如何将远程文件路径转换为Base64用于邮件附件？

你的问题出在给attachments[0].content赋值的是data URI格式的字符串，但SendGrid的API要求的是纯Base64编码的文件内容，不需要data:${contentType};base64,这个前缀。

修正步骤： #

• 去掉data:前缀和MIME类型部分，直接把Base64编码后的字符串赋值给content
• 确保filename带上正确的文件扩展名（比如.png），方便收件方识别文件类型

修正后的关键代码片段： #

await axios.get(attachmentUrl, {responseType: "arraybuffer"})
  .then(response => {
    const contentType = response.headers["content-type"];
    const dataString = Buffer.from(response.data).toString("base64");
    // 直接赋值纯Base64内容，去掉data URI前缀
    emailOptions.attachments[0].content = dataString;
    emailOptions.attachments[0].type = contentType;
    // 修正文件名，带上扩展名
    emailOptions.attachments[0].filename = 'Cover_Go_Studio.png';
  });

完整修正后的控制器代码： #

'use strict'
const axios = require("axios");

module.exports = {
  
  send: async (ctx) => {
    const body = ctx.request.body
    const sendTo = 'vupd@hihi.com'
    strapi.log.debug(`Trying to send an email to ${sendTo}`)
  
    const attachmentUrl ='https://cms.gstech.space/uploads/Cover_Go_Studio_204fca7084.png'
    try {
      const emailOptions = {
        to: sendTo,
        subject: 'Test',
        text:"Test",
        attachments:[{
          content: undefined,
          filename: 'Cover_Go_Studio.png',
          type: undefined,
          disposition: "attachment",
        }]
      };
  
      await axios.get(attachmentUrl, {responseType: "arraybuffer"})
        .then(response => {
          const contentType = response.headers["content-type"];
          const dataString = Buffer.from(response.data).toString("base64");
          emailOptions.attachments[0].content = dataString;
          emailOptions.attachments[0].type = contentType;
        });
  
      await strapi.plugins['email'].services.email.send(emailOptions)
      strapi.log.debug(`Email sent to  ${sendTo}`)
      ctx.send({ message: 'Email sent' })
    } catch (err) {
      strapi.log.error(`Error sending email to ${sendTo}`, err)
      ctx.send({ error: 'Error sending email' })
    }
  }
}

补充说明： #

• 远程文件不能用fs.readFileSync是正常的，fs模块仅能读取本地文件系统的文件，你用axios请求远程资源并转arraybuffer的思路是正确的
• 若axios请求失败，可在catch块中增加针对性的日志输出，便于排查网络或资源访问问题

内容的提问来源于stack exchange，提问作者BinChanhKun