // Resolver for TEXT emails
    //templateEngine.addTemplateResolver(textTemplateResolver());
    // Resolver for HTML emails (except the editable one)
    templateEngine.addTemplateResolver(htmlTemplateResolver());
    // Resolver for HTML editable emails (which will be treated as a String)
    //templateEngine.addTemplateResolver(stringTemplateResolver());
    // Message source, internationalization specific to emails
    //templateEngine.setTemplateEngineMessageSource(emailMessageSource());
    
    return templateEngine;
}

/**
 * html 模板解析器
 * @return
 */
private ITemplateResolver htmlTemplateResolver() {
    final ClassLoaderTemplateResolver templateResolver = new ClassLoaderTemplateResolver();
    //templateResolver.setOrder(Integer.valueOf(2));
    //templateResolver.setResolvablePatterns(Collections.singleton("html/*"));
    templateResolver.setPrefix("/templates/");
    templateResolver.setSuffix(".html");
    templateResolver.setTemplateMode(TemplateMode.HTML);
    templateResolver.setCharacterEncoding(StandardCharsets.UTF_8.name());
    templateResolver.setCacheable(false);
    return templateResolver;
}

TEXT 模板引擎和解析器：

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@Bean
public TemplateEngine textEmailTemplateEngine() {
    final SpringTemplateEngine templateEngine = new SpringTemplateEngine();
    // Resolver for TEXT emails
    templateEngine.addTemplateResolver(textTemplateResolver());
    // Resolver for HTML emails (except the editable one)
    //templateEngine.addTemplateResolver(htmlTemplateResolver());
    // Resolver for HTML editable emails (which will be treated as a String)
   // templateEngine.addTemplateResolver(stringTemplateResolver());
    // Message source, internationalization specific to emails
    //templateEngine.setTemplateEngineMessageSource(emailMessageSource());
    
    return templateEngine;
}

/**
 * TEXT 模板解析器
 * @return
 */
private ITemplateResolver textTemplateResolver() {
    final ClassLoaderTemplateResolver  templateResolver = new ClassLoaderTemplateResolver();
    //templateResolver.setOrder(Integer.valueOf(1)); //优先级
    //templateResolver.setResolvablePatterns(Collections.singleton("text/*")); //文件类型
    templateResolver.setPrefix("/templates/"); //模板文件开始
    templateResolver.setSuffix(".txt"); //模板文件结尾
    templateResolver.setTemplateMode(TemplateMode.TEXT); //模板模型
    templateResolver.setCharacterEncoding(StandardCharsets.UTF_8.name()); //编码
    templateResolver.setCacheable(false); //缓存
    return templateResolver;
}

2.html模板

templates\mail\html\mail-hello.html

[code lang=”html”]

http://www.denvp.com
, 
<div>
    <p th:text="#{msg.content}"></p>
</div>

<div>
    <p th:text="#{msg.thank}"></p>
    <em><a href="http://www.denvp.com">www.denvp.com</a></em>
</div>
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设置资源文件，用于对静态信息的展示, 同时也可以对多语言的支持，关于<a href="http://www.devnp.com/2018/04/03/spring-boot-%e5%9b%bd%e9%99%85%e5%8c%96-spring-boot-internationalization-demo/" rel="noopener" target="_blank">Spring Boot 国际化</a> :
<em>com\devnp\message\MailMessage_zh_CN.properties</em>

```text
msg.hello = 你好
msg.thank = 感谢
msg.content = 这是一封测试来自模板的邮件

3.text模板

templates\mail\text\mail-hello.txt

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[(#{msg.hello})] [( ${name} )],

[# th:if="${name.length() gt 10}"] 你的名字太长啦 [/]

 [( ${#dates.format(subscriptionDate)} )]

你的爱好:
[# th:each="hobby : ${hobbies}"]
 - [( ${hobby} )]
[/]

[(#{msg.content})]

4.发送邮件

com.devnp.springbootemaildemo.email.TemplateMailSend.java

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/**
 * 
 */
package com.devnp.springbootemaildemo.email;

import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.Date;
import java.util.Locale;

import javax.mail.MessagingException;
import javax.mail.internet.MimeMessage;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.stereotype.Component;
import org.thymeleaf.TemplateEngine;
import org.thymeleaf.context.Context;

/**
 * @author duliu
 *
 */
@Component
public class TemplateMailSend {
	
	public Logger log = LoggerFactory.getLogger(getClass());
	
	@Autowired
    private TemplateEngine textEmailTemplateEngine;
	
	@Autowired
    private TemplateEngine htmlEmailTemplateEngine;

	@Autowired
	private JavaMailSender mailSender;
	
	@Value("${spring.mail.username}")
	private String sender;
	
	@Autowired
	private ResourceLoader resourceLoader;
	
	/**
	 *  使用Html模板来生产发送消息
	 * @param toMail
	 * @param subject
	 * @param file
	 * @throws MessagingException 
	 */
	public void sendWithThymeleafHtmlTemplate(String toMail, String subject, String file, String recipientName, String imageResourceName) throws MessagingException {
		MimeMessage message = mailSender.createMimeMessage();
		
		MimeMessageHelper helper = new MimeMessageHelper(message, true, StandardCharsets.UTF_8.name());
		
		helper.setTo(toMail);
		helper.setSubject(subject);
		helper.setFrom(sender);
		
		//设置方言环境
		final Context ctx = new Context(Locale.SIMPLIFIED_CHINESE); 
		
		ctx.setVariable("name", recipientName);
		ctx.setVariable("imageResourceName", imageResourceName);
		
		String htmlContent = this.htmlEmailTemplateEngine.process(file, ctx);
		
		Resource resource =  resourceLoader.getResource("classpath:static/logo.png");
		
		helper.setText(htmlContent, true);
		
		helper.addInline(imageResourceName, resource);
		
		log.info(htmlContent);
		
		this.mailSender.send(message);
	}

	/**
	 * 使用Text模板来生产发送消息
	 * @param toMail
	 * @param subject
	 * @param file
	 * @param recipientName
	 * @throws MessagingException
	 */
	public void sendWithThymeleafTextTemplate(String toMail, String subject, String file, String recipientName) throws MessagingException {
		MimeMessage message = mailSender.createMimeMessage();
		
		MimeMessageHelper helper = new MimeMessageHelper(message, true, StandardCharsets.UTF_8.name());
		
		helper.setTo(toMail);
		helper.setSubject(subject);
		helper.setFrom(sender);
		
		//设置方言环境
		final Context ctx = new Context(Locale.SIMPLIFIED_CHINESE); 
		
		ctx.setVariable("name", recipientName);
		ctx.setVariable("subscriptionDate", new Date());
		ctx.setVariable("hobbies", Arrays.asList("吃", "吃", "吃"));
		
		String txtContent = this.textEmailTemplateEngine.process(file, ctx);
		
		helper.setText(txtContent);
		
		log.info(txtContent);
		
		this.mailSender.send(message);
	}
}

5.测试

编写相应的单元测试代码，为了不显示过多的代码篇幅：

com.devnp.springbootemaildemo.email.SimpleMailSendTests.java
com.devnp.springbootemaildemo.email.TemplateMailSendTests.java

6.参考

https://docs.spring.io/spring/docs/4.3.16.RELEASE/spring-framework-reference/htmlsingle/#mail
https://www.thymeleaf.org/doc/articles/springmail.html

7.代码下载

spring-boot-email-demo.zip