Spring Boot 打包JAR 後獲取不了classpath下文件| java.io.filenotfoundexception: class path resource

在製作發送郵件的程式時，所遇到的坑

本地端運行沒問題但是打包成Jar要用docker跑image時報錯

java.io.filenotfoundexception: class path resource [static/題庫.pdf] cannot be resolved to absolute file path because it does not reside in the file system: jar:file:/docker-demo.jar!/boot-inf/classes!/static/%e9%a1%8c%e5%ba%ab.pdf at org.springframework.util.resourceutils.getfile(resourceutils.java:217) at org.springframework.core.io.abstractfileresolvingresource.getfile

因为打包後Spring會去訪問系統的路徑，但無法訪問JAR中的路徑。
必須使用resource.getInputStream()

寫入複製

ClassPathResource classPathResource = new ClassPathResource("檔案");
InputStream inputStream = classPathResource.getInputStream();
File somethingFile = File.createTempFile("高命中率題庫", ".pdf");//自動創建在默認的臨時文件夾中的空文件
try {
    FileUtils.copyInputStreamToFile(inputStream, somethingFile);
} 
finally {
    IOUtils.closeQuietly(inputStream);
}
   messageHelper.addAttachment("題庫.pdf", somethingFile);
   //附件
mailSender.send(mimeMessage);

讀取

ClassPathResource resource = new ClassPathResource("檔案");
InputStream inputStream = resource.getInputStream();
IOUtils.readLines(inputStream).forEach(System.out::println);

希望這篇文章能夠幫助到你(妳)

如有錯誤指正

I hope you found this guide helpful. If not, then please let me know either in the comments below, I’m Albert