When uploading files, use multipartfile Transferto() saves the file to the local path:

report errors:

java.io.IOException: java.io.FileNotFoundException: C:\Users\XXXXX\AppData\Local\Temp\tomcat. 8350081478984499756.8080\work\Tomcat\localhost\ROOT\app\file\xxxx. Xlsx (the system cannot find the specified path.)

    @Override
    public String store(MultipartFile file, String fileName) throws IOException {

        String destPath "/app/file/";
        File filePath = new File(destPath);
        File dest = new File(filePath, fileName);
        if (!filePath.exists()) {
            filePath.mkdirs();
        }
        try {
            file.transferTo(dest);
            log.info("file save success");
        } catch (IOException e) {
            log.error("File upload Error: ", e);
            throw e;
        }
        return dest.getCanonicalPath();
    }

Cause analysis:

file. When the transferto method is called, it is judged that if it is a relative path, the temp directory is used as the parent directory
so it is saved in the temporary work directory of Tomcat.

Solution:

Use absolute path: filepath.getAbsolutePath()

    @Override
    public String store(MultipartFile file, String fileName) throws IOException {

        String destPath "/app/file/";
        File filePath = new File(destPath);
        
        // Convert to absolute path
        File dest = new File(filePath.getAbsolutePath(), fileName);
        if (!filePath.exists()) {
            filePath.mkdirs();
        }
        try {
            file.transferTo(dest);
            log.info("file save success");
        } catch (IOException e) {
            log.error("File upload Error: ", e);
            throw e;
        }
        return dest.getCanonicalPath();
    }

Supplement:

You can also file Getbytes() gets the byte array, or file Getinputstream() performs stream data operation and writes it to disk.

Access to uploaded files

spring:
	resources:
    	static-locations: file:/app/file/  #Access external system resources and map the files in this directory to the system

or

import java.io.File;
import java.util.concurrent.TimeUnit;

import org.springframework.context.annotation.Configuration;
import org.springframework.http.CacheControl;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        String absolutePath = new File("/app/file/").getAbsolutePath();
        
        registry.addResourceHandler("/upload/**") // External Access Addresses
                .addResourceLocations("file:" + absolutePath)// SpringBoot needs to add the file protocol prefix
                .setCacheControl(CacheControl.maxAge(30, TimeUnit.MINUTES));// set the browser cache
    }
}