【javaMail】java创建Excel表不生成本地xls文件，直接通过ByteArrayOutputStream存入javamail邮件附件后发送至相应邮箱_outputstream 导出excel没有生成下载文件

前段时间猫哥遇到一个需求，通过java生成Excel后，利用javamail附件形式发送给相应邮箱。

查阅大量资料后发现，大部分的解决方案都是生成本地xls文件，再通过文件名和文件地址传给javamail的附件内。很明显，这样的解决方案不合理，会占用服务器大量的存储空间和IO，最理想的方法是不生成本地xls文件，直接通过流的形式传给javamail附件。

摸索了一阵后，猫哥找到了解决方案，在这里记录一下。

大致的思路就是：利用ByteArrayOutputStream直接将excel文件传入邮件附件。

代码如下：

ByteArrayOutputStream os = new ByteArrayOutputStream();
HSSFWorkbook  wb = new HSSFWorkbook();
HSSFSheet sheet = wb.createSheet("new sheet");
 
/**此处省去对EXCEL表内容和格式的详细编码过程**/
 
try {
	wb.write(os);
} catch (IOException e) {
	e.printStackTrace();
}
 
ByteArrayInputStream a = new ByteArrayInputStream(os.toByteArray());
 
String uuid = "test.xls";
//指明让哪个smtp转发
SendMailService themail = new SendMailService("smtp.163.com");
//将ByteArrayInputStream直接存入mail的附件内
themail.addFileAffix(a,uuid)

邮件服务SendMailService 的具体代码如下：

package com.catchgo.devicejob.service;
 
import com.xxl.job.core.log.XxlJobLogger;
 
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.*;
import javax.mail.internet.*;
import javax.mail.util.ByteArrayDataSource;
import java.io.InputStream;
import java.util.Properties;
 
/**
 * @Description:
 * @Author: Li Yacheng
 * @Date: 2020/6/24 14:06
 */
public class SendMailService {
    private MimeMessage mimeMsg;  //MIME邮件对象
 
    private Session session; //邮件会话对象
    private Properties props; //系统属性
    private boolean needAuth = false;  //smtp是否需要认证
 
    private String username = "";  //smtp认证用户名和密码
    private String password = "";
 
    private Multipart mp; //Multipart对象，邮件内容，标题、附件等内容均添加到其中后在生成Multipart对象
 
    public SendMailService(String smtp) {
        setSmtpHost(smtp);
        createMimeMessage();
    }
 
    /**
     *
     * @param hostName
     */
    private void setSmtpHost(String hostName) {
        System.out.println("设置系统属性：mail.smtp.host = "+hostName);
        if(props == null){
            props = System.getProperties();  //获得系统属性对象
        }
        props.put("mail.smtp.host", hostName);  //设置SMTP主机
 
        props.put("mail.smtp.port", "465");
        props.put("mail.smtp.socketFactory.port", "465");
        props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
        props.put("mail.smtp.socketFactory.fallback", "false");
 
    }
 
    /**
     *
     * @return boolean
     */
    private boolean createMimeMessage() {
        try{
            System.out.println("准备获取邮件会话对象");
            session = Session.getDefaultInstance(props, null);  //获取邮件会话对象
        }catch(Exception e){
            System.out.println("获取邮件会话对象错误!" + e);
            return false;
        }
 
        System.out.println("准备创建MIME邮件对象！");
        try{
            mimeMsg = new MimeMessage(session); //创建MIME邮件对象
            mp = new MimeMultipart("mixed"); //mp 一个multipart对象
            return true;
        }catch(Exception e){
            System.out.println("创建MIME邮件对象失败!" + e);
            return false;
        }
    }
 
    /**
     *
     * @param need boolean
     */
    public void setNeedAuth(boolean need){
        System.out.println("设置smtp身份认证：mail.smtp.auth =" + need);
        if(props == null){
            props = System.getProperties();
        }
 
        if(need){
            props.put("mail.smtp.auth", "true");
            props.put("mail.smtp.starttls.enable", "true");
            props.put("mail.smtp.starttls.required", "true");
        }else{
            props.put("mail.smtp.auth", "false");
        }
    }
 
