来自 URL : "FileNotFoundException" 的带有 FileSystemResource 的 Java 邮件附件

Question

我正在使用 Java Mail 发送带有附件的电子邮件。附件不是本地存储在应用程序下，而是从 URL 动态提取。

    List<FileSystemResource> fileSystemResources = new ArrayList<FileSystemResource>();
    fileSystemResources.add(new FileSystemResource(
             "http://myapp-dev.host.com/app/File1.PDF"));

    //... Prepare email with dynamic-URL-obtained attachments...
    MimeMessage msg = mailSender.createMimeMessage();
    MimeMessageHelper message = new MimeMessageHelper(msg, true, "UTF-8");
    for (FileSystemResource fileSystemResource : fileSystemResources) {
            message.addAttachment(fileSystemResource.getFilename(), fileSystemResource);
    }

    //... at the end, send
    mailSender.send(msg);

资源存在，我可以独立验证它:例子，http://myapp-dev.host.com/app/File1.PDF

但是我抛出以下异常:

java.lang.Exception]: org.springframework.mail.MailSendException: 
  Failed messages: javax.mail.MessagingException: IOException while sending message;
  nested exception is:
    java.io.FileNotFoundException: http://myapp-dev.host.com/app/File1.PDF 
    (No such file or directory);

我见过的大多数示例都将 FileSystemResource 用于本地文件，而不是 URI 资源。代码有问题吗？

Answer 1

FileSystemResource 的 JavaDoc说:

Resource implementation for java.io.File and java.nio.file.Path handles with a file system target. Supports resolution as a File and also as a URL.

它仅处理 file:// URL，而不是 HTTP URL。

对于任何 URL(HTTP 和 file://)，您可以使用 UrlResource :

Resource implementation for java.net.URL locators. Supports resolution as a URL and also as a File in case of the "file:" protocol.