cannot be resolved to absolute file path because it does not reside in the file system 问题解决

问题原因

 Resource resource = new ClassPathResource("static/test.xlsx");
 if (resource.exists()) {
     try {
         File file = resource.getFile();
         ...
     } catch (IOException e) {
         throw new RuntimeException(e);
     }
 }

将test.xlsx文件放到resources的static目录下，当使用以上代码读取文件内容时，在本地运行正常，打成jar包上服务器之后报异常信息cannot be resolved to absolute file path because it does not reside in the file system

本地调试

通过打断点的形式来分析下问题出现的原因，该方法会进入AbstractFileResolvingResource类

public File getFile() throws IOException {
	URL url = this.getURL();
	return url.getProtocol().startsWith("vfs") ? AbstractFileResolvingResource.VfsResourceDelegate.getResource(url).getFile() : ResourceUtils.getFile(url, this.getDescription());
}

因为url.getProtocol()为file，所以会走ResourceUtils.getFile(url, this.getDescription());，进入该方法

public static File getFile(URL resourceUrl, String description) throws FileNotFoundException {
        Assert.notNull(resourceUrl, "Resource URL must not be null");
        if (!"file".equals(resourceUrl.getProtocol())) { //注意注意，这是“代码块”
            throw new FileNotFoundException(description + " cannot be resolved to absolute file path because it does not reside in the file system: " + resourceUrl);
        } else {
            try {
                return new File(toURI(resourceUrl).getSchemeSpecificPart());
            } catch (URISyntaxException var3) {
                return new File(resourceUrl.getFile());
            }
        }
    }

因为 resourceUrl.getProtocol() 为File，说明该url 地址对应的资源是文件，所以直接返回这个文件。

远程调试

将jar包发布到服务器之后，用本地远程调试远程代码，我们会发现此时url.getProtocol()为jar，所以会在“代码块”处抛出异常。
cannot be resolved to absolute file path because it does not reside in the file system

解决方案

一、将要使用的文件直接放到服务器的固定目录下，直接从服务器中获取而不是从jar包获取；
二、通过流来获取jar里面的文件；

Resource resource = new ClassPathResource("static/test.xlsx");
// 以流的形式读取文件内容
try (InputStream inputStream = resource.getInputStream()) {
    return FileCopyUtils.copyToByteArray(inputStream);
}