    /**
     *
     * @param name String
     * @param pass String
     */
    public void setNamePass(String name,String pass){
        System.out.println("程序得到用户名和密码");
        username = name;
        password = pass;
    }
 
    /**
     *
     * @param mailSubject String
     * @return boolean
     */
    public boolean setSubject(String mailSubject){
        System.out.println("设置邮件主题！");
        try{
            mimeMsg.setSubject(MimeUtility.encodeText(mailSubject, "UTF-8", "B"));
            return true;
        }catch(Exception e){
            System.out.println("创建邮件主题失败!" + e);
            XxlJobLogger.log("创建邮件主题失败!" + e);
            return false;
        }
    }
    /**
     *
     * @param mailBody String
     * @return boolean
     */
    public boolean setBody(String mailBody){
        System.out.println("设置邮件主体！");
        try{
            BodyPart bp = new MimeBodyPart();
            bp.setContent(mailBody,"text/html;charset=gbk");
            mp.addBodyPart(bp);
            return true;
        }catch(Exception e){
            System.out.println("创建邮件正文发送失败!" + e);
            XxlJobLogger.log("创建邮件正文发送失败!" + e);
            return false;
        }
    }
 
	/**
     *
     * @param InputStream attachmentByteArray
     * @param String tittle
     * @return boolean
     */
    public boolean addFileAffix(InputStream attachmentByteArray, String tittle){
        try{
 
            MimeBodyPart  bp = new MimeBodyPart();
            //DataSource files =  new ByteArrayDataSource(attachmentByteArray, "application/msword");
            DataSource files =  new ByteArrayDataSource(attachmentByteArray, "application/vnd.ms-excel;charset=UTF-8");
 
            bp.setDataHandler(new DataHandler(files));
            bp.setFileName(MimeUtility.encodeText(tittle));
            mp.addBodyPart(bp);
 
            return true;
        }catch(Exception e){
            //System.err.println("添加邮件：" + fileName +" 发生错误！"+ e);
            return false;
        }
    }
 
    public boolean setFrom(String from){
        System.out.println("设置发件人！");
        try{
            mimeMsg.setFrom(new InternetAddress(from));   //设置发件人
            return true;
        }catch(Exception e){
            XxlJobLogger.log("设置发件人失败!" + e);
            return false;
        }
    }
 
    /**
     *
     * @param to String
     * @return boolean
     */
    public boolean setTo(String to,String email){
        System.out.println("设置收件人！");
        if(to == null){
            return false;
        }
        try{
            mimeMsg.addRecipients(Message.RecipientType.TO, InternetAddress.parse(to));   //发送别人
            mimeMsg.addRecipients(Message.RecipientType.CC, InternetAddress.parse(email));  //抄送自己
            return true;
        }catch(Exception e){
            XxlJobLogger.log("设置收件人失败！"+e);
            return false;
        }
    }
    /**
     *
     * @param copyto String
     * @return boolean
     */
    public boolean setCopyTo(String copyto){
        System.out.println("发送附件到");
        if(copyto == null){
            return false;
        }
 
        try{
            mimeMsg.setRecipients(Message.RecipientType.CC, (Address[])InternetAddress.parse(copyto));
            return true;
        }catch(Exception e){
            return false;
        }
    }
 
    public boolean sendout(){
        try{
            mimeMsg.setContent(mp);
 
            mimeMsg.saveChanges();
            System.out.println("正在发送邮件...");
 
            Session mailSession = Session.getInstance(props,null);
            Transport transport = mailSession.getTransport("smtp");
            transport.connect((String)props.get("mail.smtp.host"), username,password);
 
//            transport.sendMessage(mimeMsg, mimeMsg.getRecipients(Message.RecipientType.TO));
            transport.sendMessage(mimeMsg, mimeMsg.getAllRecipients());
 
            System.out.println("邮件发送成功！");
            transport.close();
            return true;
        }catch(Exception e){
            System.out.println("邮件发送失败！" + e);
            XxlJobLogger.log("邮件发送失败！"+e);
            return false;
        }
    }
}

以上即可实现不生成本地文件，直接通过javamail附件发送邮件的功能